Global aridification threatens dryland ecosystems biodiversity and stability, yet the influence of multidimensional biodiversity on stability across aridity gradients is complex and context-dependent. Here we analyze plant and soil microbial diversity (taxonomic, phylogenetic, functional) across a 3,000-kilometer aridity gradient on the Mongolian Plateau and use multi-year observations from two validation sites. We identify a critical aridity threshold (Aridity ≈ 0.83) where stability mechanisms abruptly shift. Below this threshold (less arid conditions), ecosystem stability is positively linked to plant and fungal taxonomic richness. Above it (more arid conditions), stability correlates with conservative plant traits (lower special leaf area) and lower phylogenetic diversity, reflecting environmental filtering for stress-tolerant species. This transition is driven by a shift from C3 to C4 plant dominance, altering community traits and plant-microbial interactions. While our correlational findings require experimental confirmation, they challenge linear stability models, highlighting the importance of threshold-dependent biodiversity-environment interactions for dryland management. Ecosystem stability shifts at an aridity threshold where in less arid conditions it is linked to plant and fungal richness and in more arid conditions it depends on conservative plant traits and lower phylogenetic diversity, based on sampling across a 3000-km Mongolian Plateau gradient.

Livestock grazing affects ecosystems through vegetation consumption, trampling and dung deposition. However, while numerous studies have examined the combined effects of grazing on plant and soil biota community attributes (CAs) as well as ecosystem multifunctionality and their stability, the independent role of dung deposition has remained unclear. This knowledge gap limits our ability to predict how individual components of grazing shape ecosystem multifunctional stability. By conducting a long-term sheep dung deposition experiment with 9 gradients in Mongolian grasslands, while sheep dung deposition altered plant and soil biota groups, its effect on the CAs and stability of plants (indicated by all 3 CAs and 2 stability of CAs) was significantly greater than that on microorganisms (indicated by only 1 CA and 1 stability of CA) and nematodes (indicated by only 1 CA) along the deposition gradient. Furthermore, both ecosystem multifunctionality (from 0.329 to 0.529, r = 0.771, p < 0.001) and its temporal stability (from 4.018 to 6.965, r = 0.430, p < 0.01) increased with the gradient of increasing sheep dung deposition. More importantly, our piecewise structural equation modeling and linear regression showed that the stability of plant and soil microbial CAs was the primary driver of ecosystem multifunctional stability, with this effect largely attributable to the stability of plant (r = 0.321, p < 0.05) and soil microbial community composition (r = 0.423, p < 0.01) rather than the stability of their diversity (p > 0.05). Our findings reveal that compositional stability represents a critical yet underappreciated dimension of ecosystem stability, which suggests that nutrient input from dung deposition serves as a key stabilizing mechanism in grazing systems. This new perspective emphasizes the importance of maintaining stable community composition to sustain the ecosystem multifunctional stability under anthropogenic nutrient enrichment, with important implications for grassland management and conservation.

Grazing by large herbivores is a critical factor shaping grassland biodiversity and ecosystem functioning worldwide, yet its consequences for soil communities remain poorly understood. This gap is important because soil food webs underpin ecosystem processes and may respond differently to grazing depending on herbivore identity and local heterogeneity (i.e. patchiness). Here, a four‐year field experiment was conducted to investigate the influences of cattle and sheep grazing on soil nematode communities in a grassland that features a mosaic of degraded high‐salinity and undegraded low‐salinity patches. We focus on nematode communities because nematode‐based indices offer key insights into the structure of the soil food web and overall soil health. In the absence of grazing, degraded patches exhibited a more simplified soil food web structure, indicated by reduced nematode diversity, maturity index and structure index, but higher nematode biomass and energy flux compared to undegraded patches. However, sheep grazing reduced total nematode biomass and energy flux in degraded patches, while cattle grazing decreased the biomass of higher trophic levels (i.e. omnivores and predators), the energy flux from lower to higher trophic levels and flow uniformity in undegraded patches. These effects resulted from declines in the abundance of large‐bodied nematodes, primarily limited by soil pore space and soil microbial biomass. Collectively, our findings demonstrate that livestock grazing can exacerbate soil degradation by inhibiting soil fauna communities, but the outcomes are patch‐ and herbivore‐specific. By combining nematode structural and functional indices, our study advances understanding of how herbivore identity interacts with fine‐scale grassland heterogeneity to regulate soil food webs. This framework provides a new pathway for linking grazing management to soil health, offering a scientific basis for adaptive policies that balance production goals with sustainable grassland restoration under environmental change. Read the free Plain Language Summary for this article on the Journal blog.

