Grazing and Plateau Zokor Disturbance Exert Non-additive Effects on Soil Carbon Pools in Alpine Meadows of the Qinghai-Tibet Plateau

Grazing and Plateau Zokor Disturbance Exert Non-additive Effects on Soil Carbon Pools in Alpine Meadows of the Qinghai-Tibet Plateau | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 4 August 2025 V1 Latest version Share on Grazing and Plateau Zokor Disturbance Exert Non-additive Effects on Soil Carbon Pools in Alpine Meadows of the Qinghai-Tibet Plateau Authors : Yang Yang , Rui Mao , Huankun Leng , Yi Huang , Jianmin Yao , Tingyong Yang , Hong Jin , and Jian Yang [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.175431802.26306317/v1 230 views 134 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Grazing and plateau zokor ( Eospalax baileyi ) activities constitute critical biotic disturbances influencing soil carbon pool dynamics in the alpine meadows of the Qinghai-Tibet Plateau. However, their synergistic mechanisms remain poorly understood. Through dual-season sampling (July and October), this study utilized linear mixed models (LMM) and structural equation modeling (SEM) to evaluate soil carbon-nitrogen metrics (SOC, TIC, TC, TN) and physicochemical parameters (SBD, pH) across four treatments: undisturbed control (CK), grazing-only (G), zokor-only (Z), and combined disturbances (G×Z). The results revealed that: (1) Grazing effects elevated SOC, TN, and SBD (+15-30%) throughout the soil profile ( p <0.05), while concurrently suppressing TIC concentrations; (2) Zokor dynamics demonstrated seasonal stratification, with rainy-season SOC enrichment in surface soils (0-10 cm) contrasting with dry-season carbon-nitrogen retention in subsurface layers (20-30 cm); (3) Interaction mechanisms exhibited antagonistic suppression of TIC and non-additive responses of SOC and TN, which were potentially mediated by microbial mineralization thresholds. These results delineate the hierarchical regulation of biotic disturbances on soil carbon sequestration and offer mechanistic insights for alpine meadow carbon management under global change scenarios. Grazing and Plateau Zokor Disturbance Exert Non-additive Effects on Soil Carbon Pools in Alpine Meadows of the Qinghai-Tibet Plateau Yang Yang a,b , Rui Mao d , Huankun Leng a , Yi Huang b , Jianmin Yao e , Tingyong Yang e , Hong Jin c,* , and Jian Yang a,* a Sichuan Provincial Forest and Grassland Key Laboratory of Alpine Grassland Conservation and Utilization of Qinghai-Tibetan Plateau, College of Grassland Resources, Southwest Minzu University, Chengdu, China b Key Laboratory of Biodiversity and Environment on the Qinghai-Tibetan Plateau, Ministry of Education, School of Ecology and Environment, XiZang University, Lhasa, China c College of Life Sciences, Sichuan University, Chengdu, China d Xiaojin County Forestry and Grassland Bureau, Aba, China e Ganzi Tibetan Autonomous Prefecture Grassland Work Station, Ganzi, China E-mail address of the corresponding author: Hong Jin, [email protected] ; Jian Yang, [email protected] . Abstract: Grazing and plateau zokor ( Eospalax baileyi ) activities constitute critical biotic disturbances influencing soil carbon pool dynamics in the alpine meadows of the Qinghai-Tibet Plateau. However, their synergistic mechanisms remain poorly understood. Through dual-season sampling (July and October), this study utilized linear mixed models (LMM) and structural equation modeling (SEM) to evaluate soil carbon-nitrogen metrics (SOC, TIC, TC, TN) and physicochemical parameters (SBD, pH) across four treatments: undisturbed control (CK), grazing-only (G), zokor-only (Z), and combined disturbances (G×Z). The results revealed that: (1) Grazing effects elevated SOC, TN, and SBD (+15-30%) throughout the soil profile ( p <0.05), while concurrently suppressing TIC concentrations; (2) Zokor dynamics demonstrated seasonal stratification, with rainy-season SOC enrichment in surface soils (0-10 cm) contrasting with dry-season carbon-nitrogen retention in subsurface layers (20-30 cm); (3) Interaction mechanisms exhibited antagonistic suppression of TIC and non-additive responses of SOC and TN, which were potentially mediated by microbial mineralization thresholds. These results delineate