Upward and downward colonization of vegetation following the retreat of the Aneto glacier, since the Little Ice Age

Upward and downward colonization of vegetation following the retreat of the Aneto glacier, since the Little Ice Age | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Upward and downward colonization of vegetation following the retreat of the Aneto glacier, since the Little Ice Age Pablo Tejero, Cesar Deschamps-Berger, Nahia Carretero-Roque, Juan Ignacio Lopez-Moreno, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8663348/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Glacier surface is decreasing worldwide and deglaciated land provides a unique opportunity to study plant colonization and primary ecological succession in alpine ecosystems. Most previous research on the topic has been conducted in strongly glaciated regions hosting the most important glacier systems. Contrastingly, little research has been conducted in thermic mountains with relict glaciers near extinction like those of the Pyrenees. The highest peak in the Pyrenees, Aneto, hosts a glacier that has dramatically shrunk in recent decades, and is currently restricted to upper slopes near the ridgeline. To understand plant succession and colonization in a system representative of relictual thermic glaciers, we conducted vegetation surveys along the deglaciation chronosequence of the Aneto glacier, from the Little Ice Age (LIA) to date. We identified vascular plant species present in 60 plots at 6 different sites along the deglaciation gradient, recording 65 different species in total. Plant composition was different between the deglaciated area and nearby control surveys conducted in adjacent unglaciated areas where diversity was higher. Moreover, plant diversity decreased towards recently deglaciated areas, and plant composition became more stochastic. Interestingly, we found evidence that colonization in the lower part of the deglaciated slope was based on the species pool of non glaciated areas below the glacier and colonization of the upper part was also strongly influenced by downward colonization from species native to the ridges. Consequently, although the altitude is not the main driver of the colonization process along the chronosequence, it has a relevant role in determining the species source. Glacial retreat Chronosequence Primary plant succession Aneto glacier Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction The global glacier surface has been shrinking throughout the Holocene, but human-driven climate change in recent decades has greatly accelerated this decline (Hock et al. 2019 ; Losapio et al. 2025 ). The increase in temperatures and the related decrease in snow precipitation have led to a negative mass balance of most glaciers across the planet (Dussaillant et al. 2025 ; The GlaMBIE Team et al. 2025 ). Consequently, continental ice mass is decreasing with the associated loss of water reservoirs, which may have a strong influence on multiple ecosystem services and an impact on the economical and social development of human societies (Schuster et al. 2024). In this context of massive glacier retreat worldwide, temperate mountain ranges are the most prone to lose their permanent ice cover (Dussaillant et al.2025). The disappearance of glaciers alters the water regime of tributary drainages, which may lead to cascading ecological changes. In the alpine and nival vegetation belt ( sensu Withttaker, 1978), new ice-free surfaces become available for life colonization and the establishment of novel alpine communities, buffering the overall threat to these ecosystems under current climate warming (Bosson et al. 2023 ; Ficetola et al. 2024 ). This ecological context of primary ecological succession, where vegetation colonizes a recently uncovered barren rocky landscape, provides a unique setting to study the fundamental processes of vegetation development (Bosson et al. 2023 ). The Pyrenees are a great example of temperate but still glaciated mountains. In 2023 there were fifteen small relict glaciers restricted to the upper north faces of the highest massifs (Izagirre et al. 2024 ). Monitoring and modeling indicate accelerated shrinkage of all ice-covered area with an estimated complete disappearance of Pyrenean glaciers by 2034 (López-Moreno et al. 2025 ). The Aneto glacier is of particular interest because it is the largest glacier in the Pyrenees and has experienced a dramatic surface decrease since the end of the Little Ice Age (LIA, circa 1850), opening hectares of ice-free surfaces for pioneering organisms to colonize. The Aneto-Maladeta massif has lost 88% (6.22 km²) of its glaciated area between 1850 and 2021 (Vidaller et al. 2025 ), which provided barren rocky surfaces available for plant colonization at different dates along the chronosequence of glacier retreat. There is solid evidence that during Pleistocene glacial cycles, cold adapted biota recurrently expanded during glaciations and further became restricted into polar regions and high mountains during interglacial periods (Hewitt 1999 ; Parisod 2008 ; Wootton et al. 2025 ). These dynamics have shaped the biodiversity currently found in the Northern hemisphere mountains. In this scenario, the species had three options: migrate, adapt if they could not migrate, or get extinct if they could not migrate nor adapt efficiently (Nogués-Bravo et al. 2018). Therefore, within the extant mountain species, we expect a filter towards good migration ability (Tovar et al. 2020 ) or strong alpine specialization leading to local endemicity (Kadereit 2024 ). During periods of glacial retreat, new opportunities for alpine plants to colonize previously ice-covered substrates arise, initiating a primary succession process that may evolve towards more complex communities with time and soil development (Dentant et al. 2024 ; Leonelli et al. 2024 ; Losapio et al. 2025 ). Plants are key components of ecosystems, for instance, as primary producers fixing CO 2 , assimilating inorganic nutrients, creating soil or providing shelter and nutrition to other species. Consequently, their role in the colonization of recently deglaciated soils is crucial (Velasquez Casallas et al. 2025 ). In plants, gene flow can occur through pollen or seeds, but physical migration to occupy new territories when ice cover fluctuates is limited to seed dispersal. Although some lineages like Asteraceae present evident long distance dispersal syndromes (Mandel et al. 2019 ), not all alpine plant species do (Tovar et al. 2020 ). Plant colonization after glacial retreat has been investigated in arctic and subarctic glaciers as well as in strongly glaciated mountain ranges such as the Andes (Anthelme et al. 2022 ) and the Alps (Bayle et al. 2023 ; Nota et al. 2025 ). However, research is still lacking in strongly deglaciated, warmer mountains where the persistence of glaciers in coming decades is not climatically sustainable (López-Moreno et al. 2025 ) and where, consequently, plant colonization is expected to be favoured and intense. Besides, some relict of glaciers often resist these temperate mountains in steep slopes sheltered from solar radiation in the upper slopes with northern aspect, where plant colonization is supposedly more challenging. Opposite to the glaciers representing most study cases with ice tongues running through valleys with low or moderate slope (Vetaas 1994 ; Mathews and Vater 2015; Fickert 2020 ; Bayle et al. 2023 ; Cantera et al. 2024 ; Tanner et al. 2024 ), the retreat of steep glaciers in more thermic regions, like the Pyrenees, creates ice-free areas with strong altitudinal gradients where colonization dynamics remain poorly studied (Grunewald and Scheithauer 2010 ). In these situations, upward plant colonization following the chronosequence is expected as a main pattern (Fisher et al. 2019, Losapio et al. 2025 ). Alternatively, as these mountains have poorly vegetated peaks and ridges above the glaciers, downward plant colonization seems like an equally plausible scenario, but was never documented in deglaciated mountains such as the Pyrenees. Describing plant colonization processes in nearly extinct glaciers is key to assess the dynamics of the newly emerging mountain ecosystems in deglaciated areas, helping to understand past processes and generating knowledge for proper future conservation of these unique areas under climate change. The Pyrenees provide a unique opportunity to address this scientific challenge for different reasons: i) they host very small glaciers which are expected to disappear in the following decades ii) the cartography of the glaciers and their dynamics during the last decades is well documented and iii) the flora and vegetation of the Pyrenees is exhaustively described. In this study, we aim to understand how plant colonization takes place after the retreat of the Aneto glacier, located in the Central Pyrenees. Besides a description of the process, we want to test the following hypotheses: i) the plant community composition will differ between deglaciated slopes and never-glaciated nearby slopes, as well as within the deglaciated areas, depending on the ice retreat date, ii) plant diversity will decrease towards more recently deglaciated areas at higher altitudes, and iii) the source of plant colonization should include both lower elevation habitats and high elevation ridges resulting in coexisting upwards and downwards colonization processes. 2. Materials and Methods Study site The study area is located at a north facing slope in the Maladeta massif in the Central Pyrenees (0.65°E, 42.64°N). It is right below the peaks of Maladeta (3312 m a.s.l.) and Aneto (3404 m a.s.l.), the latter being the highest peak in the Pyrenees (Fig. 1 ). The upper part of the slope is occupied by the Aneto glacier. It covered 34.4 ha in 2023 with a maximal length of ~ 500 m between 3000 m a.s.l. and 3140 m a.s.l. (Izagirre et al. 2024 ). The glacier front was down to ~ 2500 m a.s.l. at the end of the LIA, from which it has consistently receded until now. The lower part of the slope is either bare granodiorite, detritic sediment or shallow soil and low vegetation (Vidaller et al. 2025 ). Reconstruction of a chronosequence of the Aneto glacier front position A time series of the front position of the Aneto glacier was created from aerial images, terrestrial photography, UAV imagery and airborne LiDAR and existing datasets (Vidaller et al. 2023 ; Izagirre et al. 2024 ). The front positions were retrieved from satellite images from 1990, 2000 and 2011, and images taken from UAV for the years 2020 and 2023. An aerial ortho-image at a 0.5 m resolution from the American flight program was used to retrieve the front position in 1946 and 1957. The front was retrieved at older dates in 1875 and 1934 from terrestrial photographs of mountaineers (i.e. Fig. S1 ). The position of the highest frontal moraine observed on contemporary ortho-images was assumed to correspond to the LIA maximal extent around 1850 (Vidaller et al.2023). The historical terrestrial photographs were georeferenced by defining control points in the images and in a contemporary aerial image. Recognizable landmarks such as summits, faults, large rocks and vegetation patches were manually identified in archive and contemporary images. This processing was realized in the Monoplotting tool (Wiesmann et al.2012). The contemporary aerial image and the reference Digital Elevation Model (DEM) were provided by the Spanish national mapping agency ( Instituto Geográfico Nacional-IGN ). The aerial image was resampled from its native resolution of 0.25 m to 1 m to ease calculations. The DEM is derived from aerial lidar and has a resolution of 25 m. The reconstruction of the retreat chronosequence of Aneto glacier is shown in Fig. 1 . Vegetation surveys Field campaigns took place in August 2023 (deglaciated areas) and August 2024 (control areas) at comparable phenological stage. Vegetation was studied at nine sites of interest (Fig. 1 ). Taxonomic nomenclature followed Gómez et al. ( 2020 ) as summarized in Appendix 1 (Supplementary material 1). Six of them were distributed along the deglaciation gradient of the Aneto glacier from the LIA (A1 to A6) and were randomly located within each deglaciation belt. As the glacial retreat is strongly associated with the altitude in the study area, an altitudinal control was set including three sites (C1 to C3) in an adjacent area with no evidence of permanent ice formation since the LIA and similar slope angle, bedrock and aspect. These control localities had a paired altitude with the sites A1 to A3. No control sites were selected at higher elevations since above that altitude no evident long-term ice-free areas were identified (Fig. S1 ). The deglaciation year of each plot was estimated using a linear interpolation based on the distances to the previous and next dated fronts as follows (details in Fig. S2 ): $$\:Deglaciation\:Year={Year}_{1}+\left({Year}_{2}-\:{Year}_{1}\right)\:\times\:\:\frac{{d}_{1}}{{{d}_{1}+d}_{2}}$$ …where Year 1 and d 1 correspond to the dated year and distance from the plot to the previous front, and Year 2 and d 2 refer to the next front. At each site, 10 plots of 1 m by 1 m were set to maximize plant diversity estimation in the surroundings, separating them a minimum of 5 meters. A deglaciation year was associated with each site as the median of the deglaciation year of their 10 plots surveyed per site (Table 1 ). Each plot was divided into 25 cells of 0.2 x 0.2 m (Fig. S3), in which the presence of vascular plant species was recorded. Overall abundance of a species in a 1 x 1m plot was estimated as the frequency of presence in the 25 cells (i.e. 1/25 species only present in one cell and 25/25 = 1 if the species was present in all cells). Besides, the proportion of vegetation (including mosses), soil, and rock (including lichens if present) cover was visually evaluated in each cell and averaged for the plot. Analysis of vegetation diversity and composition For each 1x1m plot, the diversity was estimated by means of the species richness (S) and Shannon Index (H’) (Shannon 1948 ). For each site, accumulated species richness (γ diversity) was then calculated. Vegetation composition of each plot was visualized using NMDS and plotting the 95% confidence interval. We first plotted all 90 vegetation plots together and then separately those from the deglaciated area. Calculations were conducted with R-cran vegan package (Oksanen et al. 2025 ). Jaccard similarity matrix comparing all 90 plots was subtracted. To account for the altitudinal preference of plant species in our study system, the Mean Occurrence Altitude (MOA) of each species in our dataset was calculated as its mean altitudinal occurrence in the dataset weighted by its abundance at each site. Species were then ordered according to their MOA values and classified in 100 metres altitudinal bands (from 2600 to 3000 m). To infer the potential origin of the species pool found in our study, we compared the inventories obtained from our sampling plots with the following three vegetation surveys (table S1 ): i) the Aneto peak (Fernández and Herreros 2014 , 2019 , 2022), ii) el Portillón mountain pass (Fernández and Herreros 2014 ) and iii) el Salterillo lake at the upper limit of dominant shrub vegetation below A1 point (see Fig. 1 for the location of the three localities). For all the species reported in the study, we recorded whether they were present in the Aneto , Portillón and Salterillo surveys and produced a MOA histogram colored accordingly. If a species was represented in two surveys, it was half weighted in each survey category. All figures were made with R-cran ggplot2 package (Wickham 2016 ) in R studio 2024.04.2 except Fig. 5 made in Microsoft Excel 2007 (Microsoft corporation). 