Abstract The number of co‐occurring global change factors (GCFs) is increasing, yet their combined effects on grassland functioning via plant–soil biotic interactions remain poorly understood, especially under contrasting precipitation contexts. Using a long‐term multifactor experiment in the semi‐arid steppe of Inner Mongolia, we established a gradient in GCF number (0–3) through nitrogen addition, phosphorus addition and soil acidification. By integrating plant diversity with the taxonomic, functional and metabolic dimensions of nematode communities, we evaluated their effects on above‐ground net primary productivity (ANPP) and below‐ground ecosystem multifunctionality (BEMF) and tested whether these relationships were reorganized under contrasting precipitation years. Increasing GCF number consistently reduced plant and nematode diversity, simplified nematode food‐web structure and suppressed nematode metabolic activity. ANPP increased with GCF number only in the wet year, whereas BEMF declined in both years. ANPP was primarily and positively associated with nematode metabolic footprints, whereas BEMF was jointly regulated by plant diversity and nematode metabolic footprints. Importantly, these pathways shifted with precipitation context. In the normal year, plant diversity and nematode metabolic footprints jointly sustained both ANPP and BEMF. In the wet year, a functional divergence emerged: above‐ground processes benefited from nutrient inputs, increasing ANPP, whereas below‐ground processes experienced cumulative stress from multiple GCFs, suppressing nematode metabolic footprints and reducing BEMF. Synthesis and applications . Our findings demonstrate that the number of co‐occurring GCFs is a critical but underappreciated dimension of global change, and its ecological consequences depend strongly on precipitation context. Grassland management should consider cumulative nutrient and acidification pressures, maintain plant diversity and use nematode metabolic footprints as indicators of below‐ground functional change. Incorporating soil faunal functional traits into global change assessment frameworks is therefore essential for understanding and sustaining ecosystem multifunctionality under future environmental change.

Soil parasitic protists influence the health of plants and soil organisms. Yet, the extent to which these interactions impact the stability of terrestrial ecosystems remains largely unquantified. Here, we utilized two independent global-scale biodiversity surveys available online to investigate the relationship between the taxonomic diversity of parasitic protists and satellite-based time series of ecosystem productivity (i.e., normalized difference vegetation index). We found that soil parasitic protist diversity, particularly the diversity of Apicomplexa (common parasites of soil invertebrates), was consistently and positively correlated with ecosystem temporal stability worldwide. Our analyses suggest that Apicomplexa diversity is positively associated with temporal stability of ecosystem productivity by boosting mean productivity, likely through regulating invertebrate plant herbivory and nutrient cycling. Furthermore, the relationships between Apicomplexa diversity and ecosystem temporal stability were strongly mediated by climate, with a stronger correlation found in less productive colder or drier ecosystems. Our findings provide large-scale empirical evidence for the previously undescribed significant statistical relationship between soil parasitic protist diversity and ecosystem stability, highlighting their potential role in explaining the stability of terrestrial ecosystems globally.

Abstract Grassland degradation poses a severe threat to semi-arid ecosystems. However, the interactive effects of litter management and nitrogen (N) enrichment on ecosystem stability remain unclear, especially when jointly considering above- and belowground processes. We coupled N enrichment with a seven-year asymmetric litter manipulation experiment in Inner Mongolian grasslands. Over three consecutive years, we assessed how these drivers influenced plant and soil biodiversity and the stability of above- and belowground multifunctionality. In the undegraded grassland, both litter removal and N enrichment reduced bacterial diversity and belowground functionality, yet whole-system stability remained largely unchanged. In the degraded grassland, however, N enrichment reduced belowground functional stability by simplifying soil communities and amplifying functional variability, whereas litter addition buffered these destabilizing effects, consistent with improved moisture retention. Notably, soil biodiversity, rather than plant diversity, emerged as the primary biotic regulator of stability, but the dominant stabilizing taxa shifted with grassland state: nematode and bacterial diversity underpinned stability in the undegraded and degraded grassland, respectively. Above- and belowground stability were decoupled, with belowground processes exhibiting greater sensitivity to both litter and N manipulation. Consequently, management for stability in semi-arid grasslands should explicitly prioritize soil biodiversity over plant diversity alone. In undegraded systems, minimizing litter removal better safeguards belowground functioning. In degraded systems, strategic litter addition enhances resistance to N enrichment by alleviating moisture limitation but continued N inputs risk long-term destabilization via soil biotic homogenization. Monitoring soil bioindicators (e.g., nematode trophic diversity and functional bacterial groups) can provide early warnings and guide adaptive management strategies.