the hierarchical regulation of biotic disturbances on soil carbon sequestration and offer mechanistic insights for alpine meadow carbon management under global change scenarios. Keywords : Alpine meadow; Soil organic carbon; Biotic disturbance; Non-additive effect; Structural equation modeling Introduction Alpine meadows, spanning approximately 58.83×10 6 h a-1 across the Qinghai-Tibetan Plateau (QTP), constitute the dominant vegetation type in this region (Gao et al., 2012). As the largest carbon reservoir within these ecosystems, the soil carbon pool stores 92- 95% of the total ecosystem carbon (≈277 Tg C) (Wang et al., 2021). The unique high-altitude, low-temperature conditions of the QTP result in slow soil carbon turnover rates, rendering this equilibrium highly vulnerable to external perturbations (Fan et al., 2008). Among these, biotic disturbances—particularly grazing and small fossorial mammals—play a pivotal role in modulating soil carbon dynamics and storage (James et al., 2009). The alpine meadow soil carbon pool is subject to multiple biotic disturbances, including those mediated by plant communities (Yan et al., 2019; Wei et al., 2019), livestock grazing (Rui et al., 2011; Zhang et al., 2018), and small burrowing mammals (Yurkewycz et al., 2014; Clark et al., 2016; Yu et al., 2017). Unlike plant-mediated effects, grazing and fossorial mammal activities induce more rapid and pronounced shifts in soil carbon pools (Fleming et al., 2014). These disturbances also indirectly reshape plant community structure, generating complex, system-wide repercussions for carbon cycling. As the most prevalent land-use practice on the QTP, grazing influences alpine meadows through three primary mechanisms: selective herbivory, trampling, and nutrient deposition via livestock excreta. By reducing aboveground biomass and litter production, grazing restricts carbon inputs to soils (Eldridge & Delgado- Baquerizo, 2017; Zhou et al., 2019; Jiang et al., 2020), while simultaneously altering root dynamics and soil nutrient cycling rates (Chuan et al., 2020). Trampling and excreta further modify key soil physicochemical properties (e.g., bulk density, pH) and nutrient fluxes, collectively impacting carbon storage at ecosystem scales (Shang et al., 2017; Ganjurjav et al., 2019). Intensive grazing has precipitated grassland degradation in some areas (Deng et al., 2017; Wang et al., 2019), with degraded or degradation-prone meadows frequently overlapping with habitats of the plateau zokor ( Eospalax baileyi )—a spatial correlation suggesting potential disturbance synergies. Figure 1 Study Area and Plateau Zokors ( Eospalax baileyi ) in the Area. The plateau zokor, a subterranean rodent endemic to the QTP, currently occupies a distribution range of 2.7×10 6 km 2 (Su et al., 2015). As a keystone ecosystem engineer, this species constructs extensive subterranean tunnel networks, creating void structures that physically reorganize the soil matrix. Their burrowing and nesting activities drive vertical nutrient redistribution and accelerate biogeochemical cycling, exerting profound impacts on alpine meadow carbon pools (James et al., 2009; Wilkinson et al., 2009). Despite considerable research on individual disturbances, the nature of interactions—whether synergistic or antagonistic—between grazing and zokor activity remains poorly resolved. Existing studies predominantly examine single-factor effects, neglecting potential non-additive interactions that may govern nonlinear responses in soil carbon dynamics. Based on current evidence, we hypothesize that grazing and zokor disturbances exert antagonistic effects on alpine meadow soil carbon pools. 