Differential Adaptation of Eucalyptus Species through Morpho-physiological and Hydraulic Adjustments to Climate Variability

Differential Adaptation of Eucalyptus Species through Morpho-physiological and Hydraulic Adjustments to Climate Variability | 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 Differential Adaptation of Eucalyptus Species through Morpho-physiological and Hydraulic Adjustments to Climate Variability Sondes Fkiri, Awatef Slama, Fadwa Yahya, Yassine Yahia, Hamdi Bendif, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8554718/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 3 You are reading this latest preprint version Abstract Regenerating forests must adapt to prevailing climatic conditions for several decades, and possibly over a century. Climate change is profoundly altering tree productivity and ecophysiological responses, with major impacts on forest ecosystems. Understanding the capacity of forest tree species to adapt to climate change, particularly drought, is therefore crucial for sustainable forest management. This study investigates variability in the physiological behavior of three Eucalyptus species ( E. camaldulensis , E. maculata , E. paniculata ) growing under two bioclimates (humid and sub-humid). Gas exchange, hydraulic traits, morphological characteristics, and water availability were monitored to evaluate species performance. Significant differences in adaptive behavior were observed across species and sites ( p < 0.05 ). The Sejnane provenance (humid) showed superior water status and physiological tolerance to drought compared with Rimel (sub-humid), reflecting better adaptation with lower evapotranspiration and water deficit. Morphological adjustments contributed to improved physiological performance under limited water. E. paniculata displayed strong acclimation to both sites, maintaining efficient water control under stress, while E. camaldulensis showed limited adaptive capacity. These findings are essential for identifying drought-resilient tree species suited for reforestation, supporting sustainable forest management and ecosystem restoration under changing climatic conditions. Eucalyptus spp. drought tolerance morpho-physiological adaptation hydraulic traits gas exchange water-use efficiency climatic variability Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction In recent years, global warming and climate change have become central topics of concern for environmentalists worldwide. Forests—like all natural ecosystems—are increasingly exposed to these climatic shifts. Developing effective forest management strategies is therefore essential for selecting superior forest reproductive material and improving plantation performance under changing climate scenarios (Guarnaschelli et al., 2012 ). Under such circumstances, forest productivity can only be sustained by selecting species with greater tolerance to low water availability (Linder, 2000; Villar et al., 2011; Correia et al., 2014 ). To minimize the negative effects of climate change on plant communities, particularly forests, it is crucial to protect, maintain, and enhance forest ecosystems while promoting their capacity for carbon sequestration. Climate change significantly affects plant morphology, often reducing leaf size, altering leaf dimensions, and decreasing photosynthetic capacity while modifying internal water transport mechanisms (Bhusal et al., 2019 ). The study by Pita-Barbosa et al. ( 2023 ) identified several drought tolerance mechanisms in Eucalyptus , including improved water-use efficiency, stomatal regulation, and increased resistance to xylem embolism. These species also develop deep root systems to access groundwater and produce osmoprotective compounds to maintain cellular turgor. Combined with foliar adaptations, these traits enable Eucalyptus to survive and function efficiently under arid conditions. Drought-tolerant plants generally adapt through deep rooting systems, leaf rolling, hormonal signaling, and efficient transpiration control (Serrano & Peñuelas, 2005; Shahzad et al., 2016 ). López et al. ( 2009 ) evaluated short-term drought resistance in Pinus canariensis seedlings from five geographic origins and found that osmotic adjustment and root-to-shoot ratio acclimation to water deficit were indicative of drought tolerance. These traits were proposed as reliable early predictors of drought resistance under natural conditions. Furthermore, López et al. ( 2020 ) demonstrated that coordination between stem and leaf hydraulic traits defines distinct drought resistance strategies among Fagus sylvatica , Pinus sylvestris , and Sorbus torminalis . Their results showed that each species adopts a unique strategy based on the balance between stem and leaf hydraulics—for instance, Fagus sylvatica exhibits high vulnerability to embolism, whereas Pinus sylvestris follows a more conservative water-use strategy. Similarly, Rodríguez-Gamir et al. ( 2021 ) reported that hydraulic and leaf traits play a crucial role in the survival and recovery of Pinus halepensis seedlings under severe drought. Together, these studies highlight the importance of hydraulic resilience and leaf acclimation in ensuring plant survival under water stress. Morphological and physiological acclimation mechanisms—such as osmotic adjustment and hydraulic coordination—are therefore fundamental for plant persistence in increasingly arid environments. Tree susceptibility to water stress is highly species-dependent (Ryan, 2011), and Eucalyptus species are no exception (Merchant et al., 2007). They are predicted to be particularly vulnerable to future climate change (Booth et al., 2013; James et al., 2016 ; Gonçalves et al., 2017 ; Bosi, 2020). Eucalyptus is among the most widely cultivated genera globally, comprising over 700 species. Although renowned for their tolerance to aridity, Eucalyptus species display significant inter- and intra-specific variability in this trait (Merchant et al., 2006; Shvaleva et al., 2006; Merchant et al., 2010; Warren et al., 2011). Consequently, morphological and physiological traits associated with drought responses vary considerably among populations and even within the same species (Merchant et al., 2007; Correia et al., 2014 ; McKiernan et al., 2014, 2016; Costa et al., 2017). This variability is partly explained by the high genetic diversity and extensive outbreeding characteristic of Eucalyptus (Boland et al., 2006 ), combined with the strong influence of edaphic and climatic factors on species distribution (White et al., 2000). As a result, Eucalyptus species form close ecological associations with their environments, leading to considerable physiological variation across different climatic zones—variation that remains insufficiently characterized (White et al., 2000). In Tunisia, studies on the physiological responses of Eucalyptus to water deficit remain limited (Souden et al., 2020). Given the expected intensification of drought and the extensive use of Eucalyptus in regions with scarce water resources, identifying drought-tolerant species is essential for maintaining and improving forest productivity. Therefore, the primary objective of this study was to evaluate the morpho-physiological responses of three melliferous Eucalyptus species ( E. camaldulensis , E. maculata , and E. paniculata ) under varying water availability conditions. These species were tested in two distinct bioclimatic zones: the humid bioclimate of Sejnane and the sub-humid bioclimate of Rimel in northeastern Tunisia. The study aimed to assess the drought resilience of these species and identify reliable criteria for selecting drought-resistant Eucalyptus species. It was hypothesized that Eucalyptus species exhibit differing levels of morpho-physiological adaptability to water stress and that certain species may be more suitable for reforestation programs in water-limited environments. 2. Materials and Methods 2.1. Study sites The study sites are located in Rimel and Sejnane arboreta (Bizerte Government-North Tunisia) under sub-humid and humid bioclimates, respectively. Both arboreta were set up in 1964. Geographical coordinates and climatic characteristics of study sites are summarized in Table 1 . At both sites, prospecting and harvesting were carried out at the same day to minimize errors. In Rimel site, soils consist of sandy Quaternary materials overlying continental clays, with hydromorphic conditions and non-calcareous sand layers influencing water retention. In Sejnene site, the soil is primarily composed of Oligocene flysch with dominant clayey and marl facies, which are more prone to erosion, affecting water availability depending on slope and elevation. Table 1 Geographic coordinates and climatic characteristics of the study sites (INM 1974–2019). Site Longitude (N) Latitude (E) Average annual precipitation (mm/year) Mean annual temperature (°C) Bioclimate Rimel 37° 14.0’ 9° 57.00’ 631.38 18.85 Sub-humid Sejnane 37° 8.0’ 9° 7.1’ 936.38 18.77 Humid 2.2. Plant material In each site, three species of Eucalyptus cultivars were studied: E. camaldulensis Dehn. 1832, E. paniculata Sm. 1797, and E. maculata Hook. 1844. Three branches (1 m-long) per species were cut from three separate individuals of each plant species in each site. The branches, oriented from north to south, were selected from the first branches. The plantation was established in 1962/1963. 2.3. Water and Soil parameters According to Emberger's classification, the Rimmel and Sejnane project areas belong to the bioclimatic subhumid and humid stages, with a seasonal distribution of aridity intensity. The climatic characteristics of the two sites are taken from the Institut National de Métérologie (Rimmel and Sejnane) (IMN 1974–2019). The daily reference evapotranspiration (ETo) from 2014 to 2019, was calculated according to Hargreaves–Samani (1985) method using the following equation: ETo = 0.0135 KT.Ra.TD 1/2. (TC + 17.8) Where : • TD = T max-T min (°C) • TC: The average daily temperature (°C) • KT = 0.162 for interior regions (Sejnane site) and KT = 0.19 for coastal regions (Rimel site) • Ra: Extraterritorial radiation (MJ/m2/year) The water balance deficit was calculated as the difference between values of Annual Precipitation (P) and Evapotranspiration (ETo). WBD = P-ETo Where: P: Average monthly precipitation (mm) and ETo: The daily reference evapotranspiration. The soil water content (SWC) for each plant and site was measured manually by the Time Domain Reflectometry (TDR) in soil depth of 20 cm according to Thomsen et al. 2007 . 2.4. Fruits, leaves and twig production In each site and for each Eucalyptus species, the trees were classified based on the fruiting state into two groups; well-fruited trees and poorly-fruited trees. In each group, three trees were randomly chosen for fruit production estimation. All fruits, leaves, and twigs were collected from each branch and weighted in g. The dry Matter (DM) was determined after placing the leaves in an oven at 70°C for 48 hours. Measurement was carried out using a precision balance (0.001g). Results–expressed in grams for fruits and in kg for twigs and leaves (Kg) - were the mean of three replicates. 2.5. Physiological parameters measurement A physiological study was carried out on three twigs collected from the sampled branches for each Eucalyptus species (well fruited and poorly fruited). 2.5.1. Leaf Water potential Leaf water potential measurement (Ψ) of each Eucalyptus species was measured using the pressure chamber technique (Scholander et al. 1965 ; Holbrook et al. 1995 ). Small twigs from harvested branches were collected at pre-dawn (before 6 a.m.), immediately sealed in plastic bags with moist paper towels to prevent water loss, and stored in a portable cooler to maintain temperature and humidity. The samples were transported to the laboratory and analyzed within 1–2 hours after collection to ensure accurate Ψ readings. During the analysis, twigs were placed in a pressure chamber (Arimad 2®, A.R.I, KfarCharuv) fed by a Nitrogen gas cylinder and equipped with a lamp-carrying magnifying glass. 2.2. Gas exchange data Gas exchange was performed using a portable gas-exchange system (LI-6400, Li-CorInc, Lincoln, NE, USA) equipped with 2x3 cm light-source chamber. Prior to measurements, the branches were cut early in the morning, rehydrated by placing the cut ends in water, and kept in a shaded, cool environment to maintain their physiological integrity. Ambient conditions were recorded, the temperature was maintained at 25°C, the humidity of the incoming air was kept at 60% and radiation was fixed at 1500 µmol photons m⁻² s⁻¹. The CO 2 are reserved at 400 µmol CO₂ mol⁻¹ air. After reaching steady-state, measurements of net photosynthesis (An), stomatal conductance (gs) and transpiration (T), were calculated according to Von Caemmerer and Farquhar (1981). Instantaneous Water Use Efficiency (Wuei) was calculated as the ratio between (An) and (gs). 2.5.3. Xylem specific conductivity and the percent loss of conductivity Specific hydraulic conductivity (Ks) was determined using the XYLEM (Embolism Meter, Bronkhorst, Montigny-les-Cormeilles, France). Branches were collected early in the morning, immediately recut under water to avoid xylem embolism, and transported to the laboratory in sealed plastic bags with moist paper towels to prevent desiccation. The samples were stored in a cool environment and processed within a few hours of collection. Before measuring the hydraulic conductivity (Kh), all branch segments were flushed with degassed, filtered water to remove any existing embolisms and ensure maximum conductivity. Kh was calculated as the ratio between the flow rate through each segment and the corresponding hydrostatic pressure gradient. The xylem cross-sectional area was then used to convert Kh into specific hydraulic conductivity (Ks, kg m⁻¹ MPa⁻¹ s⁻¹) following Tyree et al. (2005). The percent loss of conductivity (PLC), reflecting xylem cavitation, was calculated as: PLC (%) = 100*(K max -K i )/K max ) Where: K max : maximal conductivity; K i : initial conductivity; PLC is the percent loss of conductivity due to cavitation. 2.6. Statistical analysis One-way ANOVA was performed for all collected data. Means significant differences were performed using the Newman–Keuls’s tests at p = 0.05 . Statistical analysis was realized using the SAS software. ACP was conducted using SPSS software. All values are presented as the mean of three replications ± standard deviation. 