The partitioning of biodiversity effects into selection and complementarity effects has substantially advanced our understanding of biodiversity–ecosystem functioning relationships. While this framework is well established for plant communities, its extension to soil biota remains underexplored, limiting our understanding of how plant diversity influences ecosystem multifunctionality via belowground pathways. Here, we integrate a three-year monoculture experiment with surveys of naturally assembled plant communities to evaluate how plant diversity shapes soil biotic attributes and ecosystem multifunctionality. Across bacteria, fungi, and nematodes, net diversity effects on soil biota were largely accounted for by complementarity effects, whereas selection effects were generally weak.Notably,selection effects of plant diversity on soil biotic diversity and biomass were associated with ecosystem multifunctionality in contrasting ways, while complementarity effects, particularly those observed for bacterial biomass, were positively related to multifunctionality. Our results indicate that plant diversity is consistently associated with higher ecosystem multifunctionality, a relationship that corresponds strongly with belowground complementarity effects expressed in soil biotic biomass, highlighting the importance of resource partitioning and facilitative interactions in soil communities. We also highlight that these inferences rely on integrating experimental monocultures with observational natural communities and thus represent strong statistical associations rather than direct experimental manipulations of soil biota.

Subsoils store the majority of terrestrial organic carbon, yet the stability of this vast reservoir under climate change remains a critical uncertainty. In this study, we investigated soil profiles across a continental-scale aridity gradient on the Mongolian Plateau to assess the vulnerability of deep soil carbon fractions. Our results reveal that subsoil mineral-associated organic carbon (MAOC), traditionally considered a stable sink, is surprisingly more sensitive to increasing aridity than the labile particulate organic carbon (POC) fraction. Structural equation modeling links this unexpected vulnerability to a fundamental vertical shift in carbon stabilization controls. Unlike topsoils, which are closely linked to abiotic variables, subsoil carbon stability is primarily correlated with microbial community attributes, specifically microbial biomass and fungal diversity. This suggests that subsoil carbon storage is a biotically mediated process highly responsive to environmental stress. We conclude that current conceptual models, which often assume the universal kinetic persistence of MAOC, may critically underestimate the potential for carbon loss from deep dryland soils, posing a risk of positive carbon-climate feedbacks as drylands expand globally.

Theory and observation suggest that single-dimensional plant attributes and diversity may play a key role in explaining variation in soil biodiversity, but the empirical evidence in this area is still lacking considering multiple functional groups in soil biota. In this study, we explore the associations between plant taxonomic, phylogenetic, and functional diversity and soil biodiversity of multiple functional groups, as well as ecosystem functions in both monoculture and natural grasslands. We identified multidimensional plant attributes that could be categorized into three dimensions related to plant productivity, nutrient levels in leaves and roots, and phylogenetic relationships. We found that multidimensional plant attributes and soil properties commonly explained the biomass, richness and composition of soil biota across multitrophic levels, but this varied with the types of communities and their functional groups in both monoculture and natural grasslands. For example, plant functional traits or phylogeny explained more variation in soil fungi than in soil bacteria. Additionally, some links between multidimensional plant attributes and soil biota and soil functions were similar in both monoculture and natural grasslands, but there were weak effects of soil bacteria in the natural grassland and consistent strong effects of soil fungi in both monoculture and natural grasslands. This study provides experimental evidence supporting the effect of plant taxonomic, phylogenetic, and functional traits on shaping soil biodiversity and functions, which are crucial for understanding how plant-soil interactions may be impacted by ongoing global environmental changes.