2.Materials and methods 2.1. Study Sites The study was conducted in Ruoergai National Park (33°55′- 34°19′N, 102°08′-102°52′E), located on the southeastern QTP at elevations of 3,500- 3,600 m. The region exhibits a continental plateau cold-temperate monsoon climate with pronounced wet (June-September) and dry seasons. The vegetation is dominated by alpine Kobresia meadows, with the following floristic composition (mean relative abundance): Poaceae (35.2%), Cyperaceae (28.6%), Ranunculaceae (9.8%), Leguminosae (7.4%), Asteraceae (6.9%), Rosaceae (5.3%), and Polygonaceae (4.8%). Dominant species included Kobresia pygmaea (C.B. Clarke) C.B. Clarke, Carex alatauensis S.R. Zhang, Elymus nutans Griseb., Potentilla anserina L. (syn. Argentina anserina ), Artemisia mongolica (Fisch. ex Bess.), and Bistorta vivipara (L.) Delarbre. Soils were classified as Alpine Meadow Soil under the Chinese GB/T 17296-2009 standard and as Haplic Cambisols (WRB classification). The area serves as warm-season pasture for yaks ( Bos grunniens ) from late July to late October, with a grazing intensity of 2.3-2.5 livestock units/ha—consistent with moderate grazing pressure according to NY/T 635-2002 grassland carrying capacity standards. Plateau zokors exhibited bimodal activity: peak burrowing during March-May (plant green-up phase) and September-October (food caching period), with reduced activity in June-September (monsoon rains) and November-March (soil freezing period) (Ji et al., 2018). 2.2. Experimental Design and Sampling A preliminary field survey in May 2023 confirmed plateau zokors as the dominant fossorial herbivores in the study region (Table 1). Zokor mound density in disturbed areas was quantified using the standardized ’fresh mound’ census method. To capture seasonal dynamics, soil sampling was conducted in July (early warm-season grazing period, low zokor activity during rains) and October 2023 (post-grazing season, peak zokor activity post-rains). Sampling points spanned four bioturbation treatments: undisturbed control (CK), grazing-only (G), zokor-only (Z), and combined grazing+zokor (G&Z). Five spatially independent sampling points were established for each treatment type, totaling 20 points. Points within the same treatment type were separated by≥20 km straight-line distance. All sites were established in topographically uniform alpine meadows to isolate bioturbation and grazing effects from other environmental variables. At each sampling point, three randomly positioned 1-m²vegetation quadrats were established for community composition assessment and homogeneity verification. Five additional 1-m² soil sampling quadrats were randomly deployed per point. Based on zokor foraging ecology—primarily disturbing the 0-30 cm soil layer for respiratory adaptation during rains—soil cores were collected at 0-10 cm, 10-20 cm, and 20-30 cm depths via a five-point sampling scheme. Per depth interval, three composite soil nutrient samples (sieved to 2 mm, roots/gravel removed) and three intact SBD cores (61.8 mm diameter × 20 mm height stainless steel rings, 100 cm³ volume) were obtained. Nutrient samples were air-dried; SBD samples were oven-dried (105°C) to constant mass. This design yielded 60 nutrient and 60 SBD samples per season (July/October), totaling 240 samples. Table 1 Characteristics of Sampling Plots in the Study Area. Figure 2 Spatial distribution of sampling points across treatment types. 2.3. Soil analysis The soil nutrient samples were homogenized and sieved (2 mm) to remove debris. Soil organic carbon (SOC) was quantified using the potassium dichromate oxidation-external heating method. Total carbon (TC) and total nitrogen (TN) concentrations were determined via high-temperature combustion (900°C) and non-dispersive infrared absorption (NDIR) using an elemental analyzer (Elementar vario MAX cube, Germany). Soil pH was measured in a 1:2.5 (w/v) soil-water suspension with a calibrated pH meter (Leici PHS-3C, Shanghai, China). Soil bulk density (SBD) was calculated from the oven-dry mass (105°C, 48 h) of intact soil cores. All measurements were performed in triplicate, with mean values used for subsequent analyses. 2.4. Statistical analysis All statistical analyses were conducted in R 4.0.2. Data normality and homogeneity of variance were verified using Shapiro-Wilk and Levene’s tests, respectively; non-normal datasets were log-transformed to meet parametric assumptions. Linear mixed-effects models (LMMs) were implemented to evaluate the fixed effects of biotic disturbances (grazing, plateau zokor activity, and their interaction), soil depth (0-10, 10-20, and 20-30 cm), and sampling season (July vs. October) on soil carbon-nitrogen metrics (SOC, TC, TN) and physicochemical properties (SBD, pH), with plot-level spatial heterogeneity incorporated as a random effect. Post hoc comparisons were performed using Tukey’s HSD tests. To disentangle the mechanistic drivers of biotic disturbances on soil carbon dynamics, we employed structural equation modeling (SEM) to partition direct effects of grazing and zokor activity from indirect pathways mediated by TN and SBD. Spatiotemporal heterogeneity in carbon pool variability was assessed via two-way ANOVA and Mantel tests, with interaction plots visualizing depth-dependent disturbance effects. 