3. Results Retreat of the Aneto glacier since 1850 The front of the Aneto glacier showed a marked retreat between the dates defining the chronosequence studied. Between 1850 and 2023, the elevation of the glacier front increased by 28 m per decade on average and its length decreased by 85 m per decade, with nearly 80% reduction in 175 years (Fig. S4). The median deglaciation year of sites A1 to A6 was inferred to be 1862, 1915, 1950, 1988, 2005 and 2009 respectively. Therefore the time since deglaciation to sampling varied from 163 years in A1 site to 15 years in A6 site, covering a chronosequence of 150 years (Table 1 ). Plots in A1 showed the highest variability in deglaciation year with a minimum-maximum range of 13 years, while the other points had a range between 1 and 6 years. The standard deviation of the deglaciation years was 3.3 years and 2.1 years for A1 and A2, and was always lower than 1.5 years for the other sampling areas. This shows the good homogeneity of the timing of deglaciation for a given sampling area and clear distinctiveness between survey sites in terms of deglaciation date. Points C1 and C2 were not covered with ice during this period, as they are outside the LIA moraine systems and appear ice free on the oldest available image from 1875 (Fig. S1 ). Point C3 was also likely not covered with ice during this period, but might have been below year-round persistent snowpack in early times as it appeared closer to small moraines in the field and to ice or snow on the 1875 image. Species composition along the ice retreat gradient In total, 65 species were recorded in the deglaciated area (A1-A6) and 98 in the control area (C1-C3), totaling 114 species(Supplementary material 2). Therefore, in the control area the species richness recorded was 50% higher than in the deglaciated area despite sampling half the plots (i.e thirty & sixty plots and three & six sites). The following seven species were recorded in all deglaciated sites: Leucanthemopsis alpina, Linaria alpina, Gnaphalium supinum ( Omalotheca supina (L.) DC.in POWO 2026 ), Oxyria digyna, Poa alpina, Saxifraga moschata and Veronica alpina.Festuca glacialis was the most abundant species in A1 site, Poa alpina in A2 and A3, Cerastium cerastoides in A4 and A5, and Veronica alpina in A6. In the control area, the most common species across all plots were Vaccinium uliginosum, Festuca eskia, Trifolium alpinum and Thymus praecox . However, Carex sempervirens dominated in C1, Vaccinium uliginosum in C2 and Sagina saginoides in C3. Table S2 summarizes the most relevant species in the study at site, plot and cell level. The composition of plant communities varied along the studied sites (Fig. 2 a and S5 ). Plots from the deglaciated and control sites clearly occupy different spaces in Non-metric Multidimensional Scaling (NMDS), indicating that they consistently had a different species composition. Control sites (C1-C3) did not overlap indicating that the vegetation composition of the control sites was different, yet not similar to the nearby deglaciated area. Clearly, C1 site appeared to be the most divergent and C2 and C3 laid in the periphery of the confidence interval inferred for deglaciated plots. The space within the 95% confidence interval was higher at C1 and C2 compared with sites A1 and A2 at the same altitude in the deglaciated area (see Fig. 2 a and 2 b together), a result aligned with the overall higher diversity values found in these sites (see next section). Although the deglaciated plots shared more species and fell closer to each other in the NMDS space, there was a progressive differentiation from one edge to the other of the chronosequence (Fig. 2 b). Plots from the A1 site, an area deglaciated more than 150 years ago, showed very little within site variation in species composition. Moreover, the A1 plots were the ones closer to the C2 control site, whose vegetation was not influenced by permanent ice since the LIA. This indicates that vegetation composition in the A1 site is not yet similar to the nearby control areas after more than 150 years without an ice cover. The differences in species composition between deglaciated and control sites decreased with time since deglaciation (Fig. 2 b). This process was associated with a decrease in within site variation in plant composition, although plant diversity values were higher (see next section). The plant species composition of plots in the C3 site, located near a moraine laid close to some A5 and A6 plots. Table 1 Site information and diversity values reported. Number of plots (N), altitude in meters (Alt.), median deglaciation year (DY), time since deglaciation (t), coordinates,γ, S and H’ diversity and vegetation cover. Site N Alt. (m) DY ± sd t (years) Coord. (Long, Lat) γ S x ± sd H’ x ± sd Veg. cover (%) A1 10 2600 1862 ± 3.3 163 0.65766, 42.65043 42 16,0 ± 3,1 2,4 ± 0,3 46,0 ± 10,2 A2 10 2740 1915 ± 2.1 109 0.65516, 42.64814 29 12,6 ± 3,9 2,2 ± 0,3 24,2 ± 9,8 A3 10 2870 1950 ± 0.6 74 0.65237, 42.64680 28 9,8 ± 3,5 1,8 ± 0,4 15,4 ± 7,4 A4 10 2920 1988 ± 1.5 36 0.65000, 42.64566 22 8,6 ± 2,8 1,8 ± 0,4 16,5 ± 8,0 A5 10 2960 2005 ± 1.5 19 0.64930, 42.64432 22 7,5 ± 2,2 1,7 ± 0,2 10,8 ± 6,3 A6 10 3000 2009 ± 0.5 15 0.64873, 42.64367 18 4,5 ± 2,1 1,2 ± 0,6 6,0 ± 3,6 C1 10 2580 - - 0.65335, 42.65537 72 15,7 ± 4,7 2,4 ± 0,2 64,0 ± 35,0 C2 10 2700 - - 0.65161, 42.65466 51 19,9 ± 5,4 2,6 ± 0,3 54,1 ± 15,8 C3 10 2870 - - 0.64835, 42.65094 31 8,4 ± 3,6 1,7 ± 0,6 15,6 ± 6,8 Plant cover and diversity along the ice retreat gradient Total vegetation cover, species richness (S) and Shannon Index of species diversity (H’) increased steadily with time since deglaciation (Table 1 and Fig. 3 ). The average vegetation cover increased from less than 6% in recently deglaciated localities, to 46% in localities deglaciated about 163 years ago (Fig. 3 a). Species richness ranged between an average of 16 species per plot in the A1 site, deglaciated 163 years ago, to 4.5 species per plot in the A6 site, deglaciated 15 years ago (Fig. 3 b). H’ value also decreased by half from A1 point to A6 (Fig. 3 c). As the time since deglaciation is correlated with the altitude (Fig. S4), we investigated whether the diversity values exhibited a similar pattern between deglaciated and control areas, although species composition highly differed. Interestingly, the control sites, not covered with ice since the LIA, showed a different pattern than the sites located along the deglaciation gradient. Plant cover values in control sites were higher (significantly for C2 and A2 comparisons) and exhibited greater variability between plots of the same site (Fig. 4 a). Remarkably, C1 locality exhibited the highest variability with some plots with nearly 100% cover recorded. Whereas the diversity values decreased constantly along the deglaciation gradient (correlated with the altitude), in control sites the diversity increased despite the altitude between C1 and C2. Concretely the comparison between A2 and C2 gave a significant difference in species richness. Notably, C3 behaved similarly to the A3 point located at the same altitude in the glaciated area for all diversity and cover measures (Fig. 4 ). Finally, the ɣ diversity, the total species at each site, was considerably higher for control sites compared with the deglaciated sites at the same altitude (C1-A1 and C2-A2 in Fig. 4 d). Overall, these results demonstrate that the vegetation structure and diversity are not the same in control and deglaciated areas, despite sharing the local species pool, bedrock, orientation and climate. Evidence of plant colonization pathways Two opposite plant colonization pathways were detected (Fig. 5 ): (i) a bottom-up pathway, characterized by the presence of numerous species from Salterillo in the lower sector of the forefield, with a gradual decline in shared taxa at higher elevations (e.g. Alchemilla alpina , Festuca sp. , Phyteuma hemisphaericum , Vaccinium uliginosum ); and (ii) a top-down pathway, with summit-derived species from Aneto occurring predominantly in the upper elevation belt (~ 3000 m), and including Saxifraga pubescens , Androsace ciliata , Saxifraga oppositifolia and Minuartia sedoides . The proportion of species present in the Aneto summit decreased markedly at lower altitudes. No clear pattern was observed regarding the intermediate Portillón area. 4. Discussion Vegetation colonization following the ice retreat of the Aneto glacier The Aneto glacier is a relict high alpine glacier occurring in a warm temperate mountain range (Vidaller et al. 2023 ), an environmental setting where research has been primarily focused on geomorphological processes after deglaciation, rather than plant colonization dynamics (Heckmann and Morche 2019 ). It is located way above the treeline, restricting the species pool that can colonize deglaciated areas to strictly alpine and nival species, in contrast with the situation found in more septentrional glaciers, where lowland forest and tundra species pools can colonize deglaciated areas (Vetaas 1994 ;Jones and del Moral 2005 ;Burga et al. 2010 ). Overall, this situation contributes to the novelty of our study and provides the opportunity to test whether most general patterns observed in highly glaciated mountain ranges are also found in less glaciated areas like the Pyrenees, or to point out at some particularities associated with the high mountain nature of the Aneto glacier. Our relict alpine study system in Aneto glacier showed a strong correlation between altitude and the glacial retreat, contrasting with most previous similar studies focused in deglaciation glaciers with less altitudinal variation (Vetaas 1994 ; Mathews and Vater 2015; Fickert 2020 ; Bayle et al. 2023 ; Cantera et al. 2024 ; Tanner et al. 2024 ). An altitudinal control was set in a glacier free adjacent area to integrate the effect of altitude in vegetation composition. Although we identified non-glaciated areas near the deglaciated area, it was not possible to survey a complete altitudinal gradient free of ice and we are aware of that limitation imposed by the geomorphology and glacial dynamics (Burga et al. 2004 ; Heckmann and Morche 2019 ). In any case, the plant composition, cover and diversity patterns observed in Aneto mountain suggest that plant colonization following ice retreat is a process highly decoupled from the process of community assembly that are at play in nearby areas that were not glaciated. Vegetation composition in non-glaciated areas, indeed, strongly differed from the vegetation found in deglaciated areas at similar altitudes. The total species richness found in the control area was 50% higher than in the deglaciated area which was investigated with more sampling effort (i.e. thirty plots at three control sites & sixty plots at six deglaciated sites) indicating that the species pool in the deglaciated area is strongly filtered. The control area presented communities widely found at the same altitude in the Aneto-Maladeta massif. C1 and C2 had deeper soils than any other studied locality, confirming long ice free periods that prevented soil erosion by the glacier. Therefore, dominant plants in these plots were grasses (e.g. Festuca eskia ), sedges (e.g. Carex curvula ) and different members of the Ericaceae family (e.g. Vaccinium uliginosum ). These formations resemble tundra communities and are characterized by deep soils and long lived perennial grasses and shrubs (Chapin et al. 1992 ; Shepelev et al. 2025 ), which is a widespread vegetation facies at similar altitudes in central siliceous Pyrenees (Carrillo, 1984 ). Along the deglaciated area, both species composition and their frequency differed, with pioneers such as Leucanthemompisis alpina, Armeria alpina, Sagina saginoides or Veronica alpin a prevalent, including taxa that were not recorded in control areas (e.g. Pritzelago alpina or Linaria alpina ). Interestingly, most species found in our inventories in the deglaciated area were also found in early successional stages in similar studies in the Alps or the arctic, such as Saxifraga species, Arabis alpina , Poa alpina or Oxyria dygina (Burga et al. 2010 ; Eichel 2019 ). This observation converges with the fact that 75% and 33% of the Pyrenean alpine flora is present in the Alps and Scandinavia, respectively (Gómez et al. 2020 ). Plant diversity estimations also showed clear differences between deglaciated and non-glaciated areas. Plant cover and diversity (S and H’) showed a progressive decline along the altitudinal gradient in the deglaciated slope (inversely correlated with time since deglaciation), contrasting with the unimodal distribution found in the non-glaciated area. Whereas the increase in diversity and plant cover is a common pattern found in primary succession following glacier retreat (Tapucci et al. 2015; Cantera et al. 2024 , Tanner et al. 2024 ; Ficetola et al. 2025), a unimodal distribution of diversity with altitude is commonly found as a response to altitudinal gradients (Mark et al. 2000 ; Fernández-Calzado et al. 2013 ; Sun et al. 2020 ). Accordingly, the diversity patterns at small spatial scales are highly dependent on topological and microclimatic conditions, rather than colonization dynamics (Rydgren et al. 2014 ; Opedal et al. 2014). In our control, C2 represented an area more heterogeneous than C1, hosting more diversity. In areas close to the limits of the glacier, as in C3, the vegetation suffered indirectly in different ways from the effect of having a big glacier nearby in the past. C3 was located in a landscape that combined lateral moraines and a scree originating from the erosion of nearby cliffs, and therefore did not fit an ideal control expectation. Consequently, vegetation composition in C3 differed from C1 and C2 and had lower cover and plant diversity values, as expected in less stable substrates (Burga et al. 2004 ), and resembled the deglaciated plots hosting more pioneer plants. For all the above, and despite the methodological limitations, our data provide strong evidence that the processes determining the composition and structure of vegetation differ between nearby deglaciated and non-deglaciated areas in Aneto mountain, and support the notion that the differences in vegetation found along the deglaciation chronosequence resulted mainly from primary succession and not altitudinal constraints. As expected after a glacier retreat, and contrasting with the control area, the results found in the deglaciation gradient evidenced an ongoing colonization process aligned with previous studies in other glaciated areas of the world (Jones et al 2003; Ficetola et al. 2024 ; Losapio et al. 2025 ). Vegetation cover and diversity measures provided evidence that plant communities gained species and structure through time since ice retreat (Bayle et al. 2023 ; Ficetola et al. 2024 ). The Aneto glacier retreat left an extensive granite surface eroded with very few cracks and spots favorable for plant establishment after the ice retreat (Fig. S7). With time, in certain areas where water and sediments accumulated, the soil started to develop allowing plant colonization. These dynamics also found in other glaciers explain why long deglaciated plots exhibited more plant cover and species diversity than recently deglaciated ones (Eichel, 2019 ). It is expected that, on a long term, the vegetation of deglaciated areas will evolve to grass and shrub dominated communities more similar to C1 and C2, as plant dispersal is feasible and altitude, slope and orientation are similar. Interestingly, the plots located in areas deglaciated more than a century and a half ago retained different plant species to non-glaciated areas, indicating that homogenization of vegetation between control and deglaciated areas may require considerable more time. This contrasts with general findings in more conventional glaciers which estimated a century as the minimum time needed until surrounding mature communities completely colonized deglaciated areas (Burga et al. 2010 ; Ficetola et al. 2021 ). Moreover, a common pattern described in the literature is that plant diversity tends to diminish once plant communities reach maturity (Tampucci et al. 2015 ; Glausen and Tanner. 2019; Tanner et al. 2024 ), and replacement prevails over the addition of species (Cantera et al. 2024 ). These situations were not found in our system yet, reinforcing the idea that the colonization process that started after LIA is still ongoing. This delay in colonization is likely explained by the slowdown of biological processes at high altitude (Körner 2003 ), or by the snow legacy (Choler et al. 2025 ), and may need up to four centuries (Cantera et al. 2024 ). Our data suggest that the development of plant communities in these periglacial areas is largely dependent on ice-free time, expected to be associated with soil development (Ficetola et al. 2021 and 2014, Losapio et al. 2015). This contrasts with previous findings in our study area showing a weak pattern in soil structure along the same deglaciation gradient (Vidaller et al. 2025 ), but this lack of correlation was also found by Wei et al. ( 2021 ). This fact clearly indicates the need of further studies to couple soil and vegetation processes, because their dynamics do not respond necessarily to the same factors and they have to be studied simultaneously under the same design (Wei et al. 2021 , Ficetola et al. 2024 ). First of all, sediments are transported by ice, so the glacier retreat does not imply a time 0 for soil formation, as it does for plant colonization; soil can be developed already under the ice (Heckmann and Morche, 2019 ). Besides, primary soil development depends on the equilibrium between sedimentation and disturbances (Ficket and Gruninger, 2018) and in proper spots, soil will develop and structure with time (Wei et al. 2021 ). Finally, plants themselves are the most important agents to develop proper organic soils on top of the initial mineral soils (Eichel 2019 ) and its presence is positively linked with other components of the ecosystem (Ficetola et al. 2024 ). As the plant colonization process in the deglaciated gradient is not completed, we consider that the match between soil development in bare and vegetated areas is expected to be uncoupled. Drivers of vegetation colonization in the deglaciated areas of the Aneto glacier Plant colonization in deglaciated areas is expected to occur mainly from communities surrounding the glacier area. Most successional studies along glacial retreat chronosequences have been conducted in tongs of large glaciers (Vetaas 1994 ; Jones and de Moral, 2005; Glaussen and Tanner, 2019; Nota et al. 2025 ), where the main colonization sources may be located not only below the glacier, but also in the surrounding slopes at higher altitudes also hosting similar plant communities. Opposite to that situation, the Aneto glacier is restricted to the upper part of the highest mountain in the Pyrenees. This limits the main potential colonization sources in the study system to two, one below the glacier and another one