3. Results 3.1. Evapotranspiration, soil water content (SWC), and water balance deficit The analysis of the water balance (P – ETo) from 2014 to 2019 revealed distinct seasonal trends between the two studied bioclimates (Table 2 ). At the sub-humid Rimel site, a water deficit persisted for most of the year, with the most severe deficits occurring from May to August. The maximum monthly deficit reached − 201 mm in July, indicating intense summer water stress. In contrast, the humid Sejnane site exhibited smaller deficits during the same period, with a maximum of − 182 mm in July. Overall, Sejnane experienced a shorter deficit period and a smaller total annual deficit (–147 mm) compared to Rimel (–580 mm), suggesting better water availability throughout the year. The soil water content (SWC) results also confirmed this pattern, showing that the soil at Sejnane was more humid (14.49%) than at Rimel (11.62%) (Table 3 ). Table 2 Precipitation (P), Evapotranspiration (ETo) and the water balance deficit (P-ETo) of the two studied bioclimates (period 2014–2019) Bioclimates Parameters Months Total J F M A M J J A S O N D Sub-humid (Rimel site) P (mm) 100 76 60 20 30 5 3 41 36 89 85 82 627 ETo 30 43 71 107 141 185 201 173 112 72 41 30 1207 P-ETo 70 33 -10 -86 -109 -179 -201 -132 − 75 18 44 52 -580 Humid (Sejnane site) P (mm) 179 135 99 56 25 10 3 7 39 67 129 182 931 ETo 25 35 60 81 123 177 185 166 102 63 33 25 1078 P-ETo 154 100 39 -25 -98 -167 -182 -159 -63 4 96 157 -147 Table 3 Soil Water Content measured in September 2019 Site SWC (%) Rimel 11.62 ± 1.2 Sejnane 14.49 ± 2.1 3.2. Eucalyptus production under two bioclimatic conditions 3.2.1. Fruit production Across both bioclimates (Fig. 1 ), E. maculata and E. paniculata consistently produced the highest fruit yields, with significantly greater production recorded at the humid Sejnane site ( E. maculata : 85 ± 6 g; E. paniculata : 10.46 ± 1.5 g) compared to the sub-humid Rimel site ( E. maculata : 31 ± 0.46 g; E. paniculata : 30 ± 0.73 g). In contrast, E. camaldulensis showed the lowest fruit yield at both sites, with 9.66 ± 1.7 g at Sejnane and 17.66 ± 1.04 g at Rimel. Statistical analysis confirmed significant differences among species and sites (p < 0.05). 3.2.2. Leaf production In the sub-humid bioclimate (Rimel site, Fig. 2 A), well-fruited Eucalyptus individuals exhibited greater leaf biomass compared to poorly fruited plants. Among the three species, E. paniculata recorded the highest average leaf weight (0.0663 ± 0.0035 kg). Conversely, in the humid bioclimate (Sejnane site, Fig. 2 B), E. maculata showed the greatest leaf biomass, followed by E. paniculata and E. camaldulensis . 3.2.3. Twig production Twig biomass followed a similar pattern to that of leaves across both bioclimates (Fig. 3 ). The highest twig weight was observed for E. paniculata at the sub-humid site and for E. maculata at the humid site. Statistical analysis indicated that both site and species significantly influenced twig and leaf production ( p < 0.05 ). 3.3. Physiological performance of Eucalyptus under two bioclimatic conditions 3.3.1. Leaf water potential Statistical analysis revealed that leaf water potential (Ψ) varied significantly with bioclimate, species, and fruit production (p < 0.05). Eucalyptus species cultivated under sub-humid conditions exhibited higher Ψ values (–0.17 ± 0.42 to − 0.39 ± 0.17 MPa) than those grown in humid conditions (–0.23 ± 0.7 to − 0.96 ± 6.3 MPa) (Table 4 ). Poorly fruited individuals generally displayed higher Ψ values than well-fruited ones. The highest Ψ values were recorded for poorly fruited E. camaldulensis at the sub-humid site and well-fruited E. maculata at the humid site. Table 4 Leaf water potential of poorly fruited and well fruited Ecucalyptus camaldulensis, E.maculata and E. paniculata plant species in sub humid (Rimel site) and humid (Sejnane site) bioclimates (September 2019). Plant species Ψ (Mpa) Sub-humid bioclimate (Rimel) Humid bioclimate (Sejnane) E. camaldulensis poorly fruited -0.17 ± 0.42 ab -0.48 ± 2.5 bc E. camalduensis well-fruting -0.19 ± 0.57 ab -0.68 ± 4.9 b E. paniculata poorly fruited -0.27 ± 1.3 b -0.37 ± 1.04 bc E. paniculata well-fruited -0.39 ± 0.17 a -0.96 ± 6.3 a E. maculata poorly fruited -0.23 ± 0.4 ab -0.28 ± 1.02 c E. maculata well fruited -0.25 ± 0.88 ab -0.29 ± 0.7 c Different letters denote significant differences ( p < 0.05 ) 3.3.2. Gas exchange response patterns Gas exchange parameters were significantly affected by bioclimatic conditions, species, and fruit production (p < 0.05). Net photosynthetic rate (Aₙ), stomatal conductance (gₛ), transpiration (Tr), and intrinsic water-use efficiency (WUEi) were significantly higher in all species grown under humid conditions and in well-fruited plants compared to poorly fruited ones (Table 5 ). These parameters declined markedly under sub-humid conditions. Among species, E. paniculata exhibited the highest physiological performance in both bioclimates, whereas E. maculata showed the lowest. Table 5 Net photosynthesis (An), stomatal conductance(gs), transpiration (Tr) and Water Use Efficiency (Wuei) of poorly fruited and well fruited Ecucalyptus camaldulensis, E.maculata and E. paniculata plant species in sub humid (Rimel site) and humid (Sejnane site) bioclimates. Species An (µmol m − 2 s − 1 ) Gs (mol.m − 2 s − 2 ) Tr (mol. m − 2 . s − 2 ) WUEi (µmolCO2. mol − 1 H2O) Humid bioclimate (Sejnane site) E. paniculata poorly fruited 5.021 ± 0.69 ab 0.079 ± 0.004 ab 1.018 ± 0.005 ab 4.895 ± 0.69 ab E. paniculata well-fruting 6.427 ± 0.15 a 0.092 ± 0.001 a 1.020 ± 0.036 ab 6.313 ± 0.58 a E. maculata poorly fruited 3.142 ± 0.46 c 0.070 ± 0.002 ab 1.044 ± 0.160 a 3.009 ± 0.30 d E. maculata well-fruting 3.203 ± 0.52 c 0.077 ± 0.001 ab 1.056 ± 0.000 a 3.033 ± 0.51 d E. camaldulensis poorly fruited 3.693 ± 0.12 abc 0.033 ± 0.002 c 0.925 ± 0.017 c 3.991 ± 0.57 c E. camaldulensis well-fruiting 4.773 ± 0,38 ab 0.034 ± 0.004 c 1.055 ± 0.114 a 4.524 ± 0.88 ab Sub-humid bioclimate (Rimel site) E. paniculata poorly fruited 3.27 ± 0.20 ab 0.045 ± 0.004 a 0.812 ± 0.044 c 4.03 ± 0.27 a E. paniculata well-fruited 3.45 ± 0.31 a 0.048 ± 0.005 a 0.927 ± 0.164 b 3.73 ± 0.55 ab E. maculata poorly fruited 2.22 ± 0.21 c 0.032 ± 0.005 ab 1.017 ± 0.017 a 2.182 ± 0.20 d E. maculata well-fruited 2.88 ± 0.13 ab 0.039 ± 0.004 ab 1.019 ± 0.026 a 2.826 ± 0.21 c E. camaldulensis poorly fruited 2.94 ± 0.27 ab 0.020 ± 0.003 c 0.739 ± 0.295 c 3.978 ± 0.13 ab E. camaldulensis well-fruited 3.24 ± 0.22 ab 0.025 ± 0.015 c 0.800 ± 0.208 cd 4.050 ± 0.31 a Different letters denote significant differences ( p < 0.05 ) 3.3.3. Variation in hydraulic traits Xylem-specific conductivity (Kₛ) and percentage loss of conductivity (PLC) varied significantly among species, bioclimates, and fruiting levels ( p < 0.05 ) (Table 6 ). Kₛ values were generally higher at the Rimel site (sub-humid) than at Sejnane (humid), whereas PLC values showed the opposite trend. Well-fruited plants displayed lower Kₛ and higher PLC values under both bioclimates. Notably, heavily fruiting E. paniculata individuals exhibited the lowest Kₛ and PLC values across both sites, suggesting higher hydraulic regulation under reproductive stress. Table 6 Xylem specific conductivity (KS) and the percent loss of conductivity (PLC %) of poorly fruited and well fruited’ Eucalyptus camaldulensis, E. maculata, E. paniculata plant species in sub humid (Rimel site) and humid (Sejnane site) bioclimates. Species KS (Kg.m − 1 .MPa − 1 .s − 1 ) PLC (%) Humid (Sejnane site) E. paniculata poorly fruited 0.7399 ± 0.0519 a 26.3 ± 0.73 d E. paniculata well-fruited 0.0654 ± 0.084 c 33.4 ± 0.86 c E. maculata poorly fruited 0.7509 ± 0.0877 a 55.98 ± 0.26 abc E. maculata well-fruited 0.0916 ± 0.0108 b 59.64 ± 0.10 ab E. camalendensis poorly fruited 0.682 ± 0.0906 a 55.37 ± 0.19 abc E. camalendensis well-fruited 0.0978 ± 0.0012 b 63.87 ± 1.18 a Sub-Humid (Rimel site) E. paniculata poorly fruited 0.043 ± 0.0056 a 66.4 ± 0.25 c E. paniculata well-fruited 0.0315 ± 0.0033 b 74.65 ± 0.37 ab E. maculata poorly fruited 0.0503 ± 0.0027 a 75.15 ± 0.72 ab E. maculata well-fruited 0.0094 ± 0.0061 c 89.76 ± 1.18 b E. camalendensis poorly fruited 0.0191 ± 0.00245 b 96.174 ± 0.10 a E. camalendensis well-fruited 0.005919 ± 0.0008 c 97.74 ± 0.23 a Different letters denote significant differences (p < 0.05) 3.4. Correlations among analyzed variables Correlation analysis (Fig. 4 ) revealed a positive and significant relationship between fruit production (FP), xylem conductivity (Kₛ), transpiration (Tr), and stomatal conductance (gₛ). Leaf production (LP) was positively correlated with net photosynthesis (Aₙ), relationships that characterized the humid bioclimate. In contrast, hydraulic parameters (Ψ, PLC, WUEi) showed strong positive intercorrelations under sub-humid conditions, distinguishing Eucalyptus responses in this bioclimate. 4. Discussion The growing frequency and intensity of droughts, resulting from altered precipitation regimes, represent a major threat to tropical and subtropical forest ecosystems (Zhou et al., 2011; Davidson et al., 2012). Prolonged drought periods can increase tree mortality, reduce forest biomass productivity, and diminish carbon sequestration capacity in natural forests (Chaves et al., 2002; Zhou et al., 2013). Furthermore, Bleby et al. (2012) reported that planted forests tend to be more vulnerable to extreme environmental stress than natural forests, mainly due to their lower ecological resilience. Eucalyptus species play an important ecological and economic role in North Africa, particularly as introduced species used to prevent soil erosion and supply timber (Laclau, 2018 ). In Tunisia, Eucalyptus represents the most widespread hardwood genus, covering approximately 5% of the total national forest area (DGF, 2010). As Tunisia is already below the water stress threshold (Oxford Analytica, 2023), understanding Eucalyptus water requirements and physiological responses to drought is increasingly critical. Water deficit remains the primary threat to Eucalyptus plantations, as this genus generally favors humid environments. Nevertheless, Eucalyptus is extensively used in reforestation programs worldwide (Zerga et al., 2021 ), especially across the southern Mediterranean region, which has experienced intensified drought conditions over recent decades (Lee et al., 2023 ). It is therefore essential to identify taxa that are less vulnerable to abiotic stress, in order to minimize potential impacts of climate change (Booth, 2013 ; Da Silva et al., 2022 ). To better characterize adaptive mechanisms in Eucalyptus , it is important to examine its physiological and morphological responses under contrasting environmental conditions. This macroecological study assessed three Eucalyptus species ( E. paniculata , E. camaldulensis , and E. maculata ) cultivated under two distinct bioclimatic conditions in Tunisia. The results demonstrated that Eucalyptus species grown in the two arboreta—Sejnane (humid) and Rimel (sub-humid)—displayed considerable plasticity and an ability to acclimate and grow outside their native range. Under the humid conditions of Sejnane, all species showed improved growth performance compared to those cultivated at Rimel. Similar patterns have been reported by several authors, who observed increased biomass accumulation under wetter conditions (Ghannoum et al., 2010; Dieleman et al., 2012 ; Pagotto et al., 2025 ; Way, 2013). Among the studied taxa, E. paniculata exhibited the highest productivity and physiological performance, outperforming E. camaldulensis and E. maculata under humid conditions. Nonetheless, all three species maintained satisfactory physiological performance under the more stressful sub-humid conditions of Rimel, demonstrating a certain degree of resilience. According to Argus et al. ( 2015 ), E. camaldulensis typically shows low stomatal conductance (gₛ) as an adaptive mechanism for water conservation. Other studies indicate that Eucalyptus species combine morphological and physiological adjustments to cope with drought stress (García et al., 2023 ). For instance, E. camaldulensis seedlings from semi-arid Australia develop extensive adventitious roots, increased stem porosity, and hypertrophy to improve water uptake and storage (Gibson, 1995; Zhang et al., 2021 ). Leaf morphological adjustments and variations among Eucalyptus species have also been linked to bioclimatic conditions (Bustamante et al., 2021 ). The physiological capacities observed in this study largely depended on environmental conditions, especially soil moisture and water balance, which regulate foliage activity and photosynthetic efficiency (Oren et al., 1999 ; Shao et al., 2024 ). Moreover, fruiting performance correlated positively with hydraulic traits such as stomatal conductance, transpiration, and xylem conductivity. These relationships support the approach proposed by Shani et al. ( 2025 ), which emphasizes the use of physiological parameters as reliable indicators for selecting drought-tolerant genotypes. Our results showed that plants grown under the sub-humid conditions of Rimel experienced reduced gas exchange, consistent with previous findings for E. grandis , E. urophylla , E. camaldulensis , E. torelliana , and E. phaeotrica under water stress (Lima et al., 2003 ; Shang et al., 2016). At Rimel, Eucalyptus species also exhibited high vulnerability to cavitation, as indicated by elevated PLC values and strongly negative water potentials. This vulnerability was accompanied by a simultaneous decline in xylem-specific conductivity, underscoring the close link between hydraulic function and soil water availability. Similar results were reported by Shang et al. (2016) and Liu et al. ( 2021 ) in E. urophylla plantations under periodic drought. The observed decline in intrinsic water-use efficiency (WUEi) under high water stress conditions likely reflects increased physiological constraints on carbon assimilation. Butler et al. ( 2022 ) emphasized the importance of water potential as a diagnostic measure of plant water status, noting that reduced soil water potential leads to lower leaf water potential, decreased stomatal conductance, and reduced photosynthetic rates. This cascade effect ultimately limits chlorophyll content and light absorption capacity (Bhusal et al., 2023 ). Beyond the implications for Eucalyptus plantations, these findings contribute to the broader understanding of forest adaptation strategies in regions experiencing rising aridity (Dry, 2013). As drought events become more frequent and severe globally, developing a deeper understanding of species-specific physiological responses is essential for guiding reforestation programs, maintaining forest productivity, and enhancing ecosystem resilience in the face of climate change. 