3.1.Vertical distribution patterns of soil properties and their seasonal dynamics under bioturbation Analysis of the four experimental plots revealed significant bioturbation-induced modifications in the vertical stratification and seasonal variation of soil carbon and nitrogen pools (Table 2, Figure 3). Table 2 Concentrations of soil organic carbon (SOC), total carbon (TC), total nitrogen (TN), as well as soil bulk density (SBD) and pH at different depths in July and October in plots of four biological disturbance types. This table indicates that the concentrations of soil organic carbon (SOC), total carbon (TC), and total nitrogen (TN), as well as soil bulk density (SBD) and pH in the soils sampled in July and October, are significantly affected by biological disturbances and changes in soil depth. The values in the table are expressed as ”mean ± standard deviation”. Within each soil depth, different lowercase letter superscripts denote significant differences among different types of biological disturbances. Figure 3 Concentrations of soil organic carbon (SOC), total carbon (TC), and total nitrogen (TN), as well as soil bulk density (SBD) and pH in soils of different biological disturbance types in July and October. In control (CK) plots, SOC, TN, and SBD exhibited characteristic decreases with depth, while TIC showed an opposing trend. Although grazing elevated overall soil pH, no significant treatment × depth interactions were detected ( p > 0.05), suggesting bioturbation had minimal impact on pH dynamics. Grazing (G) plots demonstrated consistent seasonal patterns, with SOC, TN, and SBD increasing by 17-23%, 14-19%, and 8-12%, respectively, across all soil layers compared to CK. These effects were most pronounced at 20-30 cm depth, where TIC was simultaneously reduced by 9-15%. Despite SOC accumulation, TC remained statistically unchanged due to offsetting TIC losses. Zokor (Z) disturbance produced distinct seasonal stratification patterns. July sampling revealed enhanced SOC (22%), TC (18%), and TN (15%) accumulation in surface soils (0-10 cm) accompanied by 11% TIC suppression. By October, these effects had shifted downward, with 20-30 cm layers showing 19-24% increases in SOC/TC/TN and 13% lower TIC, while SBD decreased by 7-9% throughout the soil profile. The combined Grazing+Zokor (G&Z) treatment generated complex spatiotemporal responses. TN consistently increased (12-16% across depths) while TIC showed stronger suppression (18-22%) than in single-disturbance plots. SOC and TC responses exhibited seasonal depth-dependence: surface layers (0-10 cm) showed 8-11% SOC/TC reduction in July but 14% SOC accumulation in October, while deeper soils (20-30 cm) displayed 19-21% increases in July but neutral responses in October. SBD increases were attenuated (4-6% vs. G plots) due to antagonistic grazing-zokor interactions. The integrated results demonstrate that grazing uniformly enhanced C/N pools and SBD throughout the profile, while zokor activity drove seasonal vertical redistribution of C/N accompanied by SBD reduction. Combined disturbances amplified TN accumulation and TIC suppression while creating divergent SOC/TC patterns by season and depth. All treatments maintained stable pH (7.2-7.6), with only grazing producing marginal increases. Surface (0-10 cm) and deep (20-30 cm) soils showed coherent responses across treatments, whereas intermediate layers (10-20 cm) exhibited transitional, non-directional behavior, suggesting depth-specific sensitivity to bioturbation effects. Note: Percentage changes are reported relative to CK; statistical significance was assessed at α = 0.05 using mixed-effects models. 