Grazing affects plant carbon sequestration and nutrient cycles, changing the carbon (C), nitrogen (N) and phosphorus (P) stoichiometry in grassland ecosystems. However, the effects of grazing intensity on fine-root C:N:P stoichiometry in alpine meadows remain unclear. Here, we examine how grazing intensity influences the fine-root C:N:P stoichiometry in Tibetan alpine meadows. We conducted a long-term (9 years) experiment on the effects of four grazing intensities (ungrazed, light, moderate and heavy grazing) on an alpine meadow on the eastern Tibetan Plateau. Light and moderate grazing increased fine-root C and N concentrations and the N:P ratio, but decreased the C:N ratio, whereas heavy grazing had no effect on C:N:P stoichiometry. The fine-root C:N:P stoichiometry differed among the plant functional groups at different grazing intensities. In addition, grazing intensity indirectly affected fine-root C:N:P stoichiometry by changing aboveground biomass (AGB) and soil physicochemical properties. Overall, we found that grazing intensity regulated fine-root C:N:P stoichiometry in alpine meadows by changing AGB and soil physicochemical properties. Our findings have important implications for improving alpine meadow ecosystem protection by implementing sustainable grazing intensities on the Tibetan Plateau.

Forest fires are key ecological disturbances that influence vegetation dynamics and soil microbial processes central to carbon and nutrient cycling. While fire frequency and severity are increasing globally, the microbial mechanisms underlying ecosystem recovery remain inadequately understood. We used high-throughput amplicon sequencing to evaluate short-term effects of low- and high-severity fires on soil microbial diversity and co-occurrence networks following fire disturbance in a temperate forest. Fire severity had no significant impact on microbial α-diversity, but significantly altered β-diversity. Mantel tests indicated that soil pH and belowground biomass were the primary environmental drivers of bacterial and fungal community turnover under different fire severities. Further, network analyses revealed distinct microbial responses to fire severity: low-severity fire primarily restructured bacterial associations, whereas high-severity fire disrupted both bacterial and fungal networks. These findings suggest that microbial community structure and interactions are differentially sensitive to fire severity, with implications for soil functional resilience and ecosystem restoration strategies in fire-affected forests.

Environmental changes, especially climate variability, can substantially influence phenological patterns of plants and their associated insect communities, potentially reshaping the spatial distribution of their interactions. Despite considerable attention on species range shifts under climate change, empirical studies explicitly addressing how these shifts affect spatial matching between plants and their associated insect communities remain scarce. Here, we investigated inter-annual changes in the spatial matching between the poisonous weed Stellera chamaejasme L. and its associated floral visitor community along an altitudinal gradient over two climatically distinct growing seasons in the Qilian Mountains, China. We monitored the flowering phenology of S. chamaejasme and the abundance of its major pollinators (Meloidae, Tachinidae, Scarabaeidae and Noctuidae) at different altitudes. Our findings show a pronounced altitudinal displacement between the peak abundance zones of S. chamaejasme and its major pollinators, indicating spatial mismatches in both years (2021 and 2022). However, the increased preseason thermal accumulation in 2022 improved spatial matching, as high-density overlap zones shifted to higher altitudes, where insect visitation rates also increased. Additionally, the elevated preseason heat significantly advanced flowering phenology at high altitudes, which may contribute positively to breaking the altitudinal distribution limits of S. chamaejasme, along with enhanced spatial matching with pollinators. This study highlights the significant impact of inter-annual climate variability on spatial matching between mountain plants and pollinators at various altitudes, which is crucial for improving population dynamics models and enhancing the accuracy of predictions.

Mixed cultivation of Larix gmelinii and Juglans mandshurica is a typical strategy for increasing stand productivity in Northeast China. However, the adaptive strategies of fine roots and root-associated fungi (RAF) after mixed cultivation remain unclear. Here, we examined the chemical, morphological and anatomical characteristics of fine roots, along with the composition, diversity and co-occurrence network structure of their RAF communities. Our results showed that mixed cultivation increased the root diameter and root tissue density of first-order to third-order fine roots for both L. gmelinii and J. mandshurica but decreased the specific root length. The root economic spectrum of the two species demonstrated a shift from a ‘do-it-yourself’ strategy to an ‘outsourcing’ strategy in their first- and second-order roots after mixed cultivation. Arbuscular mycorrhizal fungi and endophytic fungi were the main fungal functional groups within the RAF of J. mandshurica, while ectomycorrhizal fungi were dominant in those of L. gmelinii. Mixed cultivation increased the RAF alpha diversity of J. mandshurica but decreased the RAF alpha diversity of L. gmelinii. Negative correlations in the co-occurrence networks of the RAF communities accounted for >50% of the two species, indicating that competitive relationships dominated within the RAF community. Changes in the composition of RAF after mixed cultivation effectively supported shifts in the root economic spectrum of the two species. The coordinated changes in fine root systems and their associated mycorrhizal fungi enable the two species to maintain their competitive edge in nutrient absorption when they are planted together.