6. Conclusion This study highlights the importance of understanding species-specific responses of Eucalyptus to changing climatic conditions, particularly under increasing water scarcity. The results demonstrate significant variability in physiological performance among species and sites, underscoring the adaptive capacity and ecological plasticity of this genus. The Sejnane provenance, thriving under humid conditions, exhibited superior physiological tolerance to drought compared with the Rimel provenance, adapted to sub-humid environments. These differences emphasize the importance of selecting Eucalyptus species and provenances based on their climatic adaptability to optimize reforestation success in water-limited regions. Among the species examined, E. paniculata showed a strong ability to acclimate across contrasting edaphoclimatic conditions, maintaining efficient water use and physiological performance under stress. This adaptability positions E. paniculata as a promising candidate for future reforestation and afforestation programs in areas facing recurrent drought. Overall, the study provides valuable insights into the morpho-physiological mechanisms underlying drought tolerance in Eucalyptus , offering practical guidance for species selection and forest management under current and future climate change scenarios. By integrating such adaptive traits into reforestation planning, it is possible to enhance forest resilience, ensure sustainable productivity, and support ecosystem restoration efforts in arid and semi-arid regions. Declarations Author contributions S.F. conceptualized the study and prepared the initial draft of the manuscript. A.S. supervised the overall work, contributed to the critical review, and provided major revisions to improve the scientific quality. Y.Y. contributed to the literature collection, data organization, and figure preparation. FY participated in data curation, formatting, and manuscript editing. W. E. and H.B. assisted in conceptualization and validation of scientific content and contributed to the final proofreading and formatting of references. All authors read and approved the final version of the manuscript. Data Availability Statement The data supporting the findings of this study are available from the corresponding author upon reasonable request. Ethical Statement Not applicable Declaration of Competing Interest The authors declare that they have no competing financial interests or personal relationships that could have influenced the work reported in this paper. Funding statement This work was supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University (IMSIU) (grant number IMSIU-DDRSP2601). References Argus RE, Colmer TD, Grierson PF (2015) Physiological flood tolerance and recovery. Plant Cell Environ 38:1189–1199. https://doi.org/10.1111/pce.12473 Bhusal N, Han SG, Yoon TM (2019) Impact of drought stress on photosynthetic response, leaf water potential, and stem sap flow in two cultivars of bi-leader apple trees (Malus× domestica Borkh). Sci Hort 246:535–543. 10.1016/j.scienta.2018.11.021 Bhusal N, Park I, Jeong H, Choi S, Han BH, Yoon SG TM (2023) Photosynthetic traits and plant hydraulic dynamics in Gamhong apple cultivar under drought, waterlogging, and stress recovery periods. Sci Hort 321:112276 Boland DJ, Brooker MIH, Chippendale GM, Hall N, Hyland BP, Johnston RD, Turner JD (eds) (2006) For trees Aust. CSIRO publishing Booth TH (2013) Eucalypt plantations and climate change. Ecol Manag 301:28–34 Bosi C, Pezzopane JRM, Sentelhas PC (2020) Silvopastoral system with Eucalyptus as a strategy for mitigating the effects of climate change on Brazilian pasturelands. Acad Bras Cienc 92. https://doi.org/10.1590/0001-3765202020180425 Bullock SH (1986) Climate of Chamela, Jalisco, and trends in the south coastal region of Mexico. Arch Met Geophys Bioclimatol B 36:297–316. https://doi.org/10.1007/BF02263135 Bustamante M, Santos GM, Lemos-Filho JP, Almeida JPN (2021) Adaptive plasticity in leaf traits of Eucalyptus grandis along a climate gradient. Ecol Manag 479:118611. https://doi.org/10.1016/j.foreco.2020.118611 Butler JB, Harrison PA, Vaillancourt RE, Steane DA, Tibbits JFG, Potts BM (2022) Climate Adaptation, Drought Susceptibility, and Genomic-Informed Predictions of Future Climate Refugia for the Australian Forest Tree Eucalyptus globulus . Forests 13:575. https://doi.org/10.3390/f13040575 Correia B, Pintó-Marijuan M, Neves L, Brossa R, Dias MC, Costa A, Pinto G (2014) Water stress and recovery in the performance of two Eucalyptus globulus clones: physiological and biochemical profiles. Physiol Plant 150(4):580–592. https://doi.org/10.1111/ppl.12110 Costa DD, da Silva Pereira TA, Fragoso CR Jr, Madani K, Uvo CB (2016) Understanding drought dynamics during dry season in Eastern Northeast Brazil. Front Earth Sci 4:69. https://doi.org/10.3389/feart.2016.00069 Da Silva PHM, Araujo MJ, Lee DJ et al (2022) Adaptability and stability of novel eucalypt species and provenances across environments in Brazil at two assessment. New Forest 53:779–796. https://doi.org/10.1007/s11056-021-09886-7 De Moraes DHM, Mesquita M, Graciano-Ribeiro D, de Araújo DS, Battisti R, Flores RA, Casaroli D (2022) The effect of xylem vessel diameter on potential hydraulic conductivity in different rice stem longitudinal positions. Flora 295:152147. https://doi.org/10.1016/j.flora.2022.152147 Dieleman WI, Vicca S, Dijkstra FA, Hagedorn F, Hovenden MJ, Larsen KS, … and, Janssens IA (2012) Simple additive effects are rare: a quantitative review of plant biomass and soil process responses to combined manipulations of CO2 and temperature. Glob chang biol 18(9):2681–2693. https://doi.org/10.5902/198050981829 Dye P (2013) A review of changing perspectives on Eucalyptus water-use in South Africa. Ecol Manag 301:51–57. https://doi.org/10.1016/j.foreco.2012.08.027 García LY, Rubilar R, Valverde JC, Emhart V, Bascuñán L, Medina A, Bozo D (2023) Morphological, physiological and carbon balance response of Eucalyptus genotypes under water stress. New Forest 1–17. https://doi.org/10.1007/s11056-023-09985-7 Ghannoum O, Way DA (2011) On the role of ecological adaptation and geographic distribution in the response of trees to climate change. Tree Physiol 31(12):1273–1276. https://doi.org/10.1093/treephys/tpr115 Gibson A, Bachelard EP, Hubick KT (1995) Relationship between climate and provenance variation in Eucalyptus camaldulensis Dehnh. Funct Plant Biol 22(3):453–460. https://doi.org/10.1071/PP9950453 Gonçalves JL, Alvares C, Rocha JH, Brandani CB, Hakamada R (2017) Eucalypt plantation management in regions with water stress. South For: J Sci 79(3):169–183. https://doi.org/10.2989/20702620.2016.1255415 Guarnaschelli AB, Garau AM, Lemcoff JH (2012) Water stress and afforestation: a contribution to ameliorate forest seedling performance during the establishment. Water stress 2:74–110 Héroult A, LIN YS, Bourne A, Medlyn BE, Ellsworth DS (2013) Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought. Plant Cell Env 36(2):262–274. https://doi.org/10.1111/j.1365-3040.2012.02570.x Holbrook NM, Burns MJ, Field CB (1995) Negative xylem pressures in plants: a test of the balancing pressure technique. Science 270(5239):1193–1194. https://10.1126/science.270.5239.11 Holbrook NM, Burns MJ, Field CB (1995) Negative xylem pressures in plants: a test of the balancing pressure technique. Science 270(5239):1193–1194. https://10.1126/science.270.5239.11 Huante P, Rincón E (1997) Responses to light changes in tropical deciduous woody seedlings with contrasting growth rates. Oecologia 113:53–66. https://doi.org/10.1007/s004420050353 James C, Reid M, Capon S (2016) Climate change and the future of Australian riverine vegetation. Vegetation of Australian Riverine landscapes. Biol Ecol manag. 387–405 Laclau JP (2018) Managing Eucalyptus Plantations under Global Changes, IUFRO, Ed. Montpellier: Le Corum, France, 2018 Lee H, Calvin K, Dasgupta D, Krinmer G, Mukherji A, Thorne P, Zommers Z (2023) Synthesis report of the IPCC Sixth Assessment Report (AR6), Longer report. IPCC Lewis JD, Phillips NG, Logan BA, Hricko CR, Tissue DT (2011) Leaf photosynthesis, respiration and stomatal conductance in six Eucalyptus species native to mesic and xeric environments growing in a common garden. Tree Physiol 31(9):997–1006. https://doi.org/10.1093/treephys/tpr087 Lima WDP, Jarvis P, Rhizopoulou S (2003) Stomatal responses of Eucalyptus species to elevated CO2 concentration and drought stress. Sci Agricol 60:231–238. https://doi.org/10.1590/S0103-90162003000200005 Liu X, Wang N, Cui R, Song H, Wang F, Sun X, Du N, Wang H, Wang R (2021) Quantifying key points of hydraulic vulnerability curves from drought-rewatering experiment using differential method. Front Plant Sci 12:627403. https://doi.org/10.3389/fpls.2021.627403 López R, Cano FJ, Choat B, Cochard H, Gil L (2020) Coordination of stem and leaf traits define different strategies to face drought in European beech, Scots pine and wild service tree. Tree Physiol 40(2):164–175. https://doi.org/10.1093/treephys/tpz114 López R, Rodríguez-Calcerrada J, Gil L (2009) Physiological and morphological response to water deficit in seedlings of five provenances of Pinus canariensis : potential to detect variation in drought-tolerance. Trees 23:509–519. https://doi.org/10.1007/s00468-008-0297-5 Oren R et al (1999) Survey and synthesis of intra and interspecific variation in stomatal sensitivity to vapour pressure deficit. Plant Cell Env 22:1515–1526. https://doi.org/10.1046/j.1365-3040.1999.00513.x Pagotto MA, Aragão JRV, Hornink B, Menezes IRN, Tomazello-Filho M, Lisi CS, Leal IR, Tabarelli M (2025) Biomass production by tree species is negatively affected by decreased precipitation and chronic anthropogenic disturbance in a Caatinga dry forest. J Arid Environ 228 Article 105340. https://doi.org/10.1016/j.jaridenv.2025.105340 Pita-Barbosa A, Oliveira LA, De Barros NF, Hodecker BER, Oliveira FS, Araújo WL, Martins SC (2023) Developing a Roadmap to Define a Potential Ideotype for Drought Tolerance in Eucalyptus . Sci 69(1):101–114. https://doi.org/10.1093/forsci/fxac044 Rodríguez-Gamir J, Sancho-Knapik D, Peguero-Pina JJ, Gil-Pelegrín E (2021) Hydraulic traits and leaf responses in Pinus halepensis seedlings under severe drought conditions and recovery. Ecol Manag 492:119191 Scholander PF, Bradstreet ED, Hemmingsen EA, Hammel HT (1965) Sap Pressure in Vascular Plants: Negative hydrostatic pressure can be measured in plants. Science 148(3668):339–346. https://doi.org/10.1126/science.148.3668.3 Serrano L, Penuelas J (2005) Contribution of physiological and morphological adjustments to drought resistance in two Mediterranean tree species. Biol Plant 49:551–559. https://doi.org/10.1007/s10535-005-0049-y Shahzad MA et al (2016) Drought stress and morphophysiological responses in plants. Water stress and crop plants: A sustainable approach. 2: 452–467. https://doi.org/10.1002/9781119054450.ch27 Shani MY, Ditta A, Khan MKR, Rasheed A, Azhar MT, Khan AS (2025) Deciphering drought tolerance in cotton genotypes through integrated morpho-physiological and biochemical markers at flowering stage. Sci Rep 15:44123. https://doi.org/10.1038/s41598-025-28237-6 Shao S, Li G, Wang J, Wang Y, Qu M, Zhao H, Zhu W, Li J (2024) Temperature and soil attributes drive the regional variation in leaf anatomical traits of Populus euphratica. Global Ecol Conserv 54:e03107. https://doi.org/10.1016/j.gecco.2024.e03107 Thomsen A, Schelde K, Drøscher P (2007) Mobile TDR for geo-referenced measurement of soil water content and electrical conductivity. Prec Agricul 8:213–223. https://doi.org/10.1007/s11119-007-9041-1 White DA, Beadle CL, Sands PJ, Worledge D, Honeysett JL (1999) Quantifying the effect of cumulative water stress on stomatal conductance of Eucalyptus globulus and Eucalyptus nitens: a phenomenological approach. Funct Plant Biol 26:17–27. https://doi.org/10.1071/PP98023 Zerga B, Warkineh B, Teketay D, Egner B (2021) The sustainability of reforesting landscapes with exotic species: A case study of eucalypts in Ethiopia. Sustainability: Sci Pract Policy 4., Article 5. https://doi.org/10.1186/s42055-021-00044-7 Zhang J, Li X, Cui Y, Zhang C (2021) Plant physiological responses to drought stress and their management strategies in agriculture. Plants 10(4):687. https://doi.org/10.3390/plants10040687 Zhang Z, Zhao P, McCarthy HR, Ouyang L, Niu J, Zhu L et al (2016) Hydraulic balance of a Eucalyptus urophylla plantation in response to periodic drought in low subtropical China. Front Plant Sci 7:1346. https://doi.org/10.3389/fpls.2016.01346 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 02 Feb, 2026 Editor assigned by journal 09 Jan, 2026 First submitted to journal 08 Jan, 2026 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-8554718","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":584201649,"identity":"709dcc18-6982-433a-892c-2e1c93f254f7","order_by":0,"name":"Sondes Fkiri","email":"","orcid":"","institution":"National Institute of Research in Rural Engineering Water and Forests: Institut National de Recherche en Genie Rural Eaux et Forets","correspondingAuthor":false,"prefix":"","firstName":"Sondes","middleName":"","lastName":"Fkiri","suffix":""},{"id":584201650,"identity":"866844ce-1ce6-4117-9752-42192f057312","order_by":1,"name":"Awatef Slama","email":"","orcid":"","institution":"National Institute of Research in Rural Engineering Water and Forests: Institut National de Recherche en Genie Rural Eaux et Forets","correspondingAuthor":false,"prefix":"","firstName":"Awatef","middleName":"","lastName":"Slama","suffix":""},{"id":584201651,"identity":"fd737592-d79f-4ea6-bde4-6acd77f079d2","order_by":2,"name":"Fadwa Yahya","email":"","orcid":"","institution":"Prince Sattam bin Abdulaziz University College of Computer Science and Engineering","correspondingAuthor":false,"prefix":"","firstName":"Fadwa","middleName":"","lastName":"Yahya","suffix":""},{"id":584201652,"identity":"e1c52a3f-2ce2-4b80-b520-46d9eea0173c","order_by":3,"name":"Yassine