Litter decomposition is a key process influencing soil carbon and nitrogen mineralization rates (Cmin and Nmin). Although numerous studies have investigated the factors affecting litter decomposition, how litter traits, decomposition time, soil properties, and microbial communities collectively affect Cmin and Nmin across different decomposition stages remains poorly understood. Here, we conducted a microcosm incubation experiment under controlled indoor conditions, using leaf and root litter from four dominant plant species (Cleistogenes squarrosa, Stipa capillata, Leymus chinensis, and Agropyron cristatum) in a typical steppe of Inner Mongolia. We aimed to examine the effects of litter type (leaf vs. root), species richness (1, 2, 4 species), and species identity (11 treatments from 4 dominant species) on soil Cmin and Nmin at different decomposition stages. Our results showed that litter type and decomposition stage had significant interactive effects on both Cmin and Nmin. Species richness showed no significant interaction with decomposition time, whereas the litter identity exhibited a significant interaction with decomposition stage, indicating that species identity was more strongly associated with variation in Cmin and Nmin than species richness. Structural equation modeling revealed distinct predictive relationships: Cmin was most strongly associated with microbial biomass, whereas Nmin was co-associated with litter traits, soil properties, and microbial biomass. As the incubation period progressed, the overarching predictors for both leaf and root litter Cmin and Nmin gradually declined in number and explanatory power. Collectively, these findings suggest that incorporating litter identity and decomposition stage may improve predictions of soil carbon and nitrogen dynamics in grassland ecosystems.

Understanding the mechanisms driving ecosystem stability across trophic levels is essential for sustaining ecosystem services. However, the temporal trajectories of plant and soil microbial stability under combined global change factors, and whether they diverge along grazing-induced environmental gradients, remain poorly resolved. Using an 8-year field experiment in Inner Mongolian grasslands with prior 7-year grazing treatments (light, moderate, heavy), we analyzed the data across five consecutive, moving temporal windows (2012-2015, 2013-2016, 2014-2017, 2015-2018, and 2016-2019) and manipulated water (+30% precipitation) and nitrogen (+10.5 g N m-2 yr-1) addition. Under historically light and moderate grazing, plant stability increased while microbial stability decreased, yet both exhibited similarly unchanged dynamics under heavy grazing. Resource addition reduced both stabilities mainly in light and moderate grazed systems, though effects weakened over time. This reduction occurred through weakened compensatory or statistical-averaging effects within plant and microbial functional groups. Plant stability was primarily driven by statistical-averaging effect among plant functional groups, whereas microbial stability was more strongly predicted by compensatory effect. Notably, statistical-averaging effect in soil microbial groups enhanced plant stability by stimulating plant functional group stability. Trophic asynchrony between plant and microbial groups impaired both stabilities by reducing their respective compensatory or statistical averaging effects. Our findings reveal that plant and microbial stability respond to global changes in trophic-level-specific and context-dependent ways, governed by distinct and temporally shifting biotic mechanisms. This highlights the need to integrate historical land use, plant-soil interactions, and their temporal dynamics for predicting and managing future ecosystem services.

The role of fertilization diversity (the variety of nutrient types added) in modulating the effects of extreme drought on multi-trophic communities and their functions remains a critical unknown in ecology. We conducted a multi-nutrient factorial experiment (control, N, NP, and NPK additions) under simulated extreme drought in an alpine meadow on the Qinghai-Tibetan Plateau. We assessed the responses of soil abiotic properties, plant communities, soil microbial (bacteria and fungi) and nematode communities, and ecosystem multifunctionality (EMF). Our results reveal that fertilization diversity induces a trophic asymmetry in ecosystem responses to drought: increasing fertilization diversity (and total nutrient load) significantly altered the response of the plant community to drought by promoting the competitive dominance of drought-tolerant grasses, which in turn modulated ecosystem function of aboveground net primary productivity. Conversely, fertilization diversity amplified the negative effects of drought on soil bacterial and fungal biomass, likely due to exacerbating microbial carbon limitation. For soil nematodes, fertilization diversity modified the response of community composition to drought and simplified nematode communities. Consequently, despite these compensatory and contrasting responses across trophic levels, fertilization diversity led to a net decline in EMF under drought. This net loss occurred because the positive contributions from the plant pathway were decisively outweighed by the substantial suppression of microbial processes, revealing a fundamental decoupling between above- and below-ground components. Our findings demonstrate that the balance and diversity of nutrient inputs, rather than nitrogen dose alone, is a critical factor modulating ecosystem responses to drought, creating contrasting responses across trophic levels that necessitate a holistic, multi-trophic perspective for effective ecosystem management under global change.