Leaf economic, hydraulic and anatomical traits play crucial roles in plant adaptation to diverse and variable environments. However, their relationships at the intraspecific level remain unclear. In this study, we investigated Quercus variabilis, a species spanning temperate to subtropical zones, to assess functional trait variation along a north-to-south environmental gradient in China (24°94′–40°26′ N). We analyzed 10 key functional traits, including leaf mass per area (LMA), leaf thickness (LT), leaf tissue density (LTD), leaf nitrogen concentration (LN), stomatal density (SD), vein density (VD), stomatal guard cell length (SL), palisade tissue thickness (PT), spongy tissue thickness (ST) and palisade-to-spongy tissue ratio (PT/ST) across 9 natural populations. The results showed that Q. variabilis exhibited significant plasticity in functional trait variation, primarily driven by environmental factors, with mean annual precipitation (MAP) and soil total nitrogen (STN) emerging as key ecological drivers promoting the coordinated variation in leaf functional traits. Coordinated relationships were observed between leaf economic traits (LMA, LT, LTD, LN) and hydraulic traits (SD, VD, SL), which varied in response to environmental conditions. Furthermore, leaf anatomical traits (PT, ST, PT/ST) were closely linked to both hydraulic and economic traits. These findings provide valuable insights into the adaptive strategies of Q. variabilis and enhance our understanding of plant responses to environmental change at the intraspecific level.

Atmospheric nitrogen (N) deposition and climate warming threaten plantation soil organic carbon (SOC) stability. Soil respiration (R_s), the primary pathway for SOC decomposition, remains poorly understood in terms of regulatory mechanisms. Biochar may mitigate N deposition impacts. However, the mechanisms by which the interactive effects of N and biochar influence Rs through soil microbial community structure, enzyme activity and C–N–P cycling processes, as well as the temperature sensitivity (Q₁₀) of Rs under these interactions, remain unclear. This study investigated these issues through a five-year controlled experiment simulating N deposition and biochar addition in a Larix kaempferi plantation, integrating changes in soil C-cycle-related properties and their interactions. The results revealed that low N addition (LN: 50 kg N ha⁻¹ a⁻¹) increased R_s by 7%, while high-N addition (HN: 100 kg N ha⁻¹ a⁻¹) reduced it by 32%. Low and high biochar treatments (C₅: 5 t ha⁻¹; C₁₀: 10 t ha⁻¹) increased R_s by 8% and 13%, respectively. N and biochar interactions consistently suppressed R_s, reducing it by 12%−20%. LN, C₅ and C₁₀ enhanced Q₁₀, whereas HN decreased it. Additionally, N and biochar interactions stabilized Q₁₀. N addition directly or indirectly inhibited microbial biomass and aggregate stability by elevating available phosphorus and NO₃^--N content, while biochar’s potential to promote SOC was constrained by its diminishing effects over time. Both factors collectively influenced R_s through a chemical–microbial interaction network. This study elucidates the cascading mechanisms linking soil microbial-physicochemical-R_s under N and biochar additions, providing insights for managing soil C emissions under rising temperatures.