above it, including the ridges and summits. Concretely, the LIA maximum extent of the glacier is now surrounded by alpine grasslands of Festuca eskia and Nardus stricta , combined with heath shrubs which dominate at altitudinal ranges between 2200 and 2500 meters, similar to the lower control areas. However, the Aneto glacier is now restricted to the nival belt at altitudes above 3000 meters, so the upper front of the glacier is surrounded by rocky ridges where very few plants grow. Still, among them there are several endemic (i.e Saxifraga iratiana , Androsace ciliata ) or boreoalpine taxa (i.e Ranunculus glacialis , Arabis alpina ), which have their growing optimum at this altitude. They are postulated to be cold adapted plants, which find refuge in the coldest part of the mountain, and are at risk of local extinction as the vegetation of the mountain tops increases its richness (Steinbauer et al. 2018 ). An interesting finding of this study is that colonization following ice retreat in the Aneto glacier took place in two directions: upward and downward. In the upper part of the deglaciated area, there were species also found at the top of the Aneto mountain, which are representative of the vegetation found along the Aneto-Maladeta ridge above the glacier. These species decreased drastically at lower altitudes. We interpret this as an effect of gravity directly or, indirectly, through water flows that may transport the seeds of these high alpine plants from the ridges. In parallel, the vegetation found in the lower part of the deglaciated area, even if different in overall plant composition from the non-glaciated surrounding areas, shared more than half of the species with the nearby source communities, here represented with vegetation surveys conducted in the surroundings of Salterillo lake. The percentage of species shared with Salterillo decreased towards the upper part of the deglaciated part of the glacier. It is remarkable that although altitude is not strongly determining the colonization and diversity patterns along the chronosequence it plays an important role determining the species source for the colonization. To the best of our knowledge, this is the first evidence of an altitude-structured plant colonization source following glacier retreat, and may be explained by the high altitude and relict nature of the Aneto glacier, not shared with most previous studies. This finding also highlights the ecological relevance of in situ survival of plants in nunataks, which have long been discussed in the Pyrenees (Segarra-Moragues 2007; Carnicero et al. 2022 ). Finally, from a conservation perspective, our results provide strong evidence that in high alpine nearly extinct glaciers, the colonization of newly opened ice free areas may serve as an opportunity for rare and climatically threatened alpine species to extend their potential range. In five to ten years, a revisit of the Aneto area should be undertaken to document the future evolution of plant colonization in the area. To this end, the GPS coordinates and pictures (lateral and zenithal) of each plot were taken to ensure reproducibility of the inventories in the future. 5. Conclusion The Aneto glacier represents a unique study system to understand the colonization processes not only along a glacier retreat chronosequence at high elevation and steep slopes, but also in a situation where glacier disappearance is expected in a few years period. The vegetation along the deglaciation gradient in the Aneto glacier follows an expected pattern of increase of cover and diversity since the LIA, with a different composition from the non-glaciated surrounding areas. After more than a century and a half, these differences are still notorious, and the successional dynamics seem to be ongoing. The main species source for colonization of the deglaciated area in Aneto is the vegetation from lower altitudes, but colonization of the higher part of the deglaciation gradient is strongly dominated by plants growing in the tops and ridges of the massif, providing and evidence of a complementary downwards colonization process. Similar patterns of colonization to those described here can be expected in other glaciers of the Pyrenees. Besides, differences in the colonization pattern can be expected with different topography, bedrocks, climate and native vegetation. Studying in a similar way other periglacial areas of the Pyrenees would enable to evaluate the generality of the patterns highlighted here and the potential for alpine plant species conservation in the context of climate change. Declarations Author Contribution The study was designed by PT, CSB, JILM, JR, SP with the assistance of IV, OF, SL and PR. Field work was conducted by PT, CDB, NCR, FRH, AA, ALV, OF. The analyses and figure production were conducted by NCR, AA, CDB and PT. Writing and edition of the manuscript was led by PT and CDB. The review and edition of the manuscript has been accomplished by all authors who gave final approval for publication. Acknowledgement This study was supported by the POCTEFA program from the EU through FLORAPYR 3D (EFA064/01) project, the Spanish Ministry of Science and Innovation through MARGISNOW (PID2021-124220OB-100) project and postdoctoral grant (FJC2021‐047268‐I)), the Leonardo program of the BBVA research foundation through MeltingIce project and the French Space Agency (Centre National d'Etudes Spatiales, CNES) through a postdoctoral fellowship. Jaca Herbarium has allocated its own resources to the study. We thank the authorities of the Posets-Maladata Natural Park for the support to our study. We also thank Idoia Biurrun from the UPV-EHU for her comments and suggestions. Data Availability The dataset generated and analyzed during the current study is available from the corresponding author upon reasonable request. References Anthelme F, Carrasquer I, Ceballos JL, Peyre G (2022) \ \ Novel\ plant\ communities\ after\ glacial\ retreat\ in\ Colombia:\ \(many\)\ losses\ and\ \(few\)\ gains\.\ https://www\.zotero\.org/google\-docs/\?06zzd5 \ \h Bayle A, Carlson BZ, Zimmer A, Vallée S, Rabatel A, Cremonese E et al (2023) Local environmental context drives heterogeneity of early succession dynamics in alpine glacier forefields. Biogeosciences20 (8):1649–1669. https://doi.org/10.5194/bg-20-1649-2023 Bosson JB, Huss M, Cauvy-Fraunié S, Clément JC, Costes G, Fischer M et al (2023) Future emergence of new ecosystems caused by glacial retreat. Nature. 620(7974):562–569. https://doi.org/10.1038/s41586-023-06302-2 Burga CA, Frauenfelder R, Ruffet J, Hoelzle M, Kääb A (2004) Vegetation on Alpine rock glacier surfaces: a contribution to abundance and dynamics on extreme plant habitats. Flora 199(6):505–515. https://doi.org/10.1078/0367-2530-00179 Burga CA, Krüsi B, Egli M, Wernli M, Elsener S, Ziefle M, Fischer T, Mavris C (2010) Plant succession and soil development on the foreland of the Morteratsch glacier (Pontresina, Switzerland): Straight forward or chaotic? Flora 205(9):561–576. https://doi.org/10.1016/j.flora.2009.10.001 Cantera I, Carteron A, Guerrieri A et al (2024) The importance of species addition ‘versus’ replacement varies over succession in plant communities after glacier retreat. Nat Plants 10:256–267. https://doi.org/10.1038/s41477-023-01609-4 Carnicero P, Wessely J, Moser D, Font X, Dullinger S, Schönswetter P (2022) Postglacial range expansion of high-elevation plants is restricted by dispersal ability and habitat specialization. J Biogeogr 49:1739–1752. https://doi.org/10.1111/jbi.14390 Carrillo A (1984) La Flora i la Vegetacio de l'Alta muntanya de les Valls d'Espot i de Boi (Pirineus Centrals). PhD. Universitat de Barcelona Chapin FS, Jefferies RL, Reynolds JF, Shaver GR, Svoboda J (1992) Arctic Ecosystems in a Changing Climate. Academic, Inc.San Diego, CA Choler P, Bonfanti N, Reverdy A et al (2025) Legacy of snow cover on alpine landscapes. Commun Earth Environ 6:758. https://doi.org/10.1038/s43247-025-02702-6 Dentant C, Carlson BZ, Bartalucci N, Bayle A, Lavergne S (2024) Anthropocene trajectories of high alpine vegetation on Mont-Blanc nunataks. Bot Lett 171(1):65–79. https://doi.org/10.1080/23818107.2023.2231503 Dussaillant I, Hugonnet R, Huss M, Berthier E, Bannwart J, Paul F, Zemp M (2025) Annual mass change of the world’s glaciers from 1976 to 2024 by temporal downscaling of satellite data with in situ observations. Earth Syst Sci Data 17(5):1977–2006. https://doi.org/10.5194/essd-17-1977-2025 Eichel J (2019) Vegetation succession and biogeomorphic interactions in glacier forelads. In: Heckmann T, Morche D (eds) Landform and sediment dynamics in recently deglaciated alpine landscapes, vol 327. Springer, Switzerland, p 350 Fernández O, Herreros MJ (2014) Seguimiento de la diversidad florística en las cumbres del Pirineo aragonés. Instituto de Estudios Altoaragoneses Fernández O, Herreros MJ (2019) 2022) Seguimiento de la diversidad florística en las cumbres del Parque Natural Posets-Maladeta como indicador de cambios. Gobierno de Aragón Fernández-Calzado R, Ghosn D, Gottfried M, Kazakis G, Molero Mesa J, Pauli H, Merzouki A (2013) Modelos de endemicidad a lo largo de un gradiente altitudinal en Sierra Nevada (España) y Lefka Ori (Creta, Grecia). Pirineos 168:7–24. https://doi.org/10.3989/Pirineos.2013.168001 Ficetola GF, Marta S, Guerrieri A, Gobbi M, Ambrosini R, Fontaneto D, Zerboni A, Poulenard J, Caccianiga M, Thuiller W (2021) Dynamics of Ecological Communities Following Current Retreat of Glaciers. Annu Rev Ecol Evol Syst 52:405–426. https://doi.org/10.1146/annurev-ecolsys-010521040017 Ficetola GF, Marta S, Guerrieri A, Cantera I, Bonin A, Cauvy-Fraunié S et al (2024) The development of terrestrial ecosystems emerging after glacier retreat. Nature632 (8024):336–342. https://doi.org/10.1038/s41586-024-07778-2 Fickert T, Grüninger F (2018) High-speed colonization of bare ground—Permanent plot studies on primary succession of plants in recently deglaciated glacier forelands. Land Degrad Dev 29:2668–2680. https://doi.org/10.1002/ldr.3063 Fickert T (2020) Common patterns and diverging trajectories in primary succession of plants in eastern alpine glacier forelands. Diversity 12:191. https://doi.org/10.3390/d12050191 Glausen TG, Tanner LH (2019) Successional trends and processes on a glacial foreland in Southern Iceland studied by repeated species counts. Ecol Process 8:11. https://doi.org/10.1186/s13717-019-0165-9 Grunewald K, Scheithauer J (2010) Europe’s southernmost glaciers: response and adaptation to climate change. J Glaciol 56(195):129–142. 10.3189/002214310791190947 Gómez D, Ferrández JV, Bernal M, Campo A, Retamero JRL, Ezquerra V (2020) Plantas de las cumbres del Pirineo. PRAMES. Zaragoza Heckmann T, Morche D (2019) Landform and sediment dynamics in recently deglaciated alpine landscapes. Springer, Switzerland Hewitt G (1999) Post-glacial re-colonization of European biota. Biol J Linn Soc 68(1–2):87–112. https://doi.org/10.1111/j.1095-8312.1999.tb01160.x Hock R, Rasul G, Adler C, Cáceres B, Gruber S, Hirabayashi Y, Jackson M, Kääb A, Kang S, Kutuzov S, Milner Al, Molau U, Morin S, Orlove B, Steltzer H (2019) High Mountain Areas. In: Pörtner HO, Roberts DC, Masson-Delmotte V, Zhai P, Tignor M, Poloczanska E, Mintenbeck K, Alegría A, Nicolai M, Okem A, Petzold J, Rama B, Weyer NM (eds) IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp 131–202. https://doi.org/10.1017/9781009157964.004 Izagirre E, Revuelto J, Vidaller I, Deschamps-Berger C, Rojas-Heredia F, Rico I et al (2024) Pyrenean glaciers are disappearing fast: state of the glaciers after the extreme mass losses in 2022 and 2023. Reg Environ Change 24:172. .https://doi.org/10.1007/s10113-024-02333-1 Jones C, del Moral R (2005) Patterns of Primary Succession on the Foreland of Coleman Glacier, Washington, USA. (2005). Plant Ecol. 180:105–116. https://doi.org/10.1007/s11258-005-2843-1 Kadereit JW (2024) The uneven distribution of refugial endemics across the European Alps suggests a threefold role of climate in speciation of refugial populations. Alp Bot 134:29–50. https://doi.org/10.1007/s00035-024-00306-y Körner C (2003) Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystems (2nd edition). Springer, Berlin Leonelli G, Masseroli A, Trombino L, Golzio A, Bonetti A, Maggi V et al (2024) Development of the critical zone environment in the highly dynamic landscape of the Forni Glacier forefield: Winds, tree vegetation, pedogenesis and surface waters after glacier retreat. Earth Surf Process Landf 49(14):4587–4609. https://doi.org/10.1002/esp.5983 López-Moreno JI, Revuelto J, Izagirre E, Alonso-González E, Vidaller I, Bonsoms J (2025) No hope for Pyrenean glaciers. Ann Glaciol 66:e17. https://doi.org/10.1017/aog.2025.10015 Losapio G, Lee JR, Fraser CI, Gillespie MAK, Kerr NR, Zawierucha K, Hamilton TL et al (2025) Impacts of deglaciation on biodiversity and ecosystem function. Nat Rev Biodivers 1(6):371–385. https://doi.org/10.1038/s44358-025-00049-6 Mandel JR, Dikow RB, Siniscalchi CM, Thapa R, Watson LE, Funk VA (2019) A fully resolved backbone phylogeny reveals numerous dispersals and explosive diversifications throughout the history of Asteraceae. Proc Natl Acad Sci USA 9(28):14083–14088. 10.1073/pnas.1903871116 Mark AF, Dickinson KJM, Hofstede RGM (2000) Alpine Vegetation, Plant Distribution, Life Forms, and Environments in a Perhumid New Zealand Region: Oceanic and Tropical High Mountain Affinities. Arct Antarct Alp Res 32(3):240–254. https://doi.org/10.1080/15230430.2000.12003361 Nogues-Bravo D, Rodríguez-Sánchez F, Orsini L, de Boer E, Jansson R, Morlon H, Fordham DA, Jackson ST (2018) Cracking the code of biodiversity responses to past climate change. Trends Ecol Evol 33(10):765–776. https://doi.org/10.1016/j.tree.2018.07.005 Nota G, Enri SR, Lonati M, Mainetti A (2025) Faster than expected: 5-year re-surveys reveal accelerating plant colonization in two proglacial forelands of the Gran Paradiso National Park (NW Italian Alps). Bot J Linn Soc 207(3):266–278. https://doi.org/10.1093/botlinnean/boae043 Opedal ØH, Armbruster WS, Graae BJ (2015) Linking small-scale topography with microclimate, plant species diversity and intra-specific trait variation in an alpine landscape. Plant Ecol Divers 8(3):305–315. https://doi.org/10.1080/17550874.2014.987330 Oksanen J, Simpson GL, Blanchet FG, Kindt R, Legendre P, Minchin PR et al (2025) vegan: Community Ecology Package. R package version X.Y-Z. https://CRAN.R-project.org/package=vegan Parisod C (2008) Postglacial recolonisation of plants in the western Alps of Switzerland. Bot Helv 118:1–12. https://doi.org/10.1007/s00035-008-0825-3 RStudio: Integrated Development Environment for R.Posit Software, PBC, Posit team, Boston (2025) MA. URL http://www.posit.co/ POWO (2026) Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. https://powo.science.kew.org/ Retrieved 05 January 2026 Rydgren K, Halvorsen R, Töpper JP, Njøs JM (2014) Glacier foreland succession and the fading effect of terrain age. J Veg Sci 25:1367–1380. https://doi.org/10.1111/jvs.12184 Schuster L, Maussion F, Rounce D, Ultee L, Schmitt P, Lacroix F, Frölicher TL, Schleussner CF (2025) Irreversible glacier change and trough water for centuries after overshooting 1.5°C. Nat Clim Chang 15:634–641. https://doi.org/10.1038/s41558-025-02318-w Shannon CE (1948) A mathematical theory of communication. Bell Syst Tech J 27(3):379–423. https://doi.org/10.1002/j.1538-7305.1948.tb01338.x Shepelev AG, Efimova AP, Maximov TC (2025) Carbon Stocks and Microbial Activity in the Low Arctic Tundra of the Yana–Indigirka Lowland, Russia. Land 14(9):1839. https://doi.org/10.3390/land14091839 Segarra-Moragues JG, Palop-Esteban M, González-Candelas F, Catalán P (2007) Nunatak survival vs. tabula rasa in the Central Pyrenees: a study on the endemic plant species Borderea pyrenaica (Dioscoreaceae). J Biogeogr 34:1893–1906. https://doi.org/10.1111/j.1365-2699.2007.01740.x Steinbauer MJ, Grytnes JA, Jurasinski G et al (2018) Accelerated increase in plant species richness on mountain summits is linked to warming. Nature 556:231–234. https://doi.org/10.1038/s41586-018-0005-6 Sun L, Luo J, Qian L, Deng T, Sun H (2020) The relationship between elevation and seed-plant species richness in the Mt. Namjagbarwa region (Eastern Himalayas) and its underlying determinants. Glob Ecol Conserv 23e01053. https://doi.org/10.1016/j.gecco.2020.e01053 The GlaMBIE Team, Zemp M, Jakob L, Dussaillant I, Nussbaumer SU, Gourmelen N et al (2025) Community estimate of global glacier mass changes from 2000 to 2023. Nature 639(8054):382–388. https://doi.org/10.1038/s41586-024-08545-z Tanner L, Kikukawa G, Weits K (2024) The temporal and spatial dynamics of succession in a glacial foreland in southern Iceland: the effects of landscape heterogeneity. Land 13(7):1055. https://doi.org/10.3390/land13071055 Tampucci D, Gobbi M, Boracchi P, Cabrini E, Compostella C, Mangili F, Marano G, Pantini P, Caccianiga M (2015) Plant and arthropod colonisation of a glacier foreland in a peripheral mountain range. Biodiversity 16(4):213–223. http://doi.org/10.1080/14888386.2015.1117990 Tovar C, Melcher I, Kusumoto B et al (2020) Plant dispersal strategies of high tropical alpine communities across the Andes. J Ecol 108:1910–1922. https://doi.org/10.1111/1365-2745.13416 Velasquez Casallas LM, Khelidj N, Morán-Ordóñez A, Losapio G (2025) Global impacts of glacier retreat on ecosystem services provided by soil and vegetation in mountain Regions: A literature review. Ecosyst Serv 73:101730. https://doi.org/10.1016/j.ecoser.2025.101730 Vetaas OR (1994) Primary Succession of Plant Assemblages on a Glacier Foreland–Bødalsbreen, Southern Norway. J Biogeogr 21(3):297–308. https://doi.org/10.2307/2845531 Vidaller I, Izagirre E, Del Rio LM, Alonso-González E, Rojas-Heredia F, Serrano E et al (2023) The Aneto glacier’s (Central Pyrenees) evolution from 1981 to 2022: ice loss observed from historic aerial image photogrammetry and remote sensing techniques, vol 17. Cryosphere, pp 3177–3192. 