3.2. Correlations among bioturbation, soil properties, and spatiotemporal heterogeneity factors To elucidate the mechanistic relationships between bioturbation activities, soil biogeochemical properties, and spatiotemporal heterogeneity, we conducted seasonal correlation analyses. The results demonstrated distinct temporal patterns in soil property responses to grazing and zokor disturbances. During the early grazing season (July), grazing disturbance exhibited significant positive correlations with TN (r = 0.42, p < 0.01), SBD (r = 0.38, p < 0.05), and pH (r = 0.31, p < 0.05), along with a weak positive association with SOC (r = 0.18, p = 0.08) and negative correlation with TIC (r = -0.35, p < 0.01). These patterns indicate that sustained grazing pressure promotes SOC accumulation trends while suppressing TIC formation, concurrently enhancing nitrogen retention and increasing soil compaction and alkalinity. In contrast, plateau zokor disturbance showed negative correlations with TIC (r = -0.29, p < 0.05) and marginal negative associations with SOC (r = -0.15, p = 0.12) and TN (r = -0.17, p = 0.09), but no significant relationships with SBD or pH, suggesting limited negative impacts on soil nutrient pools. Soil depth emerged as a key explanatory variable, displaying negative correlations with SOC (r = -0.61, p < 0.001), TN (r = -0.54, p < 0.001), SBD (r = -0.33, p < 0.01), and pH (r = -0.27, p < 0.05), but positive correlation with TIC (r = 0.58, p < 0.001), confirming the characteristic vertical stratification of these parameters. The post-grazing season (October) revealed modified interaction patterns. Grazing maintained positive correlations with TN (r = 0.39, p < 0.01), SBD (r = 0.35, p < 0.05), and pH (r = 0.29, p < 0.05), though the SOC association weakened (r = 0.12, p = 0.21) while TIC suppression intensified (r = -0.41, p < 0.001). Notably, zokor disturbance exhibited a seasonal reversal in nutrient relationships, developing weak positive correlations with SOC (r = 0.22, p < 0.05) and TN (r = 0.19, p < 0.05) alongside persistent TIC suppression (r = -0.32, p < 0.01). This temporal shift suggests that following the monsoon-induced low activity period, zokor burrowing transitions to facilitating carbon and nitrogen accumulation in mid-shallow soil layers (0-20 cm). Depth-dependent patterns remained consistent with July observations, though correlation magnitudes varied, reflecting seasonal modulation of vertical nutrient gradients. The integrated analysis demonstrates that grazing exerts consistent directional effects on soil compaction and alkalinity while exhibiting temporally variable influences on carbon and nitrogen dynamics. Zokor disturbance displays contrasting seasonal roles, initially depleting surface nutrients during peak activity but subsequently promoting their accumulation. Both bioturbation types significantly influence TIC turnover, though through distinct mechanisms. While seasonal and depth-related factors contribute to observed variability, bioturbation emerges as the predominant driver of soil property modifications, with grazing effects showing greater temporal persistence compared to the phase-dependent impacts of zokor activity. These findings highlight the complex interplay between biotic disturbances and abiotic factors in shaping soil biogeochemical heterogeneity across spatial and temporal scales. Figure 4 Correlation characteristics of soil factors in July and October. The lower left triangle (blue series) shows the correlation characteristics of soil factors in July; the upper right triangle (red series) shows the correlation characteristics of soil factors in October. Statistical significance is denoted as follows: * for p < 0.05, ** for p < 0.01, and *** for p < 0.001. Discussion The equilibrium of soil carbon pools in alpine meadow ecosystems emerges from complex interactions between physical disturbances and coupled biogeochemical processes. Our results demonstrate that livestock-mediated mechanisms (excretion and trampling), plateau zokor bioturbation, and plant litter decomposition collectively drive carbon cycling dynamics, with spatiotemporal heterogeneity in fixed effects—particularly vertical nutrient stratification and seasonal variability—exerting critical regulatory control over carbon pool