Yahia","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIiWNgGAWjYFACHoYDEAZjAwNDBZBmZm4gRcsZkBZGwloQgLENphcPMDh+9uCBHwyH5eX7D7c9+DivNpq/HajlR8U23FrO5CUc7GE4bLjhRmK74cxtx3NnHGZsYOw5cxu3lgM5Bgd4GA4zbpBgbJPm3XYstwGohZmxDY+W828MDv5hOGw/v/9gm/TfOcdy5xPUciPH4DDQlsSGA4lt0owNNbkbCGmRvPHG4LCMQXoy0C9tkj3HDuRuBGo5iM8vfOdzjD++qbC2nd9//JnEj5q63HnnDx988KMCtxaFA2DnNcP4h8HkAZzqgUC+AUzVwfh1uBSOglEwCkbBCAYAhP9k0+xOkcwAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-1088-3287","institution":"Institut des Regions Arides de Medenine: Institut des Regions Arides","correspondingAuthor":true,"prefix":"","firstName":"Yassine","middleName":"","lastName":"Yahia","suffix":""},{"id":584201653,"identity":"f40e6d4c-478f-4f78-a63f-ab006b89c05d","order_by":4,"name":"Hamdi Bendif","email":"","orcid":"","institution":"Imam Muhammad bin Saud Islamic University: Imam Muhammad Ibn Saud Islamic University","correspondingAuthor":false,"prefix":"","firstName":"Hamdi","middleName":"","lastName":"Bendif","suffix":""},{"id":584201654,"identity":"687bd515-1862-4149-bcfb-a9f0512d7a90","order_by":5,"name":"Walid Elfalleh","email":"","orcid":"","institution":"Imam Muhammad bin Saud Islamic University: Imam Muhammad Ibn Saud Islamic University","correspondingAuthor":false,"prefix":"","firstName":"Walid","middleName":"","lastName":"Elfalleh","suffix":""}],"badges":[],"createdAt":"2026-01-08 19:39:47","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8554718/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8554718/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101881834,"identity":"94aac6b2-c2e2-45d7-8545-757729c9f66f","added_by":"auto","created_at":"2026-02-04 15:16:57","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":236625,"visible":true,"origin":"","legend":"\u003cp\u003eFruits production of poorly fruited and well fruited of three branches/species (1m-long), oriented from north to south, collected from three \u003cem\u003eEucalyptus\u003c/em\u003e sp. (\u003cem\u003eE. camaldulensis, E.maculata, E. paniculata) \u003c/em\u003egrowing in Sub-humid bioclimate (Rimel site) (\u003cstrong\u003eA\u003c/strong\u003e) and humid bioclimate (Sejnane\u003cem\u003e \u003c/em\u003esite) (\u003cstrong\u003eB\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8554718/v1/17949fd984595c7c1dab7ab1.jpeg"},{"id":101852219,"identity":"3903b57b-f1b3-4f76-9ea4-2f72a4e3d503","added_by":"auto","created_at":"2026-02-04 10:11:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":109828,"visible":true,"origin":"","legend":"\u003cp\u003eLeaves weight of poorly fruited and well fruited of three branches/species (1m-long), oriented from north to south, collected from three \u003cem\u003eEucalyptus\u003c/em\u003e sp. (\u003cem\u003eE. camaldulensis, E.maculata, E. paniculata) \u003c/em\u003egrowing in Sub-humid bioclimate (Rimel site) (\u003cstrong\u003eA\u003c/strong\u003e) and humid bioclimate (Sejnane\u003cem\u003e \u003c/em\u003esite) (\u003cstrong\u003eB\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8554718/v1/38208c84b4eb7123709ffdbb.png"},{"id":101881748,"identity":"0d69dacc-5bd8-4b26-999a-ce8036b0c085","added_by":"auto","created_at":"2026-02-04 15:16:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":104390,"visible":true,"origin":"","legend":"\u003cp\u003eTwigs weight of poorly fruited and well fruited of three branches/species (1m-long), oriented from north to south, collected from three \u003cem\u003eEucalyptus\u003c/em\u003e sp. (\u003cem\u003eE. camaldulensis, E.maculata, E. paniculata) \u003c/em\u003egrowing in Sub-humid bioclimate (Rimel site) (\u003cstrong\u003eA\u003c/strong\u003e) and humid bioclimate (Sejnane\u003cem\u003e \u003c/em\u003esite) (\u003cstrong\u003eB\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8554718/v1/0493b0a00101c31782e18baa.png"},{"id":101852238,"identity":"63a99181-9033-4d82-838a-77124ae6bd30","added_by":"auto","created_at":"2026-02-04 10:11:33","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":149305,"visible":true,"origin":"","legend":"\u003cp\u003ePrincipal Component Analysis (PCA) of physiological parameters and \u003cem\u003eEucalyptus\u003c/em\u003e species fruits, leaves, and twigs production under two bioclimates. The circular plot (A) shows the correlation between variables and the diagram (B) shows the bioclimates (HB: Humid; SB: Sub-humid).\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8554718/v1/5320e37bd15e52bdf7db6cec.jpeg"},{"id":101883734,"identity":"01ec83ba-2342-430f-a2ac-0a770684cd99","added_by":"auto","created_at":"2026-02-04 15:29:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1738715,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8554718/v1/d0f11083-0c87-4fd6-9688-b9e3ae958861.pdf"}],"financialInterests":"","formattedTitle":"Differential Adaptation of Eucalyptus Species through Morpho-physiological and Hydraulic Adjustments to Climate Variability","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn recent years, global warming and climate change have become central topics of concern for environmentalists worldwide. Forests\u0026mdash;like all natural ecosystems\u0026mdash;are increasingly exposed to these climatic shifts. Developing effective forest management strategies is therefore essential for selecting superior forest reproductive material and improving plantation performance under changing climate scenarios (Guarnaschelli et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Under such circumstances, forest productivity can only be sustained by selecting species with greater tolerance to low water availability (Linder, 2000; Villar et al., 2011; Correia et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). To minimize the negative effects of climate change on plant communities, particularly forests, it is crucial to protect, maintain, and enhance forest ecosystems while promoting their capacity for carbon sequestration.\u003c/p\u003e \u003cp\u003eClimate change significantly affects plant morphology, often reducing leaf size, altering leaf dimensions, and decreasing photosynthetic capacity while modifying internal water transport mechanisms (Bhusal et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The study by Pita-Barbosa et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) identified several drought tolerance mechanisms in \u003cem\u003eEucalyptus\u003c/em\u003e, including improved water-use efficiency, stomatal regulation, and increased resistance to xylem embolism. These species also develop deep root systems to access groundwater and produce osmoprotective compounds to maintain cellular turgor. Combined with foliar adaptations, these traits enable \u003cem\u003eEucalyptus\u003c/em\u003e to survive and function efficiently under arid conditions. Drought-tolerant plants generally adapt through deep rooting systems, leaf rolling, hormonal signaling, and efficient transpiration control (Serrano \u0026amp; Pe\u0026ntilde;uelas, 2005; Shahzad et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). L\u0026oacute;pez et al. (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) evaluated short-term drought resistance in \u003cem\u003ePinus canariensis\u003c/em\u003e seedlings from five geographic origins and found that osmotic adjustment and root-to-shoot ratio acclimation to water deficit were indicative of drought tolerance. These traits were proposed as reliable early predictors of drought resistance under natural conditions.\u003c/p\u003e \u003cp\u003eFurthermore, L\u0026oacute;pez et al. (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) demonstrated that coordination between stem and leaf hydraulic traits defines distinct drought resistance strategies among \u003cem\u003eFagus sylvatica\u003c/em\u003e, \u003cem\u003ePinus sylvestris\u003c/em\u003e, and \u003cem\u003eSorbus torminalis\u003c/em\u003e. Their results showed that each species adopts a unique strategy based on the balance between stem and leaf hydraulics\u0026mdash;for instance, \u003cem\u003eFagus sylvatica\u003c/em\u003e exhibits high vulnerability to embolism, whereas \u003cem\u003ePinus sylvestris\u003c/em\u003e follows a more conservative water-use strategy. Similarly, Rodr\u0026iacute;guez-Gamir et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) reported that hydraulic and leaf traits play a crucial role in the survival and recovery of \u003cem\u003ePinus halepensis\u003c/em\u003e seedlings under severe drought. Together, these studies highlight the importance of hydraulic resilience and leaf acclimation in ensuring plant survival under water stress. Morphological and physiological acclimation mechanisms\u0026mdash;such as osmotic adjustment and hydraulic coordination\u0026mdash;are therefore fundamental for plant persistence in increasingly arid environments.\u003c/p\u003e \u003cp\u003eTree susceptibility to water stress is highly species-dependent (Ryan, 2011), and \u003cem\u003eEucalyptus\u003c/em\u003e species are no exception (Merchant et al., 2007). They are predicted to be particularly vulnerable to future climate change (Booth et al., 2013; James et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Gon\u0026ccedil;alves et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Bosi, 2020). \u003cem\u003eEucalyptus\u003c/em\u003e is among the most widely cultivated genera globally, comprising over 700 species. Although renowned for their tolerance to aridity, \u003cem\u003eEucalyptus\u003c/em\u003e species display significant inter- and intra-specific variability in this trait (Merchant et al., 2006; Shvaleva et al., 2006; Merchant et al., 2010; Warren et al., 2011). Consequently, morphological and physiological traits associated with drought responses vary considerably among populations and even within the same species (Merchant et al., 2007; Correia et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; McKiernan et al., 2014, 2016; Costa et al., 2017).\u003c/p\u003e \u003cp\u003eThis variability is partly explained by the high genetic diversity and extensive outbreeding characteristic of \u003cem\u003eEucalyptus\u003c/em\u003e (Boland et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2006\u003c/span\u003e), combined with the strong influence of edaphic and climatic factors on species distribution (White et al., 2000). As a result, \u003cem\u003eEucalyptus\u003c/em\u003e species form close ecological associations with their environments, leading to considerable physiological variation across different climatic zones\u0026mdash;variation that remains insufficiently characterized (White et al., 2000). In Tunisia, studies on the physiological responses of \u003cem\u003eEucalyptus\u003c/em\u003e to water deficit remain limited (Souden et al., 2020). Given the expected intensification of drought and the extensive use of \u003cem\u003eEucalyptus\u003c/em\u003e in regions with scarce water resources, identifying drought-tolerant species is essential for maintaining and improving forest productivity.\u003c/p\u003e \u003cp\u003eTherefore, the primary objective of this study was to evaluate the morpho-physiological responses of three melliferous \u003cem\u003eEucalyptus\u003c/em\u003e species (\u003cem\u003eE. camaldulensis\u003c/em\u003e, \u003cem\u003eE. maculata\u003c/em\u003e, and \u003cem\u003eE. paniculata\u003c/em\u003e) under varying water availability conditions. These species were tested in two distinct bioclimatic zones: the humid bioclimate of Sejnane and the sub-humid bioclimate of Rimel in northeastern Tunisia. The study aimed to assess the drought resilience of these species and identify reliable criteria for selecting drought-resistant \u003cem\u003eEucalyptus\u003c/em\u003e species. It was hypothesized that \u003cem\u003eEucalyptus\u003c/em\u003e species exhibit differing levels of morpho-physiological adaptability to water stress and that certain species may be more suitable for reforestation programs in water-limited environments.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Study sites\u003c/h2\u003e \u003cp\u003eThe study sites are located in Rimel and Sejnane arboreta (Bizerte Government-North Tunisia) under sub-humid and humid bioclimates, respectively. Both arboreta were set up in 1964. Geographical coordinates and climatic characteristics of study sites are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. At both sites, prospecting and harvesting were carried out at the same day to minimize errors. In Rimel site, soils consist of sandy Quaternary materials overlying continental clays, with hydromorphic conditions and non-calcareous sand layers influencing water retention. In Sejnene site, the soil is primarily composed of Oligocene flysch with dominant clayey and marl facies, which are more prone to erosion, affecting water availability depending on slope and elevation.\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\u003eGeographic coordinates and climatic characteristics of the study sites (INM 1974\u0026ndash;2019).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLongitude (N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLatitude (E)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAverage annual precipitation (mm/year)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMean annual temperature (\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eBioclimate\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\u003eRimel\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e37\u0026deg; 14.0\u0026rsquo;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9\u0026deg; 57.00\u0026rsquo;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e631.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSub-humid\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSejnane\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e37\u0026deg; 8.0\u0026rsquo;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9\u0026deg; 7.1\u0026rsquo;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e936.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eHumid\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Plant material\u003c/h2\u003e \u003cp\u003eIn each site, three species of Eucalyptus cultivars were studied: \u003cem\u003eE. camaldulensis\u003c/em\u003e Dehn. 1832, \u003cem\u003eE. paniculata\u003c/em\u003e Sm. 1797, and \u003cem\u003eE. maculata\u003c/em\u003e Hook. 1844. Three branches (1 m-long) per species were cut from three separate individuals of each plant species in each site. The branches, oriented from north to south, were selected from the first branches. The plantation was established in 1962/1963.