8 https://doi.org/10.5194/tc-17-3177-2023 Vidaller I, Otero XL, Igual JM, Nobrega GN, Ferreira TO, Moreno A, López-Moreno JI (2025) Incipient soils: New habitats in proglacial areas of the Maladeta massif (Central Pyrenees). Sci Total Environ 967:178740. https://doi.org/10.1016/j.scitotenv.2025.178740 Wei T, Shangguan D, Yi S, Ding Y (2021) Characteristics and controls of vegetation and diversity changes monitored with an unmanned aerial vehicle (UAV) in the foreland of the Urumqi Glacier 1, Tianshan, China. Sci Total Environ 771. https://doi.org/10.1016/j.scitotenv.2021.145433 Wickham H (2016) ggplot2: Elegant Graphics for Data Analysis. Springer-, New York. https://ggplot2.tidyverse.org Wiesmann S, Steiner L, Pozzi M, Bozzini C, Bauder A, Hurni L (2012) Reconstructing Historic Glacier States Based on Terrestrial Oblique Photographs. Proceedings - AutoCarto 2012 - Columbus, Ohio, USA Whittaker RH (1978) Classification of vegetation. Dr W. Junk, The Hague, NL Wootton LM, Boucher FC, Renaud J, Valla PG, Midolo G, Lososová Z, Thuiller W, Lavergne S (2025) The Limited Legacy of Post-Glacial Recolonization in the Floristic Patterns of the European Alps. Syst Bot 50(1):83–98. https://doi.org/10.1600/036364425X17466502618876 Additional Declarations No competing interests reported. Supplementary Files Tejeroetal2026Supplementarymaterial1.docx Tejeroetal2026Supplementarymaterial2.xlsx Supplementaryinformation.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8663348","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":580439266,"identity":"cc8f2c0e-c097-4284-bf57-836a16e77a48","order_by":0,"name":"Pablo Tejero","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5UlEQVRIiWNgGAWjYFACxjYwxc8M4fIQ1sEG1SLZTLwWIAQBgwPEOstcvrntwc899+SNj/MefMBQUyfD38B8+AM+LZZtjO2GPc+KDbcd5ks2YDh2mEfiAFuaBD4tBscY2yR4DiQwbjvMYybB2HCAx4CBxwyvw0BaJP8cSLDf3Mxj/oOxoQ6ohf8zXoeBtEgDbUncwAw0nLGBGWQLA16HWbYlthvLHEhIngH0i0QCyC+H2czwajFnPv7s4ZsDCbb9/WcPfvhQU2fP3978GL/DEExgJCaAaGZ86jG0jIJRMApGwSjABgCYvkJjOlfmAQAAAABJRU5ErkJggg==","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":true,"prefix":"","firstName":"Pablo","middleName":"","lastName":"Tejero","suffix":""},{"id":580439267,"identity":"7b926709-86d2-421d-adea-30ad79d81b09","order_by":1,"name":"Cesar Deschamps-Berger","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Cesar","middleName":"","lastName":"Deschamps-Berger","suffix":""},{"id":580439268,"identity":"db19496b-0588-4562-a119-ddb0b671b945","order_by":2,"name":"Nahia Carretero-Roque","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Nahia","middleName":"","lastName":"Carretero-Roque","suffix":""},{"id":580439269,"identity":"4491992e-320c-49da-b0e4-803d29f025a9","order_by":3,"name":"Juan Ignacio Lopez-Moreno","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Juan","middleName":"Ignacio","lastName":"Lopez-Moreno","suffix":""},{"id":580439270,"identity":"9652feb0-4d2c-4109-b830-bbe12246e173","order_by":4,"name":"Jesús Revuelto","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Jesús","middleName":"","lastName":"Revuelto","suffix":""},{"id":580439271,"identity":"4bb8baf3-262f-49ce-b71b-5e99eb4b8d8d","order_by":5,"name":"Francisco Rojas-Heredia","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Francisco","middleName":"","lastName":"Rojas-Heredia","suffix":""},{"id":580439274,"identity":"eca1e0f2-0875-4b7c-8f88-aa6e980ea0c8","order_by":6,"name":"Ixeia Vidaller","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Ixeia","middleName":"","lastName":"Vidaller","suffix":""},{"id":580439276,"identity":"ce7e465a-940d-4335-86b2-7d00092535e3","order_by":7,"name":"Pierre René","email":"","orcid":"","institution":"Association Moraine","correspondingAuthor":false,"prefix":"","firstName":"Pierre","middleName":"","lastName":"René","suffix":""},{"id":580439277,"identity":"4f887427-2007-4cf2-8556-ff41882281ac","order_by":8,"name":"Sébastien Lavergne","email":"","orcid":"","institution":"Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, LECA, Laboratoire d’Écologie Alpine","correspondingAuthor":false,"prefix":"","firstName":"Sébastien","middleName":"","lastName":"Lavergne","suffix":""},{"id":580439280,"identity":"a069bb40-2fe0-4e9f-9f5a-08a050cbe7b8","order_by":9,"name":"Aina Álvarez","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Aina","middleName":"","lastName":"Álvarez","suffix":""},{"id":580439282,"identity":"934a96e1-2eec-4eb4-a461-e17c375d41a9","order_by":10,"name":"Alba López-Varela","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Alba","middleName":"","lastName":"López-Varela","suffix":""},{"id":580439286,"identity":"5ce0f83e-cd58-4cbe-bb0e-4e78af644e1d","order_by":11,"name":"Olatz Fernández","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Olatz","middleName":"","lastName":"Fernández","suffix":""},{"id":580439287,"identity":"03d5d072-375d-4555-93d0-b28fd985a2c0","order_by":12,"name":"Sara Palacio","email":"","orcid":"","institution":"Instituto Pirenaico de Ecología (CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Sara","middleName":"","lastName":"Palacio","suffix":""}],"badges":[],"createdAt":"2026-01-21 20:38:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8663348/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8663348/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101258064,"identity":"39646037-9346-48de-ac9c-358147a31d56","added_by":"auto","created_at":"2026-01-27 19:27:19","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1980367,"visible":true,"origin":"","legend":"\u003cp\u003eStudy sites and plots along the Aneto ice retreat gradient (A1-A6) and non glaciated nearby control area (C1-C3). Glacier front datation is represented with colored lines. The dashed line represents the moraine at the Little Ice Age.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/d0d9acf0c94aa7a32daa819e.jpeg"},{"id":101258063,"identity":"9e12e1c4-4054-423d-ac74-7a79656a6a34","added_by":"auto","created_at":"2026-01-27 19:27:19","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":203547,"visible":true,"origin":"","legend":"\u003cp\u003eNon-metric Multidimensional Scaling (NMDS) showing differences in plant composition of plots. Ellipses show the confidence interval (95%).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/a3a3af61874a986fe30b0e9c.jpeg"},{"id":101297440,"identity":"6b3b3c9d-5f67-41a0-a027-82f3af4f2b55","added_by":"auto","created_at":"2026-01-28 09:27:11","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":92073,"visible":true,"origin":"","legend":"\u003cp\u003eBox plots showing a) vegetation cover (%), b) species richness (S) and c) Shannon Index (H’) against the deglaciation year for the sites in the glaciated area (A1-A6). The median year of deglaciation is shown on top. Significance between sites for each variable is summarized in Fig. S6.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/c1addebf22bb152296342ca1.jpeg"},{"id":101258068,"identity":"c79edd40-d913-4c05-8722-bbc536cfa848","added_by":"auto","created_at":"2026-01-27 19:27:19","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":137369,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of plant diversity and cover between deglaciated and control sites along a comparable altitudinal gradient. a) Pant cover, b) Species Richness, c) Shannon diversity and d) ɣ diversity. Ɣ diversity does not have variation because represents a unique value per site.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/fee98e454c56fdf0752ef46e.jpeg"},{"id":101258067,"identity":"f56ba4bd-a51d-46f5-9259-d20471217efd","added_by":"auto","created_at":"2026-01-27 19:27:19","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":25779,"visible":true,"origin":"","legend":"\u003cp\u003eMOA histogram showing the concurrence of species found in the present study and surveys from \u003cem\u003eAneto\u003c/em\u003e summit, \u003cem\u003eSalterillo\u003c/em\u003e and an intermediate altitudinal point in \u003cem\u003ePortillon\u003c/em\u003e. Y axis classifies plants attending to their abundance-weighted Mean Occurrence Altitude (MOA) in 100 meter bands. X axis shows the number of species assigned to each altitudinal band. Species not found in previous surveys are classified as indeterminate.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/c15cd7aa86019b0571f5d032.jpeg"},{"id":103929550,"identity":"abf3a8cc-e1f6-4959-b3c2-29a1c5eceb4f","added_by":"auto","created_at":"2026-03-04 16:11:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3316556,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/eb73d3a1-140a-4355-b407-0021f1f8ec8b.pdf"},{"id":101258066,"identity":"17062082-d8a2-410e-81ff-0019f0c76194","added_by":"auto","created_at":"2026-01-27 19:27:19","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":5199328,"visible":true,"origin":"","legend":"","description":"","filename":"Tejeroetal2026Supplementarymaterial1.docx","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/4c77b9b564d731f4a0930230.docx"},{"id":101258069,"identity":"f9bcf284-870d-478e-8b74-5a8eb3b469fd","added_by":"auto","created_at":"2026-01-27 19:27:19","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":51802,"visible":true,"origin":"","legend":"","description":"","filename":"Tejeroetal2026Supplementarymaterial2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/9ec7c963a01f9b320bdc3b59.xlsx"},{"id":101258071,"identity":"c86fc8ca-56f0-4196-bef6-d1c91a7a88cb","added_by":"auto","created_at":"2026-01-27 19:27:20","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":16743,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8663348/v1/3d445dcf4b4bb0f5ec4d5a9f.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Upward and downward colonization of vegetation following the retreat of the Aneto glacier, since the Little Ice Age","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe global glacier surface has been shrinking throughout the Holocene, but human-driven climate change in recent decades has greatly accelerated this decline (Hock et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Losapio et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The increase in temperatures and the related decrease in snow precipitation have led to a negative mass balance of most glaciers across the planet (Dussaillant et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; The GlaMBIE Team et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Consequently, continental ice mass is decreasing with the associated loss of water reservoirs, which may have a strong influence on multiple ecosystem services and an impact on the economical and social development of human societies (Schuster et al. 2024).\u003c/p\u003e \u003cp\u003eIn this context of massive glacier retreat worldwide, temperate mountain ranges are the most prone to lose their permanent ice cover (Dussaillant et al.2025). The disappearance of glaciers alters the water regime of tributary drainages, which may lead to cascading ecological changes. In the alpine and nival vegetation belt (\u003cem\u003esensu\u003c/em\u003e Withttaker, 1978), new ice-free surfaces become available for life colonization and the establishment of novel alpine communities, buffering the overall threat to these ecosystems under current climate warming (Bosson et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Ficetola et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This ecological context of primary ecological succession, where vegetation colonizes a recently uncovered barren rocky landscape, provides a unique setting to study the fundamental processes of vegetation development (Bosson et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe Pyrenees are a great example of temperate but still glaciated mountains. In 2023 there were fifteen small relict glaciers restricted to the upper north faces of the highest massifs (Izagirre et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Monitoring and modeling indicate accelerated shrinkage of all ice-covered area with an estimated complete disappearance of Pyrenean glaciers by 2034 (L\u0026oacute;pez-Moreno et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The Aneto glacier is of particular interest because it is the largest glacier in the Pyrenees and has experienced a dramatic surface decrease since the end of the Little Ice Age (LIA, circa 1850), opening hectares of ice-free surfaces for pioneering organisms to colonize. The Aneto-Maladeta massif has lost 88% (6.22 km\u0026sup2;) of its glaciated area between 1850 and 2021 (Vidaller et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), which provided barren rocky surfaces available for plant colonization at different dates along the chronosequence of glacier retreat.\u003c/p\u003e \u003cp\u003eThere is solid evidence that during Pleistocene glacial cycles, cold adapted biota recurrently expanded during glaciations and further became restricted into polar regions and high mountains during interglacial periods (Hewitt \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Parisod \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Wootton et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). These dynamics have shaped the biodiversity currently found in the Northern hemisphere mountains. In this scenario, the species had three options: migrate, adapt if they could not migrate, or get extinct if they could not migrate nor adapt efficiently (Nogu\u0026eacute;s-Bravo et al. 2018). Therefore, within the extant mountain species, we expect a filter towards good migration ability (Tovar et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) or strong alpine specialization leading to local endemicity (Kadereit \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDuring periods of glacial retreat, new opportunities for alpine plants to colonize previously ice-covered substrates arise, initiating a primary succession process that may evolve towards more complex communities with time and soil development (Dentant et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Leonelli et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Losapio et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Plants are key components of ecosystems, for instance, as primary producers fixing CO\u003csub\u003e2\u003c/sub\u003e, assimilating inorganic nutrients, creating soil or providing shelter and nutrition to other species. Consequently, their role in the colonization of recently deglaciated soils is crucial (Velasquez Casallas et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). In plants, gene flow can occur through pollen or seeds, but physical migration to occupy new territories when ice cover fluctuates is limited to seed dispersal. Although some lineages like Asteraceae present evident long distance dispersal syndromes (Mandel et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), not all alpine plant species do (Tovar et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePlant colonization after glacial retreat has been investigated in arctic and subarctic glaciers as well as in strongly glaciated mountain ranges such as the Andes (Anthelme et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and the Alps (Bayle et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Nota et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). However, research is still lacking in strongly deglaciated, warmer mountains where the persistence of glaciers in coming decades is not climatically sustainable (L\u0026oacute;pez-Moreno et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) and where, consequently, plant colonization is expected to be favoured and intense. Besides, some relict of glaciers often resist these temperate mountains in steep slopes sheltered from solar radiation in the upper slopes with northern aspect, where plant colonization is supposedly more challenging.\u003c/p\u003e \u003cp\u003eOpposite to the glaciers representing most study cases with ice tongues running through valleys with low or moderate slope (Vetaas \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Mathews and Vater 2015; Fickert \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Bayle et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Cantera et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Tanner et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), the retreat of steep glaciers in more thermic regions, like the Pyrenees, creates ice-free areas with strong altitudinal gradients where colonization dynamics remain poorly studied (Grunewald and Scheithauer \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). In these situations, upward plant colonization following the chronosequence is expected as a main pattern (Fisher et al. 2019, Losapio et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Alternatively, as these mountains have poorly vegetated peaks and ridges above the glaciers, downward plant colonization seems like an equally plausible scenario, but was never documented in deglaciated mountains such as the Pyrenees.