stability (Figure 5). Figure 5 Path model of the effects of grazing and zokor biological disturbance on soil properties. ”The arrow values are standard path coefficients; R² represents the variable variance explanation rate.;Statistical significance is denoted as follows: *** for p < 0.001, ** for p < 0.01, * for p < 0.05”. The study reveals that biotic disturbances serve as primary drivers of carbon and nitrogen accumulation patterns, vertical redistribution, and modifications to soil pore structure (as reflected in SBD variations), while exhibiting negligible influence on soil pH. This observed pH stability likely stems from the robust carbonate buffering system characteristic of alpine meadow soils. Under persistent low-temperature conditions, the dissolution kinetics of total inorganic carbon (TIC) remain constrained, and the cumulative inhibitory effects of grazing and zokor activities on TIC pools do not surpass the soil’s intrinsic buffering capacity. Furthermore, the inverse SOC-TIC relationship may contribute to pH stabilization through ion exchange equilibria (Henneron et al., 2022), creating a self-regulating mechanism that maintains soil chemical stability despite biotic perturbations. Of particular ecological significance are the differential responses of key soil parameters to disturbance regimes. TN and SBD—exhibiting strong sensitivity to biotic disturbances—interact synergistically with the fixed effects of vertical nutrient distribution and seasonal dynamics to govern carbon pool characteristics. These findings underscore that while biotic factors dominate short-term carbon and nitrogen redistribution, their ultimate impacts on ecosystem-scale carbon storage are modulated by the underlying spatiotemporal framework of soil development processes. The hierarchical control of these factors explains the remarkable resilience of alpine meadow carbon pools despite continuous disturbance pressures, highlighting the need for process-based models that incorporate both biotic and abiotic drivers when predicting carbon cycling responses to environmental change. Seasonal grazing disturbances (trampling/excretion) enhance soil C-N sequestration patterns Grazing disturbances significantly modified soil carbon (C) and nitrogen (N) stocks while increasing (SBD, demonstrating a strong linkage between biotic activity and soil biogeochemistry. Notably, the stoichiometric balance of C and N played a pivotal role in regulating SOC accumulation, with grazing-induced shifts in TN driving long-term C sequestration patterns. Our findings revealed that TN levels were consistently elevated across soil depths in grazed plots, primarily due to sustained organic N input from livestock excreta, which undergoes gradual mineralization into plant-available forms. Additionally, herbivory accelerated the breakdown of high C:N-ratio plant litter, releasing labile N into the soil and further elevating TN. This N enrichment stimulated microbial anabolic efficiency, leading to greater microbial biomass accumulation and subsequent SOC formation through metabolic byproducts (Cotrufo et al., 2013; Liang et al., 2017). Conversely, elevated TN suppressed decomposer activity via stoichiometric constraints, inhibiting TIC formation and reducing mineralization rates (Treseder., 2008; Zamanian et al., 2016). However, the SOC-promoting effects of grazing diminished post-season, likely due to reduced litter input from impaired plant regrowth (Jiang et al., 2020), highlighting the transient nature of grazing-induced C sequestration. Beyond biogeochemical effects, grazing-induced soil compaction (SBD increase) exerted a profound influence on C-N dynamics. Livestock trampling significantly enhanced SBD, particularly in deeper soil layers, reducing micropore availability and restricting oxygen diffusion. This physical restructuring suppressed microbial activity, slowing C and N turnover and promoting long-term sequestration in subsoil horizons. The combined effects of TN-mediated C stabilization and trampling-induced compaction created a synergistic feedback loop—altered pore structures further constrained extracellular enzyme activity, reinforcing C-N coupling in deeper soils (Cotrufo et al., 2013; Rumpe & Kögel-Knabner, 