The increase in phosphorus (P) and nitrogen (N) inputs, as well as soil acidification resulting from multiple environmental changes, has profound effects on the attributes of plant and soil biota communities, and on ecosystem functions. However, how these community attributes impact ecosystem multifunctionality (EMF) and its stability under multiple environmental changes remains unclear. By integrating datasets over four consecutive years from an experiment with enrichments of soil acidification and N and P in a semiarid grassland on the Mongolian Plateau, we explored the effects of environmental changes on community attributes (species richness, asynchrony, and compositional temporal stability) of plants and soil biota (bacteria, fungi, and nematodes) and their associations with EMF stability. The attributes of plants and soil biota showed opposite responses to nutrient enrichment under soil acidification and non-acidification conditions. Soil acidification had a more significant effect on the community attributes of plants and soil biota, as well as on the components of EMF stability, than nutrient enrichment. Soil acidification decreased both the mean and stability of EMF, while N enrichment increased the mean of EMF. P did not have a significant effect on the components of EMF stability, but N and P showed positive interactive effects on the mean and stability of EMF. We also found that plant and soil biota richness had a positive effect on EMF, while plant asynchrony and soil biota compositional stability determined EMF stability. The community attributes of plants and soil biota co-regulate the components of EMF stability under multiple environmental changes. These findings highlight the urgent need to protect the biodiversity of plants and soil biota to maintain EMF and its stability, especially for ecosystems undergoing multiple environmental changes.

Studies have determined that soil biota have distinct responses to plant richness. However, the potential mechanisms that regulate soil biota (microbes and fauna) attributes (biomass, activity, and abundance) to plant mixtures over experimental time are still unclear. By conducting 1594 paired observations of the impacts of plant mixture on soil biota attributes and its corresponding potential drivers from 179 studies, we found that plant above- and belowground biomass and total biomass were significantly increased by 35.0%, 52.9%, and 48.6% under plant mixture, respectively. Soil pH decreased significantly by 0.8% with experimental time. The responses of soil microbial attributes were more sensitive than soil fauna abundances under plant mixture over time. On average, soil microbial respiration and microbial biomass increased by 11.6% and 12.1%, respectively, in plant mixtures across all ecosystem types. For soil fauna community, only the abundance of herbivores showed a significant increase of 20.4% to plant mixtures. The response of above- and belowground biomass, total biomass, the ratio of carbon to nitrogen, and pH showed positive relationships with most specific microbial attributes, while mean annual precipitation, mean annual temperature, and the response of soil total nitrogen and NO3–-N showed negative relationships with them in response to plant mixtures. The abundance of soil fauna was secondarily affected by the changes of soil abiotic properties. Taken together, the response of soil total carbon had a strong effect on soil biota attributes. Changes in belowground biomass and total biomass showed negative relationships with specific soil fauna abundance, while soil total carbon, nitrogen, pH, and soil moisture showed positive relationships with specific soil fauna abundance. However, only herbivore abundance showed significant differences across different ecosystems. Our analysis illustrates the distinct responses of soil biota attributes to plant mixtures and their potential influencing factors, thereby benefiting the sustainability of soil biota biodiversity in the face of plant richness loss.

Habitat fragmentation poses significant threats to soil biodiversity and ecosystem stability, yet its impacts on multifunctionality resistance under global change remain unclear. Here, we investigated 61 islands in China’s subtropical Zhelin Lake Reservoir, through experiments simulating multiple stressors, to assess how changes in soil biodiversity induced by habitat fragmentation affect the multifunctionality resistance to nitrogen enrichment, warming, and wetting-drying cycles disturbances. Our results revealed that soil moisture, nematode/protist α-diversity, and multifunctionality resistance (quantified through nutrient cycling stability) declined with fragmentation intensity (from the large to small islands). Nematode α-diversity, particularly bacterivorous taxa, emerged as a keystone mediator, directly enhancing resistance to global change stressors via microbial regulation and nutrient cycling. Conversely, protist β-diversity reduced warming resistance through community destabilization. Structural equation modeling demonstrated dual fragmentation effects: direct moisture-driven functional decline versus indirect biodiversity-mediated stabilization. Stressor-specific mechanisms diverged fungal-nematode synergies buffered nitrogen enrichment impacts, while protist community turnover exacerbated thermal vulnerability. These findings challenge microbial-centric paradigms, highlighting the predominate role of microfauna in regulating soil multifunctionality resistance to global change. Our study highlights that conservation strategies should prioritize preserving larger fragments and soil micro-faunal diversity to sustain multifunctionality under global change, emphasizing the conservation of soil microorganisms such as nematodes and protists in fragmented landscapes.