\u003c/p\u003e \u003cp\u003eDescribing plant colonization processes in nearly extinct glaciers is key to assess the dynamics of the newly emerging mountain ecosystems in deglaciated areas, helping to understand past processes and generating knowledge for proper future conservation of these unique areas under climate change. The Pyrenees provide a unique opportunity to address this scientific challenge for different reasons: i) they host very small glaciers which are expected to disappear in the following decades ii) the cartography of the glaciers and their dynamics during the last decades is well documented and iii) the flora and vegetation of the Pyrenees is exhaustively described.\u003c/p\u003e \u003cp\u003eIn this study, we aim to understand how plant colonization takes place after the retreat of the Aneto glacier, located in the Central Pyrenees. Besides a description of the process, we want to test the following hypotheses: i) the plant community composition will differ between deglaciated slopes and never-glaciated nearby slopes, as well as within the deglaciated areas, depending on the ice retreat date, ii) plant diversity will decrease towards more recently deglaciated areas at higher altitudes, and iii) the source of plant colonization should include both lower elevation habitats and high elevation ridges resulting in coexisting upwards and downwards colonization processes.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003e \u003cb\u003eStudy site\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe study area is located at a north facing slope in the Maladeta massif in the Central Pyrenees (0.65\u0026deg;E, 42.64\u0026deg;N). It is right below the peaks of Maladeta (3312 m a.s.l.) and Aneto (3404 m a.s.l.), the latter being the highest peak in the Pyrenees (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The upper part of the slope is occupied by the Aneto glacier. It covered 34.4 ha in 2023 with a maximal length of ~\u0026thinsp;500 m between 3000 m a.s.l. and 3140 m a.s.l. (Izagirre et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The glacier front was down to ~\u0026thinsp;2500 m a.s.l. at the end of the LIA, from which it has consistently receded until now. The lower part of the slope is either bare granodiorite, detritic sediment or shallow soil and low vegetation (Vidaller et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eReconstruction of a chronosequence of the Aneto glacier front position\u003c/b\u003e \u003c/p\u003e \u003cp\u003eA time series of the front position of the Aneto glacier was created from aerial images, terrestrial photography, UAV imagery and airborne LiDAR and existing datasets (Vidaller et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Izagirre et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The front positions were retrieved from satellite images from 1990, 2000 and 2011, and images taken from UAV for the years 2020 and 2023. An aerial ortho-image at a 0.5 m resolution from the \u003cem\u003eAmerican flight\u003c/em\u003e program was used to retrieve the front position in 1946 and 1957. The front was retrieved at older dates in 1875 and 1934 from terrestrial photographs of mountaineers (i.e. Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The position of the highest frontal moraine observed on contemporary ortho-images was assumed to correspond to the LIA maximal extent around 1850 (Vidaller et al.2023). The historical terrestrial photographs were georeferenced by defining control points in the images and in a contemporary aerial image. Recognizable landmarks such as summits, faults, large rocks and vegetation patches were manually identified in archive and contemporary images. This processing was realized in the Monoplotting tool (Wiesmann et al.2012). The contemporary aerial image and the reference Digital Elevation Model (DEM) were provided by the Spanish national mapping agency (\u003cem\u003eInstituto Geogr\u0026aacute;fico Nacional-IGN\u003c/em\u003e). The aerial image was resampled from its native resolution of 0.25 m to 1 m to ease calculations. The DEM is derived from aerial lidar and has a resolution of 25 m. The reconstruction of the retreat chronosequence of Aneto glacier is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eVegetation surveys\u003c/b\u003e \u003c/p\u003e \u003cp\u003eField campaigns took place in August 2023 (deglaciated areas) and August 2024 (control areas) at comparable phenological stage. Vegetation was studied at nine sites of interest (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Taxonomic nomenclature followed G\u0026oacute;mez et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) as summarized in Appendix 1 (Supplementary material 1). Six of them were distributed along the deglaciation gradient of the Aneto glacier from the LIA (A1 to A6) and were randomly located within each deglaciation belt. As the glacial retreat is strongly associated with the altitude in the study area, an altitudinal control was set including three sites (C1 to C3) in an adjacent area with no evidence of permanent ice formation since the LIA and similar slope angle, bedrock and aspect. These control localities had a paired altitude with the sites A1 to A3. No control sites were selected at higher elevations since above that altitude no evident long-term ice-free areas were identified (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe deglaciation year of each plot was estimated using a linear interpolation based on the distances to the previous and next dated fronts as follows (details in Fig. \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e):\u003c/p\u003e \u003cp\u003e \u003cdiv id=\"Equa\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:Deglaciation\\:Year={Year}_{1}+\\left({Year}_{2}-\\:{Year}_{1}\\right)\\:\\times\\:\\:\\frac{{d}_{1}}{{{d}_{1}+d}_{2}}$$\u003c/div\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e\u0026hellip;where Year\u003csub\u003e1\u003c/sub\u003e and d\u003csub\u003e1\u003c/sub\u003e correspond to the dated year and distance from the plot to the previous front, and Year\u003csub\u003e2\u003c/sub\u003e and d\u003csub\u003e2\u003c/sub\u003e refer to the next front.\u003c/p\u003e \u003cp\u003eAt each site, 10 plots of 1 m by 1 m were set to maximize plant diversity estimation in the surroundings, separating them a minimum of 5 meters. A deglaciation year was associated with each site as the median of the deglaciation year of their 10 plots surveyed per site (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Each plot was divided into 25 cells of 0.2 x 0.2 m (Fig. S3), in which the presence of vascular plant species was recorded. Overall abundance of a species in a 1 x 1m plot was estimated as the frequency of presence in the 25 cells (i.e. 1/25 species only present in one cell and 25/25\u0026thinsp;=\u0026thinsp;1 if the species was present in all cells). Besides, the proportion of vegetation (including mosses), soil, and rock (including lichens if present) cover was visually evaluated in each cell and averaged for the plot.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eAnalysis of vegetation diversity and composition\u003c/b\u003e \u003c/p\u003e \u003cp\u003eFor each 1x1m plot, the diversity was estimated by means of the species richness (S) and Shannon Index (H\u0026rsquo;) (Shannon \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1948\u003c/span\u003e). For each site, accumulated species richness (γ diversity) was then calculated.\u003c/p\u003e \u003cp\u003eVegetation composition of each plot was visualized using NMDS and plotting the 95% confidence interval. We first plotted all 90 vegetation plots together and then separately those from the deglaciated area. Calculations were conducted with R-cran vegan package (Oksanen et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Jaccard similarity matrix comparing all 90 plots was subtracted.\u003c/p\u003e \u003cp\u003eTo account for the altitudinal preference of plant species in our study system, the Mean Occurrence Altitude (MOA) of each species in our dataset was calculated as its mean altitudinal occurrence in the dataset weighted by its abundance at each site. Species were then ordered according to their MOA values and classified in 100 metres altitudinal bands (from 2600 to 3000 m). To infer the potential origin of the species pool found in our study, we compared the inventories obtained from our sampling plots with the following three vegetation surveys (table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e): i) the Aneto peak (Fern\u0026aacute;ndez and Herreros \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2014\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, 2022), ii) \u003cem\u003eel Portill\u0026oacute;n\u003c/em\u003e mountain pass (Fern\u0026aacute;ndez and Herreros \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) and iii) \u003cem\u003eel Salterillo\u003c/em\u003e lake at the upper limit of dominant shrub vegetation below A1 point (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e for the location of the three localities). For all the species reported in the study, we recorded whether they were present in the \u003cem\u003eAneto\u003c/em\u003e, \u003cem\u003ePortill\u0026oacute;n\u003c/em\u003e and \u003cem\u003eSalterillo\u003c/em\u003e surveys and produced a MOA histogram colored accordingly. If a species was represented in two surveys, it was half weighted in each survey category.\u003c/p\u003e \u003cp\u003eAll figures were made with R-cran ggplot2 package (Wickham \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) in R studio 2024.04.2 except Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e5\u003c/span\u003e made in Microsoft Excel 2007 (Microsoft corporation).\u003c/p\u003e"},{"header":"3. Results","content":"\u003cp\u003e \u003cb\u003eRetreat of the Aneto glacier since 1850\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe front of the Aneto glacier showed a marked retreat between the dates defining the chronosequence studied. Between 1850 and 2023, the elevation of the glacier front increased by 28 m per decade on average and its length decreased by 85 m per decade, with nearly 80% reduction in 175 years (Fig. S4).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe median deglaciation year of sites A1 to A6 was inferred to be 1862, 1915, 1950, 1988, 2005 and 2009 respectively. Therefore the time since deglaciation to sampling varied from 163 years in A1 site to 15 years in A6 site, covering a chronosequence of 150 years (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Plots in A1 showed the highest variability in deglaciation year with a minimum-maximum range of 13 years, while the other points had a range between 1 and 6 years. The standard deviation of the deglaciation years was 3.3 years and 2.1 years for A1 and A2, and was always lower than 1.5 years for the other sampling areas. This shows the good homogeneity of the timing of deglaciation for a given sampling area and clear distinctiveness between survey sites in terms of deglaciation date.\u003c/p\u003e \u003cp\u003ePoints C1 and C2 were not covered with ice during this period, as they are outside the LIA moraine systems and appear ice free on the oldest available image from 1875 (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Point C3 was also likely not covered with ice during this period, but might have been below year-round persistent snowpack in early times as it appeared closer to small moraines in the field and to ice or snow on the 1875 image.\u003c/p\u003e \u003cp\u003e \u003cb\u003eSpecies composition along the ice retreat gradient\u003c/b\u003e \u003c/p\u003e \u003cp\u003eIn total, 65 species were recorded in the deglaciated area (A1-A6) and 98 in the control area (C1-C3), totaling 114 species(Supplementary material 2). Therefore, in the control area the species richness recorded was 50% higher than in the deglaciated area despite sampling half the plots (i.e thirty \u0026amp; sixty plots and three \u0026amp; six sites).\u003c/p\u003e \u003cp\u003eThe following seven species were recorded in all deglaciated sites: \u003cem\u003eLeucanthemopsis alpina, Linaria alpina, Gnaphalium supinum\u003c/em\u003e (\u003cem\u003eOmalotheca supina\u003c/em\u003e (L.) DC.in POWO \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2026\u003c/span\u003e), \u003cem\u003eOxyria digyna, Poa alpina, Saxifraga moschata\u003c/em\u003e and \u003cem\u003eVeronica alpina.Festuca glacialis\u003c/em\u003e was the most abundant species in A1 site, \u003cem\u003ePoa alpina\u003c/em\u003e in A2 and A3, \u003cem\u003eCerastium cerastoides\u003c/em\u003e in A4 and A5, and \u003cem\u003eVeronica alpina\u003c/em\u003e in A6. In the control area, the most common species across all plots were \u003cem\u003eVaccinium uliginosum, Festuca eskia, Trifolium alpinum and Thymus praecox\u003c/em\u003e. However, \u003cem\u003eCarex sempervirens\u003c/em\u003e dominated in C1, \u003cem\u003eVaccinium uliginosum\u003c/em\u003e in C2 and \u003cem\u003eSagina saginoides\u003c/em\u003e in C3. Table \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e summarizes the most relevant species in the study at site, plot and cell level.\u003c/p\u003e \u003cp\u003eThe composition of plant communities varied along the studied sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003eS5\u003c/span\u003e). Plots from the deglaciated and control sites clearly occupy different spaces in Non-metric Multidimensional Scaling (NMDS), indicating that they consistently had a different species composition. Control sites (C1-C3) did not overlap indicating that the vegetation composition of the control sites was different, yet not similar to the nearby deglaciated area. Clearly, C1 site appeared to be the most divergent and C2 and C3 laid in the periphery of the confidence interval inferred for deglaciated plots. The space within the 95% confidence interval was higher at C1 and C2 compared with sites A1 and A2 at the same altitude in the deglaciated area (see Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003eb together), a result aligned with the overall higher diversity values found in these sites (see next section).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAlthough the deglaciated plots shared more species and fell closer to each other in the NMDS space, there was a progressive differentiation from one edge to the other of the chronosequence (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Plots from the A1 site, an area deglaciated more than 150 years ago, showed very little within site variation in species composition. Moreover, the A1 plots were the ones closer to the C2 control site, whose vegetation was not influenced by permanent ice since the LIA. This indicates that vegetation composition in the A1 site is not yet similar to the nearby control areas after more than 150 years without an ice cover.\u003c/p\u003e \u003cp\u003eThe differences in species composition between deglaciated and control sites decreased with time since deglaciation (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). This process was associated with a decrease in within site variation in plant composition, although plant diversity values were higher (see next section). The plant species composition of plots in the C3 site, located near a moraine laid close to some A5 and A6 plots.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSite information and diversity values reported. Number of plots (N), altitude in meters (Alt.), median deglaciation year (DY), time since deglaciation (t), coordinates,γ, S and H\u0026rsquo; diversity and vegetation cover.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"11\" nameend=\"c11\" namest=\"c1\"\u003e \u003cp\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSite\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eN\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eAlt.