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Water and Soil parameters\u003c/h2\u003e \u003cp\u003eAccording to Emberger's classification, the Rimmel and Sejnane project areas belong to the bioclimatic subhumid and humid stages, with a seasonal distribution of aridity intensity. The climatic characteristics of the two sites are taken from the Institut National de M\u0026eacute;t\u0026eacute;rologie (Rimmel and Sejnane) (IMN 1974\u0026ndash;2019).\u003c/p\u003e \u003cp\u003eThe daily reference evapotranspiration (ETo) from 2014 to 2019, was calculated according to Hargreaves\u0026ndash;Samani (1985) method using the following equation:\u003c/p\u003e \u003cp\u003eETo\u0026thinsp;=\u0026thinsp;0.0135 KT.Ra.TD 1/2. (TC\u0026thinsp;+\u0026thinsp;17.8)\u003c/p\u003e \u003cp\u003eWhere :\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e\u0026bull; TD\u0026thinsp;=\u0026thinsp;T max-T min (\u0026deg;C)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e\u0026bull; TC: The average daily temperature (\u0026deg;C)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e\u0026bull; KT\u0026thinsp;=\u0026thinsp;0.162 for interior regions (Sejnane site) and KT\u0026thinsp;=\u0026thinsp;0.19 for coastal regions (Rimel site)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e\u0026bull; Ra: Extraterritorial radiation (MJ/m2/year)\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe water balance deficit was calculated as the difference between values of Annual Precipitation (P) and Evapotranspiration (ETo).\u003c/p\u003e \u003cp\u003eWBD\u0026thinsp;=\u0026thinsp;P-ETo\u003c/p\u003e \u003cp\u003eWhere: P: Average monthly precipitation (mm) and ETo: The daily reference evapotranspiration.\u003c/p\u003e \u003cp\u003e The soil water content (SWC) for each plant and site was measured manually by the Time Domain Reflectometry (TDR) in soil depth of 20 cm according to Thomsen et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2007\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Fruits, leaves and twig production\u003c/h2\u003e \u003cp\u003eIn each site and for each Eucalyptus species, the trees were classified based on the fruiting state into two groups; well-fruited trees and poorly-fruited trees. In each group, three trees were randomly chosen for fruit production estimation.\u003c/p\u003e \u003cp\u003eAll fruits, leaves, and twigs were collected from each branch and weighted in g. The dry Matter (DM) was determined after placing the leaves in an oven at 70\u0026deg;C for 48 hours. Measurement was carried out using a precision balance (0.001g).\u003c/p\u003e \u003cp\u003eResults\u0026ndash;expressed in grams for fruits and in kg for twigs and leaves (Kg) - were the mean of three replicates.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Physiological parameters measurement\u003c/h2\u003e \u003cp\u003eA physiological study was carried out on three twigs collected from the sampled branches for each Eucalyptus species (well fruited and poorly fruited).\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.5.1. Leaf Water potential\u003c/h2\u003e \u003cp\u003eLeaf water potential measurement (Ψ) of each Eucalyptus species was measured using the pressure chamber technique (Scholander et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1965\u003c/span\u003e; Holbrook et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Small twigs from harvested branches were collected at pre-dawn (before 6 a.m.), immediately sealed in plastic bags with moist paper towels to prevent water loss, and stored in a portable cooler to maintain temperature and humidity. The samples were transported to the laboratory and analyzed within 1\u0026ndash;2 hours after collection to ensure accurate Ψ readings.\u003c/p\u003e \u003cp\u003eDuring the analysis, twigs were placed in a pressure chamber (Arimad 2\u0026reg;, A.R.I, KfarCharuv) fed by a Nitrogen gas cylinder and equipped with a lamp-carrying magnifying glass.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Gas exchange data\u003c/h2\u003e \u003cp\u003eGas exchange was performed using a portable gas-exchange system (LI-6400, Li-CorInc, Lincoln, NE, USA) equipped with 2x3 cm light-source chamber. Prior to measurements, the branches were cut early in the morning, rehydrated by placing the cut ends in water, and kept in a shaded, cool environment to maintain their physiological integrity. Ambient conditions were recorded, the temperature was maintained at 25\u0026deg;C, the humidity of the incoming air was kept at 60% and radiation was fixed at 1500 \u0026micro;mol photons m⁻\u0026sup2; s⁻\u0026sup1;. The CO\u003csub\u003e2\u003c/sub\u003e are reserved at 400 \u0026micro;mol CO₂ mol⁻\u0026sup1; air. After reaching steady-state, measurements of net photosynthesis (An), stomatal conductance (gs) and transpiration (T), were calculated according to Von Caemmerer and Farquhar (1981). Instantaneous Water Use Efficiency (Wuei) was calculated as the ratio between (An) and (gs).\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e\u003cb\u003e2.5.3. Xylem specific conductivity and the percent loss of conductivity\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eSpecific hydraulic conductivity (Ks) was determined using the XYLEM (Embolism Meter, Bronkhorst, Montigny-les-Cormeilles, France). Branches were collected early in the morning, immediately recut under water to avoid xylem embolism, and transported to the laboratory in sealed plastic bags with moist paper towels to prevent desiccation. The samples were stored in a cool environment and processed within a few hours of collection. Before measuring the hydraulic conductivity (Kh), all branch segments were flushed with degassed, filtered water to remove any existing embolisms and ensure maximum conductivity. Kh was calculated as the ratio between the flow rate through each segment and the corresponding hydrostatic pressure gradient. The xylem cross-sectional area was then used to convert Kh into specific hydraulic conductivity (Ks, kg m⁻\u0026sup1; MPa⁻\u0026sup1; s⁻\u0026sup1;) following Tyree et al. (2005). The percent loss of conductivity (PLC), reflecting xylem cavitation, was calculated as:\u003c/p\u003e \u003cp\u003ePLC (%)\u0026thinsp;=\u0026thinsp;100*(K\u003csub\u003emax\u003c/sub\u003e-K\u003csub\u003ei\u003c/sub\u003e)/K\u003csub\u003emax\u003c/sub\u003e)\u003c/p\u003e \u003cp\u003eWhere: K\u003csub\u003emax\u003c/sub\u003e: maximal conductivity; K\u003csub\u003ei\u003c/sub\u003e: initial conductivity; PLC is the percent loss of conductivity due to cavitation.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Statistical analysis\u003c/h2\u003e \u003cp\u003eOne-way ANOVA was performed for all collected data. Means significant differences were performed using the Newman\u0026ndash;Keuls\u0026rsquo;s tests at \u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.05\u003c/em\u003e. Statistical analysis was realized using the SAS software. ACP was conducted using SPSS software. All values are presented as the mean of three replications\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Evapotranspiration, soil water content (SWC), and water balance deficit\u003c/h2\u003e \u003cp\u003eThe analysis of the water balance (P \u0026ndash; ETo) from 2014 to 2019 revealed distinct seasonal trends between the two studied bioclimates (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). At the sub-humid Rimel site, a water deficit persisted for most of the year, with the most severe deficits occurring from May to August. The maximum monthly deficit reached \u0026minus;\u0026thinsp;201 mm in July, indicating intense summer water stress. In contrast, the humid Sejnane site exhibited smaller deficits during the same period, with a maximum of \u0026minus;\u0026thinsp;182 mm in July. Overall, Sejnane experienced a shorter deficit period and a smaller total annual deficit (\u0026ndash;147 mm) compared to Rimel (\u0026ndash;580 mm), suggesting better water availability throughout the year. The soil water content (SWC) results also confirmed this pattern, showing that the soil at Sejnane was more humid (14.49%) than at Rimel (11.62%) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePrecipitation (P), Evapotranspiration (ETo) and the water balance deficit (P-ETo) of the two studied bioclimates (period 2014\u0026ndash;2019)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"15\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBioclimates\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"12\" nameend=\"c14\" namest=\"c3\"\u003e \u003cp\u003eMonths\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eJ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003eD\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cb\u003eSub-humid (Rimel site)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e627\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eETo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e107\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e141\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e201\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e173\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e112\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e1207\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP-ETo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-201\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-132\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e-580\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cb\u003eHumid (Sejnane site)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e135\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e129\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e182\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e931\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eETo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e177\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e1078\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP-ETo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e154\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-167\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-182\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-159\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e-147\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSoil Water Content measured in September 2019\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSWC (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRimel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e11.62\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSejnane\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e14.49\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.2. \u003cem\u003eEucalyptus\u003c/em\u003e production under two bioclimatic conditions\u003c/h2\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1. Fruit production\u003c/h2\u003e \u003cp\u003eAcross both bioclimates (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), \u003cem\u003eE. maculata\u003c/em\u003e and \u003cem\u003eE. paniculata\u003c/em\u003e consistently produced the highest fruit yields, with significantly greater production recorded at the humid Sejnane site (\u003cem\u003eE. maculata\u003c/em\u003e: 85\u0026thinsp;\u0026plusmn;\u0026thinsp;6 g; \u003cem\u003eE. paniculata\u003c/em\u003e: 10.46\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5 g) compared to the sub-humid Rimel site (\u003cem\u003eE. maculata\u003c/em\u003e: 31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46 g; \u003cem\u003eE. paniculata\u003c/em\u003e: 30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.73 g). In contrast, \u003cem\u003eE. camaldulensis\u003c/em\u003e showed the lowest fruit yield at both sites, with 9.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 g at Sejnane and 17.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.04 g at Rimel. Statistical analysis confirmed significant differences among species and sites (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2. Leaf production\u003c/h2\u003e \u003cp\u003eIn the sub-humid bioclimate (Rimel site, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), well-fruited \u003cem\u003eEucalyptus\u003c/em\u003e individuals exhibited greater leaf biomass compared to poorly fruited plants. Among the three species, \u003cem\u003eE. paniculata\u003c/em\u003e recorded the highest average leaf weight (0.0663\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0035 kg). Conversely, in the humid bioclimate (Sejnane site, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), \u003cem\u003eE. maculata\u003c/em\u003e showed the greatest leaf biomass, followed by \u003cem\u003eE. paniculata\u003c/em\u003e and \u003cem\u003eE. camaldulensis\u003c/em\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.2.3. Twig production\u003c/h2\u003e \u003cp\u003eTwig biomass followed a similar pattern to that of leaves across both bioclimates (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The highest twig weight was observed for \u003cem\u003eE. paniculata\u003c/em\u003e at the sub-humid site and for \u003cem\u003eE. maculata\u003c/em\u003e at the humid site. Statistical analysis indicated that both site and species significantly influenced twig and leaf production (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Physiological performance of \u003cem\u003eEucalyptus\u003c/em\u003e under two bioclimatic conditions\u003c/h2\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1. Leaf water potential\u003c/h2\u003e \u003cp\u003eStatistical analysis revealed that leaf water potential (Ψ) varied significantly with bioclimate, species, and fruit production (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). \u003cem\u003eEucalyptus\u003c/em\u003e species cultivated under sub-humid conditions exhibited higher Ψ values (\u0026ndash;0.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42 to \u0026minus;\u0026thinsp;0.39\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17 MPa) than those grown in humid conditions (\u0026ndash;0.