Semi-arid grasslands serve as critical carriers for carbon and nitrogen sequestration in ecologically fragile regions, with plant root functional traits playing a pivotal regulatory role. However, current restoration efforts, overly focused on target species selection strategies, may underestimate root networks’ contribution to soil carbon/nitrogen accumulation. This study examined soil organic carbon (SOC) and total nitrogen (TN) storage, and root traits of target species (Leymus chinensis) and plant community across a chronosequence of grazing-exclusion grasslands in China’s semi-arid Songnen Plain. Results showed that both SOC and TN contents generally increased with grazing-exclusion duration, exhibiting a strong positive linear relationship (R² = 0.83, P < 0.001). SOC storage peaked at 27 years (79.89 t ha⁻¹), while TN storage stabilized after 19 years (9.46 t ha⁻¹). Root traits at target species and community levels exhibited similar temporal trends. Variance partitioning analysis revealed that community root traits had stronger independent effects on SOC/TN storage than target species. The random forest model identified community root carbon content (RCC), root weight (RW), root diameter (RD), and special root length (SRL) as key predictors. Structural equation modelling further indicated grazing exclusion directly and indirectly influenced SOC/TN accumulation. Specifically, reduced community SRL negatively affected RCC and RD, thereby promoting SOC and TN storage, respectively. This study underscores that community root traits, particularly their trade-off relationships, play a more pivotal role than target species in regulating soil functions, thereby establishing a novel trait-based framework for guiding grassland restoration in semi-arid regions.

Although water use strategies of tree species are critical for maintaining tropical rainforest ecosystem function, the water use pattern of dominant tree species in tropical secondary forests remain poorly understood. In this study, with stable isotopes, we analyzed the plant water use sources and intrinsic water use efficiency (WUE_i) of five coexisting dominant tree species in tropical secondary rainforests on Hainan Island during the wet season. The results showed that the shallow soil (0–40 cm) had higher water content than that in deep soil (40–100 cm), the five dominant tree species in tropical secondary forests mainly utilized shallow soil water, with an absorption contribution of 57% compared to deep soil water (43%). Besides, there was no correlation between soil water contribution rate and soil water content in the shallow soil layer, but a significant positive relationship was observed in the deep soil layer (P < 0.01), indicating that deep soil water content has a driving effect on the deep water contribution rate. Meanwhile, the proportional similarity of water uptake between five species exceeded 0.9, suggesting that the water use source of the coexisting dominant species is highly similar. Moreover, the WUE_i of five dominant tree species differed significantly between species (P < 0.05). Both the plant water use source and WUE_i were affected by plant functional traits. Our study demonstrated that there was no soil water partitioning among five dominant tree species in tropical secondary forests, which may intensify water competition amid projected seasonal drought intensification.

The phyllosphere microbiota greatly affects ecosystem carbon and nitrogen cycles, plant productivity and stress tolerance. However, the microbial composition and underlying mechanisms in alpine grasslands of the Qinghai-Tibetan Plateau (QTP) remain unclear. Here, geographic patterns in the abundance, diversity and community composition of phyllosphere microbiota and their functions were explored. We found that both phyllosphere bacterial and fungal community composition displayed a geographical dependence. Climate, especially mean annual precipitation (MAP), played important role in shaping phyllosphere microbial communities over broad geographic scales. The MAP explained 4%–34% of the variation in the phyllosphere microbial community. A distinctive feature of the QTP phyllosphere microbiota was the prevalence of positive correlations in microbial co–occurrence networks, contrasting with patterns observed in other ecosystems. Further analysis revealed that ecosystem multifunctionality was strongly associated with microbial abundance and interspecies interactions, with bacterial communities exerting a disproportionately large influence compared to fungi. These findings provide a solid understanding of patterns and drivers of phyllosphere microbial community and function across alpine grasslands on the QTP, which offer new perspectives for sustainable alpine grassland management.

Bare patch encroachment is linked with a shift in dominant plant species during the degradation of alpine meadows. Here, we investigated the dominant herbaceous species, and the occurrence of shrub invasion and bare patch cover during grassland degradation on 36 hillslopes along a watershed on the Qinghai-Tibetan Plateau. The increase in bare patch cover was treated as a measure of bare patch encroachment and examined in relation to shifts in dominant species. Based on the first two axes of principal coordinate analysis (PcoA1 and PcoA2), there were evident shifts in dominant herbaceous species. The PcoA1 axis represented a shift of dominant herbaceous species from K. pygmaea to Artemisia frigida and Ligularia virgaurea, while the PcoA2 axis represented a shift from K. pygmaea to Aster tataricus. Based on random forest and linear mixed models, both PcoA1 and PcoA2 were important predictors of bare patch encroachment. Furthermore, the structural equation model supported that the number of active pika burrows mediated the positive relationship between PcoA1 and bare patch cover, while the surface soil gravel cover mediated the relationship between PcoA2 and bare patch cover. These findings highlighted the ecological association between the shift of dominant species and bare patch encroachment, advancing previous findings by identifying the toxic species A. frigida, L. virgaurea and A. tataricus as biotic indicators and benefiting the management of the degrading alpine meadow hillslopes.