\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eDY\u003c/b\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;sd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003et\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(years)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eCoord. (Long, Lat)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eγ\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eS\u003c/b\u003e\u003c/p\u003e \u003cp\u003ex\u0026thinsp;\u0026plusmn;\u0026thinsp;sd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eH\u0026rsquo;\u003c/b\u003e\u003c/p\u003e \u003cp\u003ex\u0026thinsp;\u0026plusmn;\u0026thinsp;sd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003eVeg. cover (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1862\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e163\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.65766, 42.65043\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e16,0\u0026thinsp;\u0026plusmn;\u0026thinsp;3,1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2,4\u0026thinsp;\u0026plusmn;\u0026thinsp;0,3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e46,0\u0026thinsp;\u0026plusmn;\u0026thinsp;10,2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2740\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1915\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.65516, 42.64814\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e12,6\u0026thinsp;\u0026plusmn;\u0026thinsp;3,9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2,2\u0026thinsp;\u0026plusmn;\u0026thinsp;0,3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e24,2\u0026thinsp;\u0026plusmn;\u0026thinsp;9,8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2870\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1950\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.65237, 42.64680\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9,8\u0026thinsp;\u0026plusmn;\u0026thinsp;3,5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1,8\u0026thinsp;\u0026plusmn;\u0026thinsp;0,4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e15,4\u0026thinsp;\u0026plusmn;\u0026thinsp;7,4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2920\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1988\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.65000, 42.64566\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8,6\u0026thinsp;\u0026plusmn;\u0026thinsp;2,8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1,8\u0026thinsp;\u0026plusmn;\u0026thinsp;0,4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e16,5\u0026thinsp;\u0026plusmn;\u0026thinsp;8,0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2960\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2005\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.64930, 42.64432\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7,5\u0026thinsp;\u0026plusmn;\u0026thinsp;2,2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1,7\u0026thinsp;\u0026plusmn;\u0026thinsp;0,2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e10,8\u0026thinsp;\u0026plusmn;\u0026thinsp;6,3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2009\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.64873, 42.64367\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4,5\u0026thinsp;\u0026plusmn;\u0026thinsp;2,1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1,2\u0026thinsp;\u0026plusmn;\u0026thinsp;0,6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e6,0\u0026thinsp;\u0026plusmn;\u0026thinsp;3,6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2580\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.65335, 42.65537\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e15,7\u0026thinsp;\u0026plusmn;\u0026thinsp;4,7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2,4\u0026thinsp;\u0026plusmn;\u0026thinsp;0,2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e64,0\u0026thinsp;\u0026plusmn;\u0026thinsp;35,0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.65161, 42.65466\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e19,9\u0026thinsp;\u0026plusmn;\u0026thinsp;5,4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2,6\u0026thinsp;\u0026plusmn;\u0026thinsp;0,3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e54,1\u0026thinsp;\u0026plusmn;\u0026thinsp;15,8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2870\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.64835, 42.65094\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8,4\u0026thinsp;\u0026plusmn;\u0026thinsp;3,6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1,7\u0026thinsp;\u0026plusmn;\u0026thinsp;0,6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e15,6\u0026thinsp;\u0026plusmn;\u0026thinsp;6,8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c11\" namest=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003ePlant cover and diversity along the ice retreat gradient\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTotal vegetation cover, species richness (S) and Shannon Index of species diversity (H\u0026rsquo;) increased steadily with time since deglaciation (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The average vegetation cover increased from less than 6% in recently deglaciated localities, to 46% in localities deglaciated about 163 years ago (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Species richness ranged between an average of 16 species per plot in the A1 site, deglaciated 163 years ago, to 4.5 species per plot in the A6 site, deglaciated 15 years ago (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). H\u0026rsquo; value also decreased by half from A1 point to A6 (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs the time since deglaciation is correlated with the altitude (Fig. S4), we investigated whether the diversity values exhibited a similar pattern between deglaciated and control areas, although species composition highly differed. Interestingly, the control sites, not covered with ice since the LIA, showed a different pattern than the sites located along the deglaciation gradient. Plant cover values in control sites were higher (significantly for C2 and A2 comparisons) and exhibited greater variability between plots of the same site (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Remarkably, C1 locality exhibited the highest variability with some plots with nearly 100% cover recorded. Whereas the diversity values decreased constantly along the deglaciation gradient (correlated with the altitude), in control sites the diversity increased despite the altitude between C1 and C2. Concretely the comparison between A2 and C2 gave a significant difference in species richness. Notably, C3 behaved similarly to the A3 point located at the same altitude in the glaciated area for all diversity and cover measures (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Finally, the ɣ diversity, the total species at each site, was considerably higher for control sites compared with the deglaciated sites at the same altitude (C1-A1 and C2-A2 in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Overall, these results demonstrate that the vegetation structure and diversity are not the same in control and deglaciated areas, despite sharing the local species pool, bedrock, orientation and climate.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eEvidence of plant colonization pathways\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTwo opposite plant colonization pathways were detected (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e5\u003c/span\u003e): (i) a bottom-up pathway, characterized by the presence of numerous species from Salterillo in the lower sector of the forefield, with a gradual decline in shared taxa at higher elevations (e.g. \u003cem\u003eAlchemilla alpina\u003c/em\u003e, \u003cem\u003eFestuca sp.\u003c/em\u003e, \u003cem\u003ePhyteuma hemisphaericum\u003c/em\u003e, \u003cem\u003eVaccinium uliginosum\u003c/em\u003e); and (ii) a top-down pathway, with summit-derived species from Aneto occurring predominantly in the upper elevation belt (~\u0026thinsp;3000 m), and including \u003cem\u003eSaxifraga pubescens\u003c/em\u003e, \u003cem\u003eAndrosace ciliata\u003c/em\u003e, \u003cem\u003eSaxifraga oppositifolia\u003c/em\u003e and \u003cem\u003eMinuartia sedoides\u003c/em\u003e. The proportion of species present in the Aneto summit decreased markedly at lower altitudes. No clear pattern was observed regarding the intermediate Portill\u0026oacute;n area.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003e \u003cb\u003eVegetation colonization following the ice retreat of the Aneto glacier\u003c/b\u003e \u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe Aneto glacier is a relict high alpine glacier occurring in a warm temperate mountain range (Vidaller et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), an environmental setting where research has been primarily focused on geomorphological processes after deglaciation, rather than plant colonization dynamics (Heckmann and Morche \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). It is located way above the treeline, restricting the species pool that can colonize deglaciated areas to strictly alpine and nival species, in contrast with the situation found in more septentrional glaciers, where lowland forest and tundra species pools can colonize deglaciated areas (Vetaas \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1994\u003c/span\u003e;Jones and del Moral \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2005\u003c/span\u003e;Burga et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Overall, this situation contributes to the novelty of our study and provides the opportunity to test whether most general patterns observed in highly glaciated mountain ranges are also found in less glaciated areas like the Pyrenees, or to point out at some particularities associated with the high mountain nature of the Aneto glacier.\u003c/p\u003e \u003cp\u003eOur relict alpine study system in Aneto glacier showed a strong correlation between altitude and the glacial retreat, contrasting with most previous similar studies focused in deglaciation glaciers with less altitudinal variation (Vetaas \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Mathews and Vater 2015; Fickert \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Bayle et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Cantera et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Tanner et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). An altitudinal control was set in a glacier free adjacent area to integrate the effect of altitude in vegetation composition. Although we identified non-glaciated areas near the deglaciated area, it was not possible to survey a complete altitudinal gradient free of ice and we are aware of that limitation imposed by the geomorphology and glacial dynamics (Burga et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Heckmann and Morche \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In any case, the plant composition, cover and diversity patterns observed in Aneto mountain suggest that plant colonization following ice retreat is a process highly decoupled from the process of community assembly that are at play in nearby areas that were not glaciated.\u003c/p\u003e \u003cp\u003eVegetation composition in non-glaciated areas, indeed, strongly differed from the vegetation found in deglaciated areas at similar altitudes. The total species richness found in the control area was 50% higher than in the deglaciated area which was investigated with more sampling effort (i.e. thirty plots at three control sites \u0026amp; sixty plots at six deglaciated sites) indicating that the species pool in the deglaciated area is strongly filtered. The control area presented communities widely found at the same altitude in the Aneto-Maladeta massif. C1 and C2 had deeper soils than any other studied locality, confirming long ice free periods that prevented soil erosion by the glacier. Therefore, dominant plants in these plots were grasses (e.g. \u003cem\u003eFestuca eskia\u003c/em\u003e), sedges (e.g. \u003cem\u003eCarex curvula\u003c/em\u003e) and different members of the Ericaceae family (e.g. \u003cem\u003eVaccinium uliginosum\u003c/em\u003e). These formations resemble tundra communities and are characterized by deep soils and long lived perennial grasses and shrubs (Chapin et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Shepelev et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), which is a widespread vegetation facies at similar altitudes in central siliceous Pyrenees (Carrillo, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Along the deglaciated area, both species composition and their frequency differed, with pioneers such as \u003cem\u003eLeucanthemompisis alpina, Armeria alpina, Sagina saginoides\u003c/em\u003e or \u003cem\u003eVeronica alpin\u003c/em\u003ea prevalent, including taxa that were not recorded in control areas (e.g. \u003cem\u003ePritzelago alpina\u003c/em\u003e or \u003cem\u003eLinaria alpina\u003c/em\u003e). Interestingly, most species found in our inventories in the deglaciated area were also found in early successional stages in similar studies in the Alps or the arctic, such as \u003cem\u003eSaxifraga\u003c/em\u003e species, \u003cem\u003eArabis alpina\u003c/em\u003e, \u003cem\u003ePoa alpina\u003c/em\u003e or \u003cem\u003eOxyria dygina\u003c/em\u003e (Burga et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Eichel \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This observation converges with the fact that 75% and 33% of the Pyrenean alpine flora is present in the Alps and Scandinavia, respectively (G\u0026oacute;mez et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e ).\u003c/p\u003e \u003cp\u003ePlant diversity estimations also showed clear differences between deglaciated and non-glaciated areas. Plant cover and diversity (S and H\u0026rsquo;) showed a progressive decline along the altitudinal gradient in the deglaciated slope (inversely correlated with time since deglaciation), contrasting with the unimodal distribution found in the non-glaciated area. Whereas the increase in diversity and plant cover is a common pattern found in primary succession following glacier retreat (Tapucci et al. 2015; Cantera et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e, Tanner et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Ficetola et al. 2025), a unimodal distribution of diversity with altitude is commonly found as a response to altitudinal gradients (Mark et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Fern\u0026aacute;ndez-Calzado et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sun et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Accordingly, the diversity patterns at small spatial scales are highly dependent on topological and microclimatic conditions, rather than colonization dynamics (Rydgren et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Opedal et al. 2014). In our control, C2 represented an area more heterogeneous than C1, hosting more diversity. In areas close to the limits of the glacier, as in C3, the vegetation suffered indirectly in different ways from the effect of having a big glacier nearby in the past. C3 was located in a landscape that combined lateral moraines and a scree originating from the erosion of nearby cliffs, and therefore did not fit an ideal control expectation. Consequently, vegetation composition in C3 differed from C1 and C2 and had lower cover and plant diversity values, as expected in less stable substrates (Burga et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), and resembled the deglaciated plots hosting more pioneer plants.\u003c/p\u003e \u003cp\u003eFor all the above, and despite the methodological limitations, our data provide strong evidence that the processes determining the composition and structure of vegetation differ between nearby deglaciated and non-deglaciated areas in Aneto mountain, and support the notion that the differences in vegetation found along the deglaciation chronosequence resulted mainly from primary succession and not altitudinal constraints.\u003c/p\u003e \u003cp\u003eAs expected after a glacier retreat, and contrasting with the control area, the results found in the deglaciation gradient evidenced an ongoing colonization process aligned with previous studies in other glaciated areas of the world (Jones et al 2003; Ficetola et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Losapio et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Vegetation cover and diversity measures provided evidence that plant communities gained species and structure through time since ice retreat (Bayle et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Ficetola et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The Aneto glacier retreat left an extensive granite surface eroded with very few cracks and spots favorable for plant establishment after the ice retreat (Fig. S7). With time, in certain areas where water and sediments accumulated, the soil started to develop allowing plant colonization. These dynamics also found in other glaciers explain why long deglaciated plots exhibited more plant cover and species diversity than recently deglaciated ones (Eichel, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). It is expected that, on a long term, the vegetation of deglaciated areas will evolve to grass and shrub dominated communities more similar to C1 and C2, as plant dispersal is feasible and altitude, slope and orientation are similar.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eInterestingly, the plots located in areas deglaciated more than a century and a half ago retained different plant species to non-glaciated areas, indicating that homogenization of vegetation between control and deglaciated areas may require considerable more time. This contrasts with general findings in more conventional glaciers which estimated a century as the minimum time needed until surrounding mature communities completely colonized deglaciated areas (Burga et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Ficetola et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Moreover, a common pattern described in the literature is that plant diversity tends to diminish once plant communities reach maturity (Tampucci et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Glausen and Tanner. 