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7 to \u0026minus;\u0026thinsp;0.96\u0026thinsp;\u0026plusmn;\u0026thinsp;6.3 MPa) (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Poorly fruited individuals generally displayed higher Ψ values than well-fruited ones. The highest Ψ values were recorded for poorly fruited \u003cem\u003eE. camaldulensis\u003c/em\u003e at the sub-humid site and well-fruited \u003cem\u003eE. maculata\u003c/em\u003e at the humid site.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLeaf water potential of poorly fruited and well fruited \u003cem\u003eEcucalyptus camaldulensis, E.maculata and E. paniculata\u003c/em\u003e plant species in sub humid (Rimel site) and humid (Sejnane site) bioclimates (September 2019).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePlant species\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eΨ (Mpa)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSub-humid bioclimate (Rimel)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHumid bioclimate (Sejnane)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camaldulensis\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5 bc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camalduensis\u003c/em\u003e well-fruting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.57 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.68\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9 b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.27\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.04 bc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.39\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.96\u0026thinsp;\u0026plusmn;\u0026thinsp;6.3 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.28\u0026thinsp;\u0026plusmn;\u0026thinsp;1.02 c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e well fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7 c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003eDifferent letters denote significant differences (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2. Gas exchange response patterns\u003c/h2\u003e \u003cp\u003eGas exchange parameters were significantly affected by bioclimatic conditions, species, and fruit production (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Net photosynthetic rate (Aₙ), stomatal conductance (gₛ), transpiration (Tr), and intrinsic water-use efficiency (WUEi) were significantly higher in all species grown under humid conditions and in well-fruited plants compared to poorly fruited ones (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). These parameters declined markedly under sub-humid conditions. Among species, \u003cem\u003eE. paniculata\u003c/em\u003e exhibited the highest physiological performance in both bioclimates, whereas \u003cem\u003eE. maculata\u003c/em\u003e showed the lowest.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNet photosynthesis (An), stomatal conductance(gs), transpiration (Tr) and Water Use Efficiency (Wuei) of poorly fruited and well fruited \u003cem\u003eEcucalyptus camaldulensis, E.maculata and E. paniculata\u003c/em\u003e plant species in sub humid (Rimel site) and humid (Sejnane site) bioclimates.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAn\u003c/p\u003e \u003cp\u003e(\u0026micro;mol m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003es\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGs\u003c/p\u003e \u003cp\u003e(mol.m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003es\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTr\u003c/p\u003e \u003cp\u003e(mol. m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. s\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWUEi\u003c/p\u003e \u003cp\u003e(\u0026micro;molCO2. mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e H2O)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eHumid bioclimate (Sejnane site)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.021\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.079\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.018\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.895\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e well-fruting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.427\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.092\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.020\u0026thinsp;\u0026plusmn;\u0026thinsp;0.036 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.313\u0026thinsp;\u0026plusmn;\u0026thinsp;0.58 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.142\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.070\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.044\u0026thinsp;\u0026plusmn;\u0026thinsp;0.160 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.009\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30 d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e well-fruting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.203\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.077\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.056\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.033\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51 d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camaldulensis\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.693\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 abc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.033\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.925\u0026thinsp;\u0026plusmn;\u0026thinsp;0.017 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.991\u0026thinsp;\u0026plusmn;\u0026thinsp;0.57 c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camaldulensis\u003c/em\u003e well-fruiting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.773\u0026thinsp;\u0026plusmn;\u0026thinsp;0,38 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.034\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.055\u0026thinsp;\u0026plusmn;\u0026thinsp;0.114 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.524\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eSub-humid bioclimate (Rimel site)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.045\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.812\u0026thinsp;\u0026plusmn;\u0026thinsp;0.044 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.048\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.927\u0026thinsp;\u0026plusmn;\u0026thinsp;0.164 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.73\u0026thinsp;\u0026plusmn;\u0026thinsp;0.55 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.032\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.017\u0026thinsp;\u0026plusmn;\u0026thinsp;0.017 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.182\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20 d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.039\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.019\u0026thinsp;\u0026plusmn;\u0026thinsp;0.026 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.826\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21 c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camaldulensis\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.020\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.739\u0026thinsp;\u0026plusmn;\u0026thinsp;0.295 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.978\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camaldulensis\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.025\u0026thinsp;\u0026plusmn;\u0026thinsp;0.015 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.800\u0026thinsp;\u0026plusmn;\u0026thinsp;0.208 cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.050\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eDifferent letters denote significant differences (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section3\"\u003e \u003ch2\u003e3.3.3. Variation in hydraulic traits\u003c/h2\u003e \u003cp\u003eXylem-specific conductivity (Kₛ) and percentage loss of conductivity (PLC) varied significantly among species, bioclimates, and fruiting levels (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e) (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Kₛ values were generally higher at the Rimel site (sub-humid) than at Sejnane (humid), whereas PLC values showed the opposite trend. Well-fruited plants displayed lower Kₛ and higher PLC values under both bioclimates. Notably, heavily fruiting \u003cem\u003eE. paniculata\u003c/em\u003e individuals exhibited the lowest Kₛ and PLC values across both sites, suggesting higher hydraulic regulation under reproductive stress.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eXylem specific conductivity (KS) and the percent loss of conductivity (PLC %) of poorly fruited and well fruited\u0026rsquo; \u003cem\u003eEucalyptus camaldulensis, E. maculata, E. paniculata\u003c/em\u003e plant species in sub humid (Rimel site) and humid (Sejnane site) bioclimates.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKS (Kg.m\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.MPa\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePLC (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eHumid (Sejnane site)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.7399\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0519 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.73 d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0654\u0026thinsp;\u0026plusmn;\u0026thinsp;0.084 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.86 c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.7509\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0877 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26 abc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0916\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0108 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e59.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camalendensis\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.682\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0906 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55.37\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19 abc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camalendensis\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0978\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0012 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e63.87\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eSub-Humid (Rimel site)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.043\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0056 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e66.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25 c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. paniculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0315\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0033 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e74.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0503\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0027 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72 ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. maculata\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0094\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0061 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e89.76\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18 b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camalendensis\u003c/em\u003e poorly fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0191\u0026thinsp;\u0026plusmn;\u0026thinsp;0.00245 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e96.174\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. camalendensis\u003c/em\u003e well-fruited\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.005919\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0008 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e97.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23 a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003eDifferent letters denote significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Correlations among analyzed variables\u003c/h2\u003e \u003cp\u003eCorrelation analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) revealed a positive and significant relationship between fruit production (FP), xylem conductivity (Kₛ), transpiration (Tr), and stomatal conductance (gₛ). Leaf production (LP) was positively correlated with net photosynthesis (Aₙ), relationships that characterized the humid bioclimate. In contrast, hydraulic parameters (Ψ, PLC, WUEi) showed strong positive intercorrelations under sub-humid conditions, distinguishing \u003cem\u003eEucalyptus\u003c/em\u003e responses in this bioclimate.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe growing frequency and intensity of droughts, resulting from altered precipitation regimes, represent a major threat to tropical and subtropical forest ecosystems (Zhou et al., 2011; Davidson et al., 2012). Prolonged drought periods can increase tree mortality, reduce forest biomass productivity, and diminish carbon sequestration capacity in natural forests (Chaves et al., 2002; Zhou et al., 2013). Furthermore, Bleby et al. (2012) reported that planted forests tend to be more vulnerable to extreme environmental stress than natural forests, mainly due to their lower ecological resilience.