Increasing the number of global change factors (GCFs) strongly influences biodiversity and ecosystem functions. However, the specific mechanisms through which biodiversity, especially soil biodiversity, stabilise ecosystem multifunctionality under rapidly growing GCFs remain elusive. Here, we implemented a multifaceted approach involving multiple GCFs (nitrogen addition, phosphorus addition and soil acidification) in the Inner Mongolia grassland to elucidate the impact of species diversity, community composition and temporal asynchrony within plant and soil biota on multifunctional stability. Our findings showed that with an increasing number of GCFs, plant and soil biodiversity, ecosystem multifunctionality and multifunctional stability broadly decreased. The negative effects of GCFs on multifunctional stability were primarily associated with the community asynchrony of soil nematodes and plants, while the negative effects on ecosystem multifunctionality were mainly associated with the community composition of soil fungi. Additionally, the indirect influence of diversities within plants and soil biota on multifunctionality and its stability was manifested through their effects on the community composition or asynchrony. Synthesis. Our results provide new empirical evidence that soil biodiversity is at least as important as plant biodiversity in determining multifunctionality and multifunctional stability under multiple GCFs. These findings highlight the importance of conserving soil biodiversity and integrating it into conservation efforts to maintain ecosystem stability in the face of increasing GCFs.

The enrichment of nutrients (e.g. N and P) is crucial in shaping the links between diversity and ecosystem functions. Previous research has mainly focused on how nutrient enrichment affects community diversity and composition within a single trophic level, such as plants or soil microbial communities. However, how nutrient enrichment affects community composition and diversity across multiple trophic levels and ecosystem functions has not been extensively explored. By conducting two long‐term N‐ and P‐enrichment experiments in temperate steppes, we explored the response of diversity and composition at both the community and functional group level across the soil food webs to nutrient enrichment, as well as their relationship with ecosystem functions. We found that the responses of soil biota and plants to nutrient enrichment varied depending on the community and functional group. N‐enrichment resulted in a decrease in plant and bacterial richness at both the community and functional group levels, while P‐enrichment decreased fungal and nematode richness at both levels. In addition, N‐enrichment changed the community composition of plants and all soil biota, while P‐enrichment only affected the community composition of fungi and nematodes. Our findings also showed that community composition across multiple trophic levels played a crucial role in regulating ecosystem functions (e.g. plant biomass, soil biota biomass and SOM decomposition) when considering both community composition and diversity simultaneously. For example, N‐enrichment induced changes in the community composition of plants, bacteria and nematodes, which altered plant biomass, while P‐enrichment induced changes in the community composition of nematodes that altered soil biota biomass and SOM decomposition. Synthesis . Overall, our study suggests that long‐term nutrient enrichment may have a greater impact on community composition than diversity across multiple trophic levels, and these changes in community composition can have broad implications for ecosystem functions. Therefore, more effort should be made not only on community diversity but also on composition to clarify the relationship between diversity and ecosystem functions in future studies under climate change.