2019; Tanner et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and replacement prevails over the addition of species (Cantera et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). These situations were not found in our system yet, reinforcing the idea that the colonization process that started after LIA is still ongoing. This delay in colonization is likely explained by the slowdown of biological processes at high altitude (K\u0026ouml;rner \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), or by the snow legacy (Choler et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), and may need up to four centuries (Cantera et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eOur data suggest that the development of plant communities in these periglacial areas is largely dependent on ice-free time, expected to be associated with soil development (Ficetola et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e and 2014, Losapio et al. 2015). This contrasts with previous findings in our study area showing a weak pattern in soil structure along the same deglaciation gradient (Vidaller et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), but this lack of correlation was also found by Wei et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). This fact clearly indicates the need of further studies to couple soil and vegetation processes, because their dynamics do not respond necessarily to the same factors and they have to be studied simultaneously under the same design (Wei et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Ficetola et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). First of all, sediments are transported by ice, so the glacier retreat does not imply a time 0 for soil formation, as it does for plant colonization; soil can be developed already under the ice (Heckmann and Morche, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Besides, primary soil development depends on the equilibrium between sedimentation and disturbances (Ficket and Gruninger, 2018) and in proper spots, soil will develop and structure with time (Wei et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Finally, plants themselves are the most important agents to develop proper organic soils on top of the initial mineral soils (Eichel \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and its presence is positively linked with other components of the ecosystem (Ficetola et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). As the plant colonization process in the deglaciated gradient is not completed, we consider that the match between soil development in bare and vegetated areas is expected to be uncoupled.\u003c/p\u003e \u003cp\u003e \u003cb\u003eDrivers of vegetation colonization in the deglaciated areas of the Aneto glacier\u003c/b\u003e \u003c/p\u003e \u003cp\u003ePlant colonization in deglaciated areas is expected to occur mainly from communities surrounding the glacier area. Most successional studies along glacial retreat chronosequences have been conducted in tongs of large glaciers (Vetaas \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Jones and de Moral, 2005; Glaussen and Tanner, 2019; Nota et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), where the main colonization sources may be located not only below the glacier, but also in the surrounding slopes at higher altitudes also hosting similar plant communities. Opposite to that situation, the Aneto glacier is restricted to the upper part of the highest mountain in the Pyrenees. This limits the main potential colonization sources in the study system to two, one below the glacier and another one above it, including the ridges and summits. Concretely, the LIA maximum extent of the glacier is now surrounded by alpine grasslands of \u003cem\u003eFestuca eskia\u003c/em\u003e and \u003cem\u003eNardus stricta\u003c/em\u003e, combined with heath shrubs which dominate at altitudinal ranges between 2200 and 2500 meters, similar to the lower control areas. However, the Aneto glacier is now restricted to the nival belt at altitudes above 3000 meters, so the upper front of the glacier is surrounded by rocky ridges where very few plants grow. Still, among them there are several endemic (i.e \u003cem\u003eSaxifraga iratiana\u003c/em\u003e, \u003cem\u003eAndrosace ciliata\u003c/em\u003e) or boreoalpine taxa (i.e \u003cem\u003eRanunculus glacialis\u003c/em\u003e, \u003cem\u003eArabis alpina\u003c/em\u003e), which have their growing optimum at this altitude. They are postulated to be cold adapted plants, which find refuge in the coldest part of the mountain, and are at risk of local extinction as the vegetation of the mountain tops increases its richness (Steinbauer et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAn interesting finding of this study is that colonization following ice retreat in the Aneto glacier took place in two directions: upward and downward. In the upper part of the deglaciated area, there were species also found at the top of the Aneto mountain, which are representative of the vegetation found along the Aneto-Maladeta ridge above the glacier. These species decreased drastically at lower altitudes. We interpret this as an effect of gravity directly or, indirectly, through water flows that may transport the seeds of these high alpine plants from the ridges. In parallel, the vegetation found in the lower part of the deglaciated area, even if different in overall plant composition from the non-glaciated surrounding areas, shared more than half of the species with the nearby source communities, here represented with vegetation surveys conducted in the surroundings of Salterillo lake. The percentage of species shared with Salterillo decreased towards the upper part of the deglaciated part of the glacier. It is remarkable that although altitude is not strongly determining the colonization and diversity patterns along the chronosequence it plays an important role determining the species source for the colonization.\u003c/p\u003e \u003cp\u003eTo the best of our knowledge, this is the first evidence of an altitude-structured plant colonization source following glacier retreat, and may be explained by the high altitude and relict nature of the Aneto glacier, not shared with most previous studies. This finding also highlights the ecological relevance of in situ survival of plants in nunataks, which have long been discussed in the Pyrenees (Segarra-Moragues 2007; Carnicero et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Finally, from a conservation perspective, our results provide strong evidence that in high alpine nearly extinct glaciers, the colonization of newly opened ice free areas may serve as an opportunity for rare and climatically threatened alpine species to extend their potential range. In five to ten years, a revisit of the Aneto area should be undertaken to document the future evolution of plant colonization in the area. To this end, the GPS coordinates and pictures (lateral and zenithal) of each plot were taken to ensure reproducibility of the inventories in the future.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe Aneto glacier represents a unique study system to understand the colonization processes not only along a glacier retreat chronosequence at high elevation and steep slopes, but also in a situation where glacier disappearance is expected in a few years period. The vegetation along the deglaciation gradient in the Aneto glacier follows an expected pattern of increase of cover and diversity since the LIA, with a different composition from the non-glaciated surrounding areas. After more than a century and a half, these differences are still notorious, and the successional dynamics seem to be ongoing. The main species source for colonization of the deglaciated area in Aneto is the vegetation from lower altitudes, but colonization of the higher part of the deglaciation gradient is strongly dominated by plants growing in the tops and ridges of the massif, providing and evidence of a complementary downwards colonization process. Similar patterns of colonization to those described here can be expected in other glaciers of the Pyrenees. Besides, differences in the colonization pattern can be expected with different topography, bedrocks, climate and native vegetation. Studying in a similar way other periglacial areas of the Pyrenees would enable to evaluate the generality of the patterns highlighted here and the potential for alpine plant species conservation in the context of climate change.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe study was designed by PT, CSB, JILM, JR, SP with the assistance of IV, OF, SL and PR. Field work was conducted by PT, CDB, NCR, FRH, AA, ALV, OF. The analyses and figure production were conducted by NCR, AA, CDB and PT. Writing and edition of the manuscript was led by PT and CDB. The review and edition of the manuscript has been accomplished by all authors who gave final approval for publication.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis study was supported by the POCTEFA program from the EU through FLORAPYR 3D (EFA064/01) project, the Spanish Ministry of Science and Innovation through MARGISNOW (PID2021-124220OB-100) project and postdoctoral grant (FJC2021‐047268‐I)), the Leonardo program of the BBVA research foundation through MeltingIce project and the French Space Agency (Centre National d'Etudes Spatiales, CNES) through a postdoctoral fellowship. Jaca Herbarium has allocated its own resources to the study. We thank the authorities of the Posets-Maladata Natural Park for the support to our study. We also thank Idoia Biurrun from the UPV-EHU for her comments and suggestions.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe dataset generated and analyzed during the current study is available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnthelme F, Carrasquer I, Ceballos JL, Peyre G (2022) \\ \\ Novel\\ plant\\ communities\\ after\\ glacial\\ retreat\\ in\\ Colombia:\\ \\(many\\)\\ losses\\ and\\ \\(few\\)\\ gains\\.\\ \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www\\.zotero\\.org/google\\-docs/\\?06zzd5\u003c/span\u003e\u003cspan address=\"https://www\\.zotero\\.org/google\\-docs/\\?06zzd5\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\\ \\h\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBayle A, Carlson BZ, Zimmer A, Vall\u0026eacute;e S, Rabatel A, Cremonese E et al (2023) Local environmental context drives heterogeneity of early succession dynamics in alpine glacier forefields. \u003cem\u003eBiogeosciences20\u003c/em\u003e(8):1649\u0026ndash;1669. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5194/bg-20-1649-2023\u003c/span\u003e\u003cspan address=\"10.5194/bg-20-1649-2023\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBosson JB, Huss M, Cauvy-Frauni\u0026eacute; S, Cl\u0026eacute;ment JC, Costes G, Fischer M et al (2023) Future emergence of new ecosystems caused by glacial retreat. Nature. 620(7974):562\u0026ndash;569. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41586-023-06302-2\u003c/span\u003e\u003cspan address=\"10.1038/s41586-023-06302-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurga CA, Frauenfelder R, Ruffet J, Hoelzle M, K\u0026auml;\u0026auml;b A (2004) Vegetation on Alpine rock glacier surfaces: a contribution to abundance and dynamics on extreme plant habitats. Flora 199(6):505\u0026ndash;515. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1078/0367-2530-00179\u003c/span\u003e\u003cspan address=\"10.1078/0367-2530-00179\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurga CA, Kr\u0026uuml;si B, Egli M, Wernli M, Elsener S, Ziefle M, Fischer T, Mavris C (2010) Plant succession and soil development on the foreland of the Morteratsch glacier (Pontresina, Switzerland): Straight forward or chaotic? Flora 205(9):561\u0026ndash;576. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.flora.2009.10.001\u003c/span\u003e\u003cspan address=\"10.1016/j.flora.2009.10.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCantera I, Carteron A, Guerrieri A et al (2024) The importance of species addition \u0026lsquo;versus\u0026rsquo; replacement varies over succession in plant communities after glacier retreat. Nat Plants 10:256\u0026ndash;267. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41477-023-01609-4\u003c/span\u003e\u003cspan address=\"10.1038/s41477-023-01609-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarnicero P, Wessely J, Moser D, Font X, Dullinger S, Sch\u0026ouml;nswetter P (2022) Postglacial range expansion of high-elevation plants is restricted by dispersal ability and habitat specialization. J Biogeogr 49:1739\u0026ndash;1752. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/jbi.14390\u003c/span\u003e\u003cspan address=\"10.1111/jbi.14390\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarrillo A (1984) La Flora i la Vegetacio de l'Alta muntanya de les Valls d'Espot i de Boi (Pirineus Centrals). PhD. Universitat de Barcelona\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChapin FS, Jefferies RL, Reynolds JF, Shaver GR, Svoboda J (1992) Arctic Ecosystems in a Changing Climate. Academic, Inc.San Diego, CA\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCholer P, Bonfanti N, Reverdy A et al (2025) Legacy of snow cover on alpine landscapes. Commun Earth Environ 6:758. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s43247-025-02702-6\u003c/span\u003e\u003cspan address=\"10.1038/s43247-025-02702-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDentant C, Carlson BZ, Bartalucci N, Bayle A, Lavergne S (2024) Anthropocene trajectories of high alpine vegetation on Mont-Blanc nunataks. Bot Lett 171(1):65\u0026ndash;79. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/23818107.2023.2231503\u003c/span\u003e\u003cspan address=\"10.1080/23818107.2023.2231503\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDussaillant I, Hugonnet R, Huss M, Berthier E, Bannwart J, Paul F, Zemp M (2025) Annual mass change of the world\u0026rsquo;s glaciers from 1976 to 2024 by temporal downscaling of satellite data with in situ observations. Earth Syst Sci Data 17(5):1977\u0026ndash;2006. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5194/essd-17-1977-2025\u003c/span\u003e\u003cspan address=\"10.5194/essd-17-1977-2025\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEichel J (2019) Vegetation succession and biogeomorphic interactions in glacier forelads. In: Heckmann T, Morche D (eds) Landform and sediment dynamics in recently deglaciated alpine landscapes, vol 327. Springer, Switzerland, p 350\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFern\u0026aacute;ndez O, Herreros MJ (2014) Seguimiento de la diversidad flor\u0026iacute;stica en las cumbres del Pirineo aragon\u0026eacute;s. Instituto de Estudios Altoaragoneses\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFern\u0026aacute;ndez O, Herreros MJ (2019) 2022) Seguimiento de la diversidad flor\u0026iacute;stica en las cumbres del Parque Natural Posets-Maladeta como indicador de cambios. Gobierno de Arag\u0026oacute;n\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFern\u0026aacute;ndez-Calzado R, Ghosn D, Gottfried M, Kazakis G, Molero Mesa J, Pauli H, Merzouki A (2013) Modelos de endemicidad a lo largo de un gradiente altitudinal en Sierra Nevada (Espa\u0026ntilde;a) y Lefka Ori (Creta, Grecia). Pirineos 168:7\u0026ndash;24. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3989/Pirineos.2013.168001\u003c/span\u003e\u003cspan address=\"10.3989/Pirineos.2013.168001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFicetola GF, Marta S, Guerrieri A, Gobbi M, Ambrosini R, Fontaneto D, Zerboni A, Poulenard J, Caccianiga M, Thuiller W (2021) Dynamics of Ecological Communities Following Current Retreat of Glaciers. Annu Rev Ecol Evol Syst 52:405\u0026ndash;426. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1146/annurev-ecolsys-010521040017\u003c/span\u003e\u003cspan address=\"10.1146/annurev-ecolsys-010521040017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFicetola GF, Marta S, Guerrieri A, Cantera I, Bonin A, Cauvy-Frauni\u0026eacute; S et al (2024) The development of terrestrial ecosystems emerging after glacier retreat. \u003cem\u003eNature632\u003c/em\u003e(8024):336\u0026ndash;342. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41586-024-07778-2\u003c/span\u003e\u003cspan address=\"10.1038/s41586-024-07778-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFickert T, Gr\u0026uuml;ninger F (2018) High-speed colonization of bare ground\u0026mdash;Permanent plot studies on primary succession of plants in recently deglaciated glacier forelands. Land Degrad Dev 29:2668\u0026ndash;2680. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/ldr.3063\u003c/span\u003e\u003cspan address=\"10.1002/ldr.3063\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFickert T (2020) Common patterns and diverging trajectories in primary succession of plants in eastern alpine glacier forelands. Diversity 12:191. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/d12050191\u003c/span\u003e\u003cspan address=\"10.3390/d12050191\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGlausen TG, Tanner LH (2019) Successional trends and processes on a glacial foreland in Southern Iceland studied by repeated species counts. Ecol Process 8:11. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/s13717-019-0165-9\u003c/span\u003e\u003cspan address=\"10.1186/s13717-019-0165-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrunewald K, Scheithauer J (2010) Europe\u0026rsquo;s southernmost glaciers: response and adaptation to climate change. J Glaciol 56(195):129\u0026ndash;142. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3189/002214310791190947\u003c/span\u003e\u003cspan address=\"10.3189/002214310791190947\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eG\u0026oacute;mez D, Ferr\u0026aacute;ndez JV, Bernal M, Campo A, Retamero JRL, Ezquerra V (2020) Plantas de las cumbres del Pirineo. PRAMES. Zaragoza\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeckmann T, Morche D (2019) Landform and sediment dynamics in recently deglaciated alpine landscapes. Springer, Switzerland\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHewitt G (1999) Post-glacial re-colonization of European biota. Biol J Linn Soc 68(1\u0026ndash;2):87\u0026ndash;112. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1095-8312.1999.tb01160.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1095-8312.1999.tb01160.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHock R, Rasul G, Adler C, C\u0026aacute;ceres B, Gruber S, Hirabayashi Y, Jackson M, K\u0026auml;\u0026auml;b A, Kang S, Kutuzov S, Milner Al, Molau U, Morin S, Orlove B, Steltzer H (2019) High Mountain Areas. In: P\u0026ouml;rtner HO, Roberts DC, Masson-Delmotte V, Zhai P, Tignor M, Poloczanska E, Mintenbeck K, Alegr\u0026iacute;a A, Nicolai M, Okem A, Petzold J, Rama B, Weyer NM (eds) IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp 131\u0026ndash;202. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1017/9781009157964.004\u003c/span\u003e\u003cspan address=\"10.1017/9781009157964.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIzagirre E, Revuelto J, Vidaller I, Deschamps-Berger C, Rojas-Heredia F, Rico I et al (2024) Pyrenean glaciers are disappearing fast: state of the glaciers after the extreme mass losses in 2022 and 2023. Reg Environ Change 24:172. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e.https://doi.org/10.1007/s10113-024-02333-1\u003c/span\u003e\u003cspan address=\".10.1007/s10113-024-02333-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJones C, del Moral R (2005) Patterns of Primary Succession on the Foreland of Coleman Glacier, Washington, USA. (2005). Plant Ecol. 180:105\u0026ndash;116. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11258-005-2843-1\u003c/span\u003e\u003cspan address=\"10.1007/s11258-005-2843-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKadereit JW (2024) The uneven distribution of refugial endemics across the European Alps suggests a threefold role of climate in speciation of refugial populations. Alp Bot 134:29\u0026ndash;50. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00035-024-00306-y\u003c/span\u003e\u003cspan address=\"10.1007/s00035-024-00306-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK\u0026ouml;rner C (2003) Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystems (2nd edition). Springer, Berlin\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeonelli G, Masseroli A, Trombino L, Golzio A, Bonetti A, Maggi V et al (2024) Development of the critical zone environment in the highly dynamic landscape of the Forni Glacier forefield: Winds, tree vegetation, pedogenesis and surface waters after glacier retreat. Earth Surf Process Landf 49(14):4587\u0026ndash;4609. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/esp.5983\u003c/span\u003e\u003cspan address=\"10.1002/esp.5983\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL\u0026oacute;pez-Moreno JI, Revuelto J, Izagirre E, Alonso-Gonz\u0026aacute;lez E, Vidaller I, Bonsoms J (2025) No hope for Pyrenean glaciers. Ann Glaciol 66:e17. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1017/aog.2025.10015\u003c/span\u003e\u003cspan address=\"10.1017/aog.2025.10015\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLosapio G, Lee JR, Fraser CI, Gillespie MAK, Kerr NR, Zawierucha K, Hamilton TL et al (2025) Impacts of deglaciation on biodiversity and ecosystem function. Nat Rev Biodivers 1(6):371\u0026ndash;385. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s44358-025-00049-6\u003c/span\u003e\u003cspan address=\"10.1038/s44358-025-00049-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMandel JR, Dikow RB, Siniscalchi CM, Thapa R, Watson LE, Funk VA (2019) A fully resolved backbone phylogeny reveals numerous dispersals and explosive diversifications throughout the history of Asteraceae. Proc Natl Acad Sci USA 9(28):14083\u0026ndash;14088. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1073/pnas.1903871116\u003c/span\u003e\u003cspan address=\"10.1073/pnas.1903871116\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMark AF, Dickinson KJM, Hofstede RGM (2000) Alpine Vegetation, Plant Distribution, Life Forms, and Environments in a Perhumid New Zealand Region: Oceanic and Tropical High Mountain Affinities. Arct Antarct Alp Res 32(3):240\u0026ndash;254. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/15230430.2000.12003361\u003c/span\u003e\u003cspan address=\"10.1080/15230430.2000.12003361\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNogues-Bravo D, Rodr\u0026iacute;guez-S\u0026aacute;nchez F, Orsini L, de Boer E, Jansson R, Morlon H, Fordham DA, Jackson ST (2018) Cracking the code of biodiversity responses to past climate change. Trends Ecol Evol 33(10):765\u0026ndash;776. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.tree.2018.07.005\u003c/span\u003e\u003cspan address=\"10.1016/j.tree.2018.07.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNota G, Enri SR, Lonati M, Mainetti A (2025) Faster than expected: 5-year re-surveys reveal accelerating plant colonization in two proglacial forelands of the Gran Paradiso National Park (NW Italian Alps). Bot J Linn Soc 207(3):266\u0026ndash;278. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/botlinnean/boae043\u003c/span\u003e\u003cspan address=\"10.1093/botlinnean/boae043\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOpedal \u0026Oslash;H, Armbruster WS, Graae BJ (2015) Linking small-scale topography with microclimate, plant species diversity and intra-specific trait variation in an alpine landscape. Plant Ecol Divers 8(3):305\u0026ndash;315. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/17550874.2014.987330\u003c/span\u003e\u003cspan address=\"10.1080/17550874.2014.987330\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOksanen J, Simpson GL, Blanchet FG, Kindt R, Legendre P, Minchin PR et al (2025) vegan: Community Ecology Package. R package version X.Y-Z. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://CRAN.R-project.org/package=vegan\u003c/span\u003e\u003cspan address=\"https://CRAN.R-project.org/package=vegan\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParisod C (2008) Postglacial recolonisation of plants in the western Alps of Switzerland. Bot Helv 118:1\u0026ndash;12. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00035-008-0825-3\u003c/span\u003e\u003cspan address=\"10.1007/s00035-008-0825-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRStudio: Integrated Development Environment for R.Posit Software, PBC, Posit team, Boston (2025) MA. URL \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.posit.co/\u003c/span\u003e\u003cspan address=\"http://www.posit.co/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePOWO (2026) Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew.\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://powo.science.kew.org/\u003c/span\u003e\u003cspan address=\"https://powo.science.kew.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e Retrieved 05 January 2026\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRydgren K, Halvorsen R, T\u0026ouml;pper JP, Nj\u0026oslash;s JM (2014) Glacier foreland succession and the fading effect of terrain age. J Veg Sci 25:1367\u0026ndash;1380. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/jvs.12184\u003c/span\u003e\u003cspan address=\"10.1111/jvs.12184\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchuster L, Maussion F, Rounce D, Ultee L, Schmitt P, Lacroix F, Fr\u0026ouml;licher TL, Schleussner CF (2025) Irreversible glacier change and trough water for centuries after overshooting 1.5\u0026deg;C. Nat Clim Chang 15:634\u0026ndash;641. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41558-025-02318-w\u003c/span\u003e\u003cspan address=\"10.1038/s41558-025-02318-w\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShannon CE (1948) A mathematical theory of communication. Bell Syst Tech J 27(3):379\u0026ndash;423. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/j.1538-7305.1948.tb01338.x\u003c/span\u003e\u003cspan address=\"10.1002/j.1538-7305.1948.tb01338.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShepelev AG, Efimova AP, Maximov TC (2025) Carbon Stocks and Microbial Activity in the Low Arctic Tundra of the Yana\u0026ndash;Indigirka Lowland, Russia. Land 14(9):1839. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/land14091839\u003c/span\u003e\u003cspan address=\"10.3390/land14091839\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSegarra-Moragues JG, Palop-Esteban M, Gonz\u0026aacute;lez-Candelas F, Catal\u0026aacute;n P (2007) Nunatak survival vs. tabula rasa in the Central Pyrenees: a study on the endemic plant species Borderea pyrenaica (Dioscoreaceae). J Biogeogr 34:1893\u0026ndash;1906. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1365-2699.2007.01740.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1365-2699.2007.01740.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSteinbauer MJ, Grytnes JA, Jurasinski G et al (2018) Accelerated increase in plant species richness on mountain summits is linked to warming. Nature 556:231\u0026ndash;234. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41586-018-0005-6\u003c/span\u003e\u003cspan address=\"10.1038/s41586-018-0005-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun L, Luo J, Qian L, Deng T, Sun H (2020) The relationship between elevation and seed-plant species richness in the Mt. Namjagbarwa region (Eastern Himalayas) and its underlying determinants. Glob Ecol Conserv 23e01053. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.gecco.2020.e01053\u003c/span\u003e\u003cspan address=\"10.1016/j.gecco.2020.e01053\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThe GlaMBIE Team, Zemp M, Jakob L, Dussaillant I, Nussbaumer SU, Gourmelen N et al (2025) Community estimate of global glacier mass changes from 2000 to 2023. Nature 639(8054):382\u0026ndash;388. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41586-024-08545-z\u003c/span\u003e\u003cspan address=\"10.1038/s41586-024-08545-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTanner L, Kikukawa G, Weits K (2024) The temporal and spatial dynamics of succession in a glacial foreland in southern Iceland: the effects of landscape heterogeneity. Land 13(7):1055. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/land13071055\u003c/span\u003e\u003cspan address=\"10.3390/land13071055\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTampucci D, Gobbi M, Boracchi P, Cabrini E, Compostella C, Mangili F, Marano G, Pantini P, Caccianiga M (2015) Plant and arthropod colonisation of a glacier foreland in a peripheral mountain range. Biodiversity 16(4):213\u0026ndash;223. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://doi.org/10.1080/14888386.2015.1117990\u003c/span\u003e\u003cspan address=\"10.1080/14888386.2015.1117990\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTovar C, Melcher I, Kusumoto B et al (2020) Plant dispersal strategies of high tropical alpine communities across the Andes. J Ecol 108:1910\u0026ndash;1922. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/1365-2745.13416\u003c/span\u003e\u003cspan address=\"10.1111/1365-2745.13416\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVelasquez Casallas LM, Khelidj N, Mor\u0026aacute;n-Ord\u0026oacute;\u0026ntilde;ez A, Losapio G (2025) Global impacts of glacier retreat on ecosystem services provided by soil and vegetation in mountain Regions: A literature review. Ecosyst Serv 73:101730. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ecoser.2025.101730\u003c/span\u003e\u003cspan address=\"10.1016/j.ecoser.2025.101730\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVetaas OR (1994) Primary Succession of Plant Assemblages on a Glacier Foreland\u0026ndash;B\u0026oslash;dalsbreen, Southern Norway. J Biogeogr 21(3):297\u0026ndash;308. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2307/2845531\u003c/span\u003e\u003cspan address=\"10.2307/2845531\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVidaller I, Izagirre E, Del Rio LM, Alonso-Gonz\u0026aacute;lez E, Rojas-Heredia F, Serrano E et al (2023) The Aneto glacier\u0026rsquo;s (Central Pyrenees) evolution from 1981 to 2022: ice loss observed from historic aerial image photogrammetry and remote sensing techniques, vol 17. Cryosphere, pp 3177\u0026ndash;3192. 8\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5194/tc-17-3177-2023\u003c/span\u003e\u003cspan address=\"10.5194/tc-17-3177-2023\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVidaller I, Otero XL, Igual JM, Nobrega GN, Ferreira TO, Moreno A, L\u0026oacute;pez-Moreno JI (2025) Incipient soils: New habitats in proglacial areas of the Maladeta massif (Central Pyrenees). Sci Total Environ 967:178740. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.scitotenv.2025.178740\u003c/span\u003e\u003cspan address=\"10.1016/j.scitotenv.2025.178740\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWei T, Shangguan D, Yi S, Ding Y (2021) Characteristics and controls of vegetation and diversity changes monitored with an unmanned aerial vehicle (UAV) in the foreland of the Urumqi Glacier 1, Tianshan, China. Sci Total Environ 771. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.scitotenv.2021.145433\u003c/span\u003e\u003cspan address=\"10.1016/j.scitotenv.2021.145433\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWickham H (2016) ggplot2: Elegant Graphics for Data Analysis. Springer-, New York. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://ggplot2.tidyverse.org\u003c/span\u003e\u003cspan address=\"https://ggplot2.tidyverse.org\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWiesmann S, Steiner L, Pozzi M, Bozzini C, Bauder A, Hurni L (2012) Reconstructing Historic Glacier States Based on Terrestrial Oblique Photographs. Proceedings - AutoCarto 2012 - Columbus, Ohio, USA\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhittaker RH (1978) Classification of vegetation. Dr W. Junk, The Hague, NL\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWootton LM, Boucher FC, Renaud J, Valla PG, Midolo G, Lososov\u0026aacute; Z, Thuiller W, Lavergne S (2025) The Limited Legacy of Post-Glacial Recolonization in the Floristic Patterns of the European Alps. Syst Bot 50(1):83\u0026ndash;98. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1600/036364425X17466502618876\u003c/span\u003e\u003cspan address=\"10.1600/036364425X17466502618876\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Glacial retreat, Chronosequence, Primary plant succession, Aneto glacier","lastPublishedDoi":"10.21203/rs.3.rs-8663348/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8663348/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eGlacier surface is decreasing worldwide and deglaciated land provides a unique opportunity to study plant colonization and primary ecological succession in alpine ecosystems. Most previous research on the topic has been conducted in strongly glaciated regions hosting the most important glacier systems. Contrastingly, little research has been conducted in thermic mountains with relict glaciers near extinction like those of the Pyrenees. The highest peak in the Pyrenees, Aneto, hosts a glacier that has dramatically shrunk in recent decades, and is currently restricted to upper slopes near the ridgeline. To understand plant succession and colonization in a system representative of relictual thermic glaciers, we conducted vegetation surveys along the deglaciation chronosequence of the Aneto glacier, from the Little Ice Age (LIA) to date. We identified vascular plant species present in 60 plots at 6 different sites along the deglaciation gradient, recording 65 different species in total. Plant composition was different between the deglaciated area and nearby control surveys conducted in adjacent unglaciated areas where diversity was higher. Moreover, plant diversity decreased towards recently deglaciated areas, and plant composition became more stochastic. Interestingly, we found evidence that colonization in the lower part of the deglaciated slope was based on the species pool of non glaciated areas below the glacier and colonization of the upper part was also strongly influenced by downward colonization from species native to the ridges. Consequently, although the altitude is not the main driver of the colonization process along the chronosequence, it has a relevant role in determining the species source.\u003c/p\u003e","manuscriptTitle":"Upward and downward colonization of vegetation following the retreat of the Aneto glacier, since the Little Ice Age","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-27 19:27:14","doi":"10.21203/rs.3.rs-8663348/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4a7ebe9e-3cba-44b9-bb93-20e632a48b60","owner":[],"postedDate":"January 27th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-04T16:09:57+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-27 19:27:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8663348","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8663348","identity":"rs-8663348","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}