Aboveground biomass is a key metric for assessing ecosystem structure and function. Worldwide, sedge wetlands are distributed across temperate marsh and montane regions and have critical ecological functions including carbon storage, biodiversity maintenance and climate regulation. However, little is known about aboveground biomass patterns in sedge wetlands at landscape scales. In this study, we combined field data from 125 sedge wetland sites with remote sensing information on solar radiation and climate to evaluate the impact of abiotic (e.g. solar radiation, climate, soil properties and water regime) and biotic (e.g. plant species richness and community type) factors on aboveground biomass. Our results revealed significant heterogeneity in the aboveground biomass of sedge wetlands across different climatic zones in China. Both abiotic and biotic factors exerted influences on aboveground biomass variation in sedge wetlands, although biotic factors dominated patterns of aboveground biomass. Plant species richness promoted aboveground biomass, while the relationship between aboveground biomass and species richness was modulated by community type. Furthermore, mean annual precipitation was identified as the most effective abiotic indicator of aboveground biomass, exhibiting a positive correlation with aboveground biomass. Soil properties directly affected aboveground biomass, and indirectly through species richness and community type. Our study demonstrates the importance of abiotic and biotic drivers in mediating the productivity of sedge wetlands in China and helps predict the response of wetland function to future environmental changes.

Due to global change, the dominance of ectomycorrhizal (ECM) tree species is continually decreasing in temperate forests, which is expected to greatly alter soil carbon and nitrogen dynamics. However, the specific mechanisms through which ECM tree dominance affects soil carbon and nitrogen, particularly via regulating above- and belowground forest properties, remain poorly understood. Here, we investigated the relationships of forest above- (e.g., tree species richness and basal area, leaf nutrient content) and belowground properties (e.g., soil microbial community, enzymatic activity) with soil organic carbon (SOC) and nitrogen along an ECM tree dominance gradient in a temperate forest. We found significant changes in above- (i.e., leaf nutrient content, basal area) and belowground (i.e., fungal community, enzymatic activity) forest properties along the ECM tree dominance gradient. For instance, tree basal area and saprotroph abundance increased with ECM tree dominance, while leaf nitrogen content and enzymes related to soil carbon or nitrogen (β-1,4-glucosidase, cellobiohydrolase, β-N acetylglucosaminidase) decreased. Notably, structural equation modeling suggested that ECM tree dominance negatively affected SOC through regulating aboveground properties. However, ECM tree dominance affected soil nitrogen content and transformation rates by regulating both above- and belowground properties, highlighting different pathways through which soil nitrogen vs. SOC respond to ECM tree dominance change. Therefore, ECM tree dominance can affect soil carbon and nitrogen by distinctively regulating above- and belowground forest properties, and both above- and belowground changes should be considered when predicting how temperate forests will respond to the global-change-induced decline in ECM tree dominance.

Global climate change-induced alterations in precipitation patterns have introduced uncertainty regarding soil carbon sequestration capacity in brackish wetlands. To investigate the effect of seasonal precipitation distribution (SPD) on soil carbon emissions, we conducted a field experiment in a brackish wetland in the Yellow River Delta, maintaining consistent annual precipitation but varying SPD (+73%, +56%, CK, −56%, and −73%). Increased precipitation during the spring was followed by decreased precipitation in the summer and fall (+73% and +56%), whereas decreased spring precipitation was followed by increased summer and fall precipitation (−56% and −73%). Precipitation remained consistent across all treatments during winter. The results revealed significant seasonal and inter-annual sensitivity of soil CO₂ fluxes to SPD, with the spring precipitation enhancement (+56%) treatment exerting a greater influence on emissions than the +73% treatment. In contrast, soil CH₄ fluxes exhibited no statistically significant variations across seasons or in response to precipitation adjustments. Furthermore, hydrological mediation of SPD established inverse water-salt dynamics: increased precipitation in spring mitigated soil salinity, promoting vegetation colonization and growth, while reduced precipitation in summer and autumn alleviated inundation pressure, enhancing vegetation productivity. Increases in soil CO₂ fluxes driven by SPD