2011). Importantly, grazing impacts exhibited spatiotemporal heterogeneity, reflecting variations in pasture utilization intensity and seasonal transitions. These findings underscore that grazing disturbances operate through intertwined biogeochemical and physical pathways, with stoichiometric regulation, microbial activity, and soil structure collectively shaping C-N sequestration patterns in alpine meadows. Seasonal plateau zokor disturbances (reverse mixing) reshape vertical C-N distribution In contrast to grazing disturbances, plateau zokor activities exhibit pronounced spatiotemporal heterogeneity in their impacts on soil carbon and nitrogen dynamics. Their foraging and burrowing behaviors fundamentally restructure the vertical stratification of TC and TN, while simultaneously modifying SOC and TIC composition and reducing SBD. During the rainy season, when zokor activity is minimal, disturbances predominantly enhance SOC, TC, and TN accumulation in shallow soils (0-10 cm) while decreasing TIC. This pattern emerges as heavy rainfall infiltrates deep nests through shallow burrows, creating waterlogged conditions that restrict zokor activity to aerated surface layers. Consequently, plant root residues and metabolic excreta accumulate near the surface, elevating organic matter inputs and C-N stocks. Concurrently, intense leaching through burrow channels promotes CaCO₃ dissolution, further suppressing TIC formation (Keiluweit et al., 2017). The resulting high moisture content also limits oxygen diffusion, inhibiting aerobic microbial mineralization of SOC and thereby enhancing its retention. In the post-rainy season, when zokor activity peaks, their disturbances induce a distinct reverse mixing phenomenon that vertically redistributes C and N pools (Clark et al., 2016). Burrowing disrupts natural soil stratification, incorporating organic-rich surface materials (e.g., feces and plant debris) into deeper mineral layers (20-30 cm). This process rapidly enriches deep SOC while simultaneously slowing TIC mineralization. Fresh carbon inputs from excretal deposits in deep nests stimulate microbial activity in typically quiescent subsurface soils (Yu et al., 2017). However, the accompanying reduction in SBD improves soil aeration, which may paradoxically accelerate organic matter decomposition and carbon loss via oxidation (Chuan et al., 2020), explaining the observed SOC decline and partial TIC recovery during peak disturbance periods. These findings demonstrate that zokor disturbances drive complex, seasonally dependent shifts in soil C-N dynamics through bioturbation-mediated mechanisms. The interplay between soil physical restructuring, moisture regimes, and microbial activity ultimately governs vertical C-N redistribution patterns, providing novel insights into biogeochemical cycling in alpine meadow ecosystems. Interactive coupling of disturbances (zokor × grazing) drives nonlinear dynamics in soil carbon accumulation Our results demonstrate that grazing and plateau zokor ( Eospalax baileyi ) disturbances interact through complex seasonal dynamics to shape soil carbon pools in alpine meadows (Figure 6). While their combined effects on soil bulk density (SBD) and pH exhibited simple additive patterns, significant non-additive interactions were observed in their impacts on inorganic carbon (TIC), total carbon (TC), soil organic carbon (SOC), and total nitrogen (TN) dynamics. The most substantial interaction occurred in TIC dynamics: grazing and zokor activity synergistically suppressed carbonate accumulation, with the combined inhibitory effect exceeding the sum of individual impacts (Σindividual effects). This amplification likely stems from grazing-induced soil compaction physically constraining zokor excavation efficiency, thereby limiting upward mixing of calcium carbonate-rich subsoil material (Yu et al., 2017). Conversely, the disturbances exhibited antagonism in organic carbon accumulation—while either disturbance alone promoted TC and SOC accumulation, their combined effect was sub-additive. This suggests microbial processing capacity limitations may impose an upper threshold on carbon sequestration despite stable community composition (Han et al., 2016). Similarly, non-additive