Climatic shifts critically regulate soil organic carbon (SOC) dynamics, biodiversity, and productivity in grasslands. However, the mechanisms linking abiotic/biotic factors to plant diversity-SOC mineralization synergies remain unclear. To study this mechanistic relationship, we established 12 sampling sites along an east-west precipitation gradient across the China-Mongolia steppe. We measured plant diversity and biomass for both species and functional groups in 12 grassland sites. In the laboratory, we analyzed soil nutrients and microbial communities. We also measured the SOC mineralization potential using 28-day incubations. The results indicated that: (1) Aboveground biomass (AGB) increased through two opposing strategies, enhancing or reducing plant diversity, with thresholds at Shannon-Wiener indices of 1.14 (arid west) and 2.19 (humid east). AGB shifts altered resource competition and microenvironments, directly impacting diversity. (2) Plant diversity was primarily regulated by soil pH, SOC, and mean annual temperature (MAT). (3) Perennial grasses dominated productivity, while perennial forbs drove diversity via niche complementarity. (4) Microbial biomass carbon (MBC) was the direct driver of SOC mineralization, modulated by mean annual precipitation (MAP) through SOC mediation. (5) SOC mediated contrasting ecosystem effects by suppressing plant diversity through pH-driven nutrient limitations while simultaneously enhancing mineralization rates via stimulation of microbial decomposer activity. SOC properties and precipitation govern divergent changes in grassland diversity and carbon cycling. Strategic management of SOC pools, coupled with precipitation adaptation and biodiversity conservation, can enhance ecosystem resilience under climate change. This mechanistic framework advances understanding of grassland responses to global change.

Soil nematode communities are increasingly subjected to pressures from multiple global change drivers, such as nitrogen (N) enrichment and land management practices. Although the critical role of N inputs in regulating soil nematode communities has been well studied, the contrasting responses of soil nematode diversity to N enrichment in natural versus managed ecosystems remain poorly understood. To address this knowledge gap, we conduct a global meta‐analysis using 3323 paired observations from 173 publications to quantify the impacts of mineral N inputs on the richness and abundance of soil nematode diversity across natural ecosystems (e.g. unmanaged grasslands and forests) and managed ecosystems (e.g. croplands). N enrichment significantly reduced the richness and abundance of soil nematode communities in natural ecosystems, primarily driven by the prohibiting effects of N enrichment‐induced soil ammonium toxicity and soil acidification on the abundances of plant‐feeding, fungal‐feeding and omnivorous‐carnivorous nematodes. In contrast, while N enrichment reduced the taxon richness of soil nematodes in managed ecosystems, it did not diminish their total abundance. This discrepancy may be explained by the increased soil microbial biomass under N enrichment, which favoured the dominance of bacterial‐feeding nematodes. These nematodes thrived at the expense of other trophic guilds with low resource competitiveness and high N sensitivities, leading to a loss of species diversity but maintaining overall community abundance. Furthermore, the responses of soil nematode richness and abundance to N enrichment in managed ecosystems were not regulated by N addition regimes and climate factors. This suggests that management practices may override the constraints imposed by climate change on nematode diversity. Synthesis and application. Our findings demonstrate that N enrichment exerts a greater negative impact on soil nematode diversity in natural ecosystems compared with managed cropping systems, which arises from the distinct responses of different soil nematode trophic guilds to management practices and environmental changes. Understanding the mechanisms underlying the contrasting effects of N enrichment on soil nematode diversity in natural versus managed ecosystems is critical for enhancing the ecological resilience of soil food webs and sustaining soil biodiversity in the face of global change.

Litter decomposition drives grassland biogeochemical cycles, yet the distinct roles of leaf and root litter identity, richness, and functional traits in regulating soil microbial diversity and decomposition remain poorly resolved. Using a 120-day mesocosm experiment with leaf and root litter of the dominant species in Inner Mongolia grassland, we assessed how litter type (leaf vs. root), richness (1, 2, 4 species), and identity (root or leaf litter of 4 dominant species) modulate microbial diversity and soil carbon (C) and nitrogen (N) release. We found that litter type and identity more strongly influenced microbial biomass than species richness, and root litter supported higher bacterial alpha diversity but lower microbial biomass and fungal beta diversity compared to leaf litter. Root litter identity primarily affected the overall beta diversity patterns of both bacterial and fungal communities, while greater leaf litter richness significantly suppressed soil C release. Mechanistically, root litter identity associated with the resource-conservative strategy directly controlled soil C release and indirectly regulated N retention via bacterial beta diversity. Conversely, leaf litter type characterized by the resource-acquisitive strategy primarily affected soil C release by altering microbial alpha diversity, and could also enhance N release by directly increasing soil microbial biomass. Our results underscore the significant influence of litter type, identity, and richness on soil microbial diversity and C and N release, supporting the strategic use of litter identity to modulate C and N release and the enhancement of C sequestration through increased leaf litter richness in grassland restoration efforts.