\u003c/p\u003e \u003cp\u003e \u003cem\u003eEucalyptus\u003c/em\u003e species play an important ecological and economic role in North Africa, particularly as introduced species used to prevent soil erosion and supply timber (Laclau, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In Tunisia, \u003cem\u003eEucalyptus\u003c/em\u003e represents the most widespread hardwood genus, covering approximately 5% of the total national forest area (DGF, 2010). As Tunisia is already below the water stress threshold (Oxford Analytica, 2023), understanding \u003cem\u003eEucalyptus\u003c/em\u003e water requirements and physiological responses to drought is increasingly critical. Water deficit remains the primary threat to \u003cem\u003eEucalyptus\u003c/em\u003e plantations, as this genus generally favors humid environments. Nevertheless, \u003cem\u003eEucalyptus\u003c/em\u003e is extensively used in reforestation programs worldwide (Zerga et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), especially across the southern Mediterranean region, which has experienced intensified drought conditions over recent decades (Lee et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). It is therefore essential to identify taxa that are less vulnerable to abiotic stress, in order to minimize potential impacts of climate change (Booth, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Da Silva et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo better characterize adaptive mechanisms in \u003cem\u003eEucalyptus\u003c/em\u003e, it is important to examine its physiological and morphological responses under contrasting environmental conditions. This macroecological study assessed three \u003cem\u003eEucalyptus\u003c/em\u003e species (\u003cem\u003eE. paniculata\u003c/em\u003e, \u003cem\u003eE. camaldulensis\u003c/em\u003e, and \u003cem\u003eE. maculata\u003c/em\u003e) cultivated under two distinct bioclimatic conditions in Tunisia. The results demonstrated that \u003cem\u003eEucalyptus\u003c/em\u003e species grown in the two arboreta\u0026mdash;Sejnane (humid) and Rimel (sub-humid)\u0026mdash;displayed considerable plasticity and an ability to acclimate and grow outside their native range. Under the humid conditions of Sejnane, all species showed improved growth performance compared to those cultivated at Rimel. Similar patterns have been reported by several authors, who observed increased biomass accumulation under wetter conditions (Ghannoum et al., 2010; Dieleman et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Pagotto et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Way, 2013).\u003c/p\u003e \u003cp\u003eAmong the studied taxa, \u003cem\u003eE. paniculata\u003c/em\u003e exhibited the highest productivity and physiological performance, outperforming \u003cem\u003eE. camaldulensis\u003c/em\u003e and \u003cem\u003eE. maculata\u003c/em\u003e under humid conditions. Nonetheless, all three species maintained satisfactory physiological performance under the more stressful sub-humid conditions of Rimel, demonstrating a certain degree of resilience. According to Argus et al. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), E. \u003cem\u003ecamaldulensis\u003c/em\u003e typically shows low stomatal conductance (gₛ) as an adaptive mechanism for water conservation. Other studies indicate that \u003cem\u003eEucalyptus\u003c/em\u003e species combine morphological and physiological adjustments to cope with drought stress (Garc\u0026iacute;a et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). For instance, \u003cem\u003eE. camaldulensis\u003c/em\u003e seedlings from semi-arid Australia develop extensive adventitious roots, increased stem porosity, and hypertrophy to improve water uptake and storage (Gibson, 1995; Zhang et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Leaf morphological adjustments and variations among \u003cem\u003eEucalyptus\u003c/em\u003e species have also been linked to bioclimatic conditions (Bustamante et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe physiological capacities observed in this study largely depended on environmental conditions, especially soil moisture and water balance, which regulate foliage activity and photosynthetic efficiency (Oren et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Shao et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Moreover, fruiting performance correlated positively with hydraulic traits such as stomatal conductance, transpiration, and xylem conductivity. These relationships support the approach proposed by Shani et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), which emphasizes the use of physiological parameters as reliable indicators for selecting drought-tolerant genotypes. Our results showed that plants grown under the sub-humid conditions of Rimel experienced reduced gas exchange, consistent with previous findings for \u003cem\u003eE. grandis\u003c/em\u003e, \u003cem\u003eE. urophylla\u003c/em\u003e, \u003cem\u003eE. camaldulensis\u003c/em\u003e, \u003cem\u003eE. torelliana\u003c/em\u003e, and \u003cem\u003eE. phaeotrica\u003c/em\u003e under water stress (Lima et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Shang et al., 2016).\u003c/p\u003e \u003cp\u003eAt Rimel, \u003cem\u003eEucalyptus\u003c/em\u003e species also exhibited high vulnerability to cavitation, as indicated by elevated PLC values and strongly negative water potentials. This vulnerability was accompanied by a simultaneous decline in xylem-specific conductivity, underscoring the close link between hydraulic function and soil water availability. Similar results were reported by Shang et al. (2016) and Liu et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) in \u003cem\u003eE. urophylla\u003c/em\u003e plantations under periodic drought. The observed decline in intrinsic water-use efficiency (WUEi) under high water stress conditions likely reflects increased physiological constraints on carbon assimilation. Butler et al. (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) emphasized the importance of water potential as a diagnostic measure of plant water status, noting that reduced soil water potential leads to lower leaf water potential, decreased stomatal conductance, and reduced photosynthetic rates. This cascade effect ultimately limits chlorophyll content and light absorption capacity (Bhusal et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBeyond the implications for \u003cem\u003eEucalyptus\u003c/em\u003e plantations, these findings contribute to the broader understanding of forest adaptation strategies in regions experiencing rising aridity (Dry, 2013). As drought events become more frequent and severe globally, developing a deeper understanding of species-specific physiological responses is essential for guiding reforestation programs, maintaining forest productivity, and enhancing ecosystem resilience in the face of climate change.\u003c/p\u003e"},{"header":"6. Conclusion","content":"\u003cp\u003eThis study highlights the importance of understanding species-specific responses of \u003cem\u003eEucalyptus\u003c/em\u003e to changing climatic conditions, particularly under increasing water scarcity. The results demonstrate significant variability in physiological performance among species and sites, underscoring the adaptive capacity and ecological plasticity of this genus. The Sejnane provenance, thriving under humid conditions, exhibited superior physiological tolerance to drought compared with the Rimel provenance, adapted to sub-humid environments. These differences emphasize the importance of selecting \u003cem\u003eEucalyptus\u003c/em\u003e species and provenances based on their climatic adaptability to optimize reforestation success in water-limited regions.\u003c/p\u003e \u003cp\u003eAmong the species examined, \u003cem\u003eE. paniculata\u003c/em\u003e showed a strong ability to acclimate across contrasting edaphoclimatic conditions, maintaining efficient water use and physiological performance under stress. This adaptability positions \u003cem\u003eE. paniculata\u003c/em\u003e as a promising candidate for future reforestation and afforestation programs in areas facing recurrent drought.\u003c/p\u003e \u003cp\u003eOverall, the study provides valuable insights into the morpho-physiological mechanisms underlying drought tolerance in \u003cem\u003eEucalyptus\u003c/em\u003e, offering practical guidance for species selection and forest management under current and future climate change scenarios. By integrating such adaptive traits into reforestation planning, it is possible to enhance forest resilience, ensure sustainable productivity, and support ecosystem restoration efforts in arid and semi-arid regions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eS.F. conceptualized the study and prepared the initial draft of the manuscript. A.S. supervised the overall work, contributed to the critical review, and provided major revisions to improve the scientific quality. Y.Y. contributed to the literature collection, data organization, and figure preparation. FY participated in data curation, formatting, and manuscript editing. W. E. and H.B. assisted in conceptualization and validation of scientific content and contributed to the final proofreading and formatting of references. All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data supporting the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing financial interests or personal relationships that could have influenced the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University (IMSIU) (grant number IMSIU-DDRSP2601).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eArgus RE, Colmer TD, Grierson PF (2015) Physiological flood tolerance and recovery. Plant Cell Environ 38:1189\u0026ndash;1199. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/pce.12473\u003c/span\u003e\u003cspan address=\"10.1111/pce.12473\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhusal N, Han SG, Yoon TM (2019) Impact of drought stress on photosynthetic response, leaf water potential, and stem sap flow in two cultivars of bi-leader apple trees (Malus\u0026times; domestica Borkh). Sci Hort 246:535\u0026ndash;543. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.scienta.2018.11.021\u003c/span\u003e\u003cspan address=\"10.1016/j.scienta.2018.11.021\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhusal N, Park I, Jeong H, Choi S, Han BH, Yoon SG TM (2023) Photosynthetic traits and plant hydraulic dynamics in Gamhong apple cultivar under drought, waterlogging, and stress recovery periods. Sci Hort 321:112276\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoland DJ, Brooker MIH, Chippendale GM, Hall N, Hyland BP, Johnston RD, Turner JD (eds) (2006) For trees Aust. CSIRO publishing\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBooth TH (2013) \u003cem\u003eEucalypt\u003c/em\u003e plantations and climate change. Ecol Manag 301:28\u0026ndash;34\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBosi C, Pezzopane JRM, Sentelhas PC (2020) Silvopastoral system with Eucalyptus as a strategy for mitigating the effects of climate change on Brazilian pasturelands. Acad Bras Cienc 92. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1590/0001-3765202020180425\u003c/span\u003e\u003cspan address=\"10.1590/0001-3765202020180425\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBullock SH (1986) Climate of Chamela, Jalisco, and trends in the south coastal region of Mexico. Arch Met Geophys Bioclimatol B 36:297\u0026ndash;316. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/BF02263135\u003c/span\u003e\u003cspan address=\"10.1007/BF02263135\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBustamante M, Santos GM, Lemos-Filho JP, Almeida JPN (2021) Adaptive plasticity in leaf traits of Eucalyptus grandis along a climate gradient. Ecol Manag 479:118611. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foreco.2020.118611\u003c/span\u003e\u003cspan address=\"10.1016/j.foreco.2020.118611\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eButler JB, Harrison PA, Vaillancourt RE, Steane DA, Tibbits JFG, Potts BM (2022) Climate Adaptation, Drought Susceptibility, and Genomic-Informed Predictions of Future Climate Refugia for the Australian Forest Tree \u003cem\u003eEucalyptus globulus\u003c/em\u003e. Forests 13:575. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/f13040575\u003c/span\u003e\u003cspan address=\"10.3390/f13040575\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCorreia B, Pint\u0026oacute;-Marijuan M, Neves L, Brossa R, Dias MC, Costa A, Pinto G (2014) Water stress and recovery in the performance of two \u003cem\u003eEucalyptus globulus\u003c/em\u003e clones: physiological and biochemical profiles. Physiol Plant 150(4):580\u0026ndash;592. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/ppl.12110\u003c/span\u003e\u003cspan address=\"10.1111/ppl.12110\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCosta DD, da Silva Pereira TA, Fragoso CR Jr, Madani K, Uvo CB (2016) Understanding drought dynamics during dry season in Eastern Northeast Brazil. Front Earth Sci 4:69. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/feart.2016.00069\u003c/span\u003e\u003cspan address=\"10.3389/feart.2016.00069\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDa Silva PHM, Araujo MJ, Lee DJ et al (2022) Adaptability and stability of novel eucalypt species and provenances across environments in Brazil at two assessment. New Forest 53:779\u0026ndash;796. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11056-021-09886-7\u003c/span\u003e\u003cspan address=\"10.1007/s11056-021-09886-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Moraes DHM, Mesquita M, Graciano-Ribeiro D, de Ara\u0026uacute;jo DS, Battisti R, Flores RA, Casaroli D (2022) The effect of xylem vessel diameter on potential hydraulic conductivity in different rice stem longitudinal positions. Flora 295:152147. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.flora.2022.152147\u003c/span\u003e\u003cspan address=\"10.1016/j.flora.2022.152147\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDieleman WI, Vicca S, Dijkstra FA, Hagedorn F, Hovenden MJ, Larsen KS, \u0026hellip; and, Janssens IA (2012) Simple additive effects are rare: a quantitative review of plant biomass and soil process responses to combined manipulations of CO2 and temperature. Glob chang biol 18(9):2681\u0026ndash;2693. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5902/198050981829\u003c/span\u003e\u003cspan address=\"10.5902/198050981829\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDye P (2013) A review of changing perspectives on Eucalyptus water-use in South Africa. Ecol Manag 301:51\u0026ndash;57. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foreco.2012.08.027\u003c/span\u003e\u003cspan address=\"10.1016/j.foreco.2012.08.027\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGarc\u0026iacute;a LY, Rubilar R, Valverde JC, Emhart V, Bascu\u0026ntilde;\u0026aacute;n L, Medina A, Bozo D (2023) Morphological, physiological and carbon balance response of Eucalyptus genotypes under water stress. New Forest 1\u0026ndash;17. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11056-023-09985-7\u003c/span\u003e\u003cspan address=\"10.1007/s11056-023-09985-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhannoum O, Way DA (2011) On the role of ecological adaptation and geographic distribution in the response of trees to climate change. Tree Physiol 31(12):1273\u0026ndash;1276. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/treephys/tpr115\u003c/span\u003e\u003cspan address=\"10.1093/treephys/tpr115\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGibson A, Bachelard EP, Hubick KT (1995) Relationship between climate and provenance variation in \u003cem\u003eEucalyptus camaldulensis\u003c/em\u003e Dehnh. Funct Plant Biol 22(3):453\u0026ndash;460. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1071/PP9950453\u003c/span\u003e\u003cspan address=\"10.1071/PP9950453\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGon\u0026ccedil;alves JL, Alvares C, Rocha JH, Brandani CB, Hakamada R (2017) Eucalypt plantation management in regions with water stress. South For: J Sci 79(3):169\u0026ndash;183. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2989/20702620.2016.1255415\u003c/span\u003e\u003cspan address=\"10.2989/20702620.2016.1255415\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuarnaschelli AB, Garau AM, Lemcoff JH (2012) Water stress and afforestation: a contribution to ameliorate forest seedling performance during the establishment. Water stress 2:74\u0026ndash;110\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eH\u0026eacute;roult A, LIN YS, Bourne A, Medlyn BE, Ellsworth DS (2013) Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought. Plant Cell Env 36(2):262\u0026ndash;274. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1365-3040.2012.02570.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1365-3040.2012.02570.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHolbrook NM, Burns MJ, Field CB (1995) Negative xylem pressures in plants: a test of the balancing pressure technique. Science 270(5239):1193\u0026ndash;1194. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.1126/science.270.5239.11\u003c/span\u003e\u003cspan address=\"https://10.1126/science.270.5239.11\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHolbrook NM, Burns MJ, Field CB (1995) Negative xylem pressures in plants: a test of the balancing pressure technique. Science 270(5239):1193\u0026ndash;1194. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://10.1126/science.270.5239.11\u003c/span\u003e\u003cspan address=\"https://10.1126/science.270.5239.11\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuante P, Rinc\u0026oacute;n E (1997) Responses to light changes in tropical deciduous woody seedlings with contrasting growth rates. Oecologia 113:53\u0026ndash;66. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s004420050353\u003c/span\u003e\u003cspan address=\"10.1007/s004420050353\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJames C, Reid M, Capon S (2016) Climate change and the future of Australian riverine vegetation. Vegetation of Australian Riverine landscapes. Biol Ecol manag. 387\u0026ndash;405\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLaclau JP (2018) Managing \u003cem\u003eEucalyptus\u003c/em\u003e Plantations under Global Changes, IUFRO, Ed. Montpellier: Le Corum, France, 2018\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee H, Calvin K, Dasgupta D, Krinmer G, Mukherji A, Thorne P, Zommers Z (2023) Synthesis report of the IPCC Sixth Assessment Report (AR6), Longer report. IPCC\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLewis JD, Phillips NG, Logan BA, Hricko CR, Tissue DT (2011) Leaf photosynthesis, respiration and stomatal conductance in six \u003cem\u003eEucalyptus\u003c/em\u003e species native to mesic and xeric environments growing in a common garden. Tree Physiol 31(9):997\u0026ndash;1006. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/treephys/tpr087\u003c/span\u003e\u003cspan address=\"10.1093/treephys/tpr087\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLima WDP, Jarvis P, Rhizopoulou S (2003) Stomatal responses of \u003cem\u003eEucalyptus\u003c/em\u003e species to elevated CO2 concentration and drought stress. Sci Agricol 60:231\u0026ndash;238. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1590/S0103-90162003000200005\u003c/span\u003e\u003cspan address=\"10.1590/S0103-90162003000200005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu X, Wang N, Cui R, Song H, Wang F, Sun X, Du N, Wang H, Wang R (2021) Quantifying key points of hydraulic vulnerability curves from drought-rewatering experiment using differential method. Front Plant Sci 12:627403. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/fpls.2021.627403\u003c/span\u003e\u003cspan address=\"10.3389/fpls.2021.627403\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL\u0026oacute;pez R, Cano FJ, Choat B, Cochard H, Gil L (2020) Coordination of stem and leaf traits define different strategies to face drought in European beech, Scots pine and wild service tree. Tree Physiol 40(2):164\u0026ndash;175. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/treephys/tpz114\u003c/span\u003e\u003cspan address=\"10.1093/treephys/tpz114\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL\u0026oacute;pez R, Rodr\u0026iacute;guez-Calcerrada J, Gil L (2009) Physiological and morphological response to water deficit in seedlings of five provenances of \u003cem\u003ePinus canariensis\u003c/em\u003e: potential to detect variation in drought-tolerance. Trees 23:509\u0026ndash;519. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00468-008-0297-5\u003c/span\u003e\u003cspan address=\"10.1007/s00468-008-0297-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOren R et al (1999) Survey and synthesis of intra and interspecific variation in stomatal sensitivity to vapour pressure deficit. Plant Cell Env 22:1515\u0026ndash;1526. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1046/j.1365-3040.1999.00513.x\u003c/span\u003e\u003cspan address=\"10.1046/j.1365-3040.1999.00513.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePagotto MA, Arag\u0026atilde;o JRV, Hornink B, Menezes IRN, Tomazello-Filho M, Lisi CS, Leal IR, Tabarelli M (2025) Biomass production by tree species is negatively affected by decreased precipitation and chronic anthropogenic disturbance in a Caatinga dry forest. J Arid Environ 228 Article 105340. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jaridenv.2025.105340\u003c/span\u003e\u003cspan address=\"10.1016/j.jaridenv.2025.105340\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePita-Barbosa A, Oliveira LA, De Barros NF, Hodecker BER, Oliveira FS, Ara\u0026uacute;jo WL, Martins SC (2023) Developing a Roadmap to Define a Potential Ideotype for Drought Tolerance in \u003cem\u003eEucalyptus\u003c/em\u003e. Sci 69(1):101\u0026ndash;114. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/forsci/fxac044\u003c/span\u003e\u003cspan address=\"10.1093/forsci/fxac044\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRodr\u0026iacute;guez-Gamir J, Sancho-Knapik D, Peguero-Pina JJ, Gil-Pelegr\u0026iacute;n E (2021) Hydraulic traits and leaf responses in \u003cem\u003ePinus halepensis\u003c/em\u003e seedlings under severe drought conditions and recovery. Ecol Manag 492:119191\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eScholander PF, Bradstreet ED, Hemmingsen EA, Hammel HT (1965) Sap Pressure in Vascular Plants: Negative hydrostatic pressure can be measured in plants. Science 148(3668):339\u0026ndash;346. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1126/science.148.3668.3\u003c/span\u003e\u003cspan address=\"10.1126/science.148.3668.3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSerrano L, Penuelas J (2005) Contribution of physiological and morphological adjustments to drought resistance in two Mediterranean tree species. Biol Plant 49:551\u0026ndash;559. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10535-005-0049-y\u003c/span\u003e\u003cspan address=\"10.1007/s10535-005-0049-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShahzad MA et al (2016) Drought stress and morphophysiological responses in plants. Water stress and crop plants: A sustainable approach. 2: 452\u0026ndash;467. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/9781119054450.ch27\u003c/span\u003e\u003cspan address=\"10.1002/9781119054450.ch27\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShani MY, Ditta A, Khan MKR, Rasheed A, Azhar MT, Khan AS (2025) Deciphering drought tolerance in cotton genotypes through integrated morpho-physiological and biochemical markers at flowering stage. Sci Rep 15:44123. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41598-025-28237-6\u003c/span\u003e\u003cspan address=\"10.1038/s41598-025-28237-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShao S, Li G, Wang J, Wang Y, Qu M, Zhao H, Zhu W, Li J (2024) Temperature and soil attributes drive the regional variation in leaf anatomical traits of Populus euphratica. Global Ecol Conserv 54:e03107. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.gecco.2024.e03107\u003c/span\u003e\u003cspan address=\"10.1016/j.gecco.2024.e03107\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThomsen A, Schelde K, Dr\u0026oslash;scher P (2007) Mobile TDR for geo-referenced measurement of soil water content and electrical conductivity. Prec Agricul 8:213\u0026ndash;223. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11119-007-9041-1\u003c/span\u003e\u003cspan address=\"10.1007/s11119-007-9041-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhite DA, Beadle CL, Sands PJ, Worledge D, Honeysett JL (1999) Quantifying the effect of cumulative water stress on stomatal conductance of \u003cem\u003eEucalyptus\u003c/em\u003e globulus and \u003cem\u003eEucalyptus\u003c/em\u003e nitens: a phenomenological approach. Funct Plant Biol 26:17\u0026ndash;27. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1071/PP98023\u003c/span\u003e\u003cspan address=\"10.1071/PP98023\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZerga B, Warkineh B, Teketay D, Egner B (2021) The sustainability of reforesting landscapes with exotic species: A case study of eucalypts in Ethiopia. Sustainability: Sci Pract Policy 4., Article 5. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/s42055-021-00044-7\u003c/span\u003e\u003cspan address=\"10.1186/s42055-021-00044-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang J, Li X, Cui Y, Zhang C (2021) Plant physiological responses to drought stress and their management strategies in agriculture. Plants 10(4):687. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/plants10040687\u003c/span\u003e\u003cspan address=\"10.3390/plants10040687\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Z, Zhao P, McCarthy HR, Ouyang L, Niu J, Zhu L et al (2016) Hydraulic balance of a \u003cem\u003eEucalyptus\u003c/em\u003e urophylla plantation in response to periodic drought in low subtropical China. Front Plant Sci 7:1346. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/fpls.2016.01346\u003c/span\u003e\u003cspan address=\"10.3389/fpls.2016.01346\" 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":false,"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":"journal-of-plant-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpre","sideBox":"Learn more about [Journal of Plant Research](http://link.springer.com/journal/10265)","snPcode":"10265","submissionUrl":"https://www.editorialmanager.com/jpre/default2.aspx","title":"Journal of Plant Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Eucalyptus spp., drought tolerance, morpho-physiological adaptation, hydraulic traits, gas exchange, water-use efficiency, climatic variability","lastPublishedDoi":"10.21203/rs.3.rs-8554718/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8554718/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRegenerating forests must adapt to prevailing climatic conditions for several decades, and possibly over a century. Climate change is profoundly altering tree productivity and ecophysiological responses, with major impacts on forest ecosystems. Understanding the capacity of forest tree species to adapt to climate change, particularly drought, is therefore crucial for sustainable forest management. This study investigates variability in the physiological behavior of three \u003cem\u003eEucalyptus\u003c/em\u003e species (\u003cem\u003eE. camaldulensis\u003c/em\u003e, \u003cem\u003eE. maculata\u003c/em\u003e, \u003cem\u003eE. paniculata\u003c/em\u003e) growing under two bioclimates (humid and sub-humid). Gas exchange, hydraulic traits, morphological characteristics, and water availability were monitored to evaluate species performance. Significant differences in adaptive behavior were observed across species and sites (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e). The Sejnane provenance (humid) showed superior water status and physiological tolerance to drought compared with Rimel (sub-humid), reflecting better adaptation with lower evapotranspiration and water deficit. Morphological adjustments contributed to improved physiological performance under limited water. \u003cem\u003eE. paniculata\u003c/em\u003e displayed strong acclimation to both sites, maintaining efficient water control under stress, while \u003cem\u003eE. camaldulensis\u003c/em\u003e showed limited adaptive capacity. These findings are essential for identifying drought-resilient tree species suited for reforestation, supporting sustainable forest management and ecosystem restoration under changing climatic conditions.\u003c/p\u003e","manuscriptTitle":"Differential Adaptation of Eucalyptus Species through Morpho-physiological and Hydraulic Adjustments to Climate Variability","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-04 10:09:27","doi":"10.21203/rs.3.rs-8554718/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-02-02T09:35:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-09T11:27:43+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Plant Research","date":"2026-01-08T14:39:34+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-plant-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpre","sideBox":"Learn more about [Journal of Plant Research](http://link.springer.com/journal/10265)","snPcode":"10265","submissionUrl":"https://www.editorialmanager.com/jpre/default2.aspx","title":"Journal of Plant Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"94791431-221a-48b3-af7b-cc3eaaa91ffa","owner":[],"postedDate":"February 4th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-04T10:09:27+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-04 10:09:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8554718","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8554718","identity":"rs-8554718","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}