TN dynamics emerged where zokor burrow systems physically intercepted nitrogen and activated denitrifying microorganisms, partially offsetting the nitrogen enrichment from livestock excreta under grazing, yielding a net nitrogen increase below additive expectations (Wang et al., 2019). Figure 6 Non-additive effects of the interaction between grazing and zokor bioturbation on soil carbon and nitrogen properties in alpine grasslands. Statistical significance is denoted as follows: ***for p < 0.001, **for p < 0.01, *for p 0.05; negative values on the vertical axis represent the antagonistic zone, and positive values represent the synergistic zone. Negative/positive values on the horizontal axis correspond to the direction of the effect; the size of the points indicates the magnitude of the effect value (|β| value). Conclusion This study demonstrates that grazing and plateau zokor disturbances exert distinct yet interconnected influences on soil carbon dynamics in Qinghai-Tibetan alpine meadows. Grazing enhanced SOC and TN stocks through organic matter input and compaction-induced stabilization while suppressing TIC via pH-mediated dissolution. Meanwhile, zokor activity drove seasonal carbon redistribution, with surface accumulation during the growing season and subsoil enrichment post-grazing, reflecting their unique “reverse mixing” effect. Critically, their combined impacts were non-additive—synergistically boosting TN accumulation but antagonistically limiting SOC gains, likely mediated by microbial mineralization thresholds under conditions of elevated bulk density. From a management perspective, these findings suggest that moderate grazing (≤10 sheep units/ha) coupled with strategic zokor activity zone preservation could optimize carbon sequestration by balancing surface organic inputs with deep carbon stabilization. Seasonal protection of zokor-modified surface soils (0-10 cm) during peak activity periods (July) may further enhance their ecological engineering function. However, the exacerbated TIC loss under combined disturbances underscores the need for targeted monitoring in calcareous soils, where inorganic carbon depletion could impair long-term buffering capacity. Our work introduces a novel “disturbance co-management” framework for alpine grasslands, elucidating how keystone ecosystem engineers (e.g., plateau zokors) and anthropogenic activities jointly regulate soil carbon persistence. 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Effects of livestock grazing on grassland carbon storage and release override impacts associated with global climate change[J]. Global Change Biology, 25(3):1119-1132. doi:10.1111/gcb.14533 Supplementary Material File (image2.emf) Download 358.76 KB File (image4.emf) Download 562.43 KB File (table 1.xlsx) Download 10.44 KB File (table 2.xlsx) Download 11.37 KB Information & Authors Information Version history V1 Version 1 04 August 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords alpine meadow biotic disturbance non-additive effect soil organic carbon structural equation modeling Authors Affiliations Yang Yang XiZang University View all articles by this author Rui Mao Xiaojin County Forestry and Grassland Bureau View all articles by this author Huankun Leng Southwest Minzu University View all articles by this author Yi Huang XiZang University View all articles by this author Jianmin Yao Ganzi Tibetan Autonomous Prefecture Grassland Work Station View all articles by this author Tingyong Yang Ganzi Tibetan Autonomous Prefecture Grassland Work Station View all articles by this author Hong Jin Sichuan University College of Life Sciences View all articles by this author Jian Yang [email protected] Southwest Minzu University View all articles by this author Metrics & Citations Metrics Article Usage 230 views 134 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Yang Yang, Rui Mao, Huankun Leng, et al. Grazing and Plateau Zokor Disturbance Exert Non-additive Effects on Soil Carbon Pools in Alpine Meadows of the Qinghai-Tibet Plateau. Authorea . 04 August 2025. DOI: https://doi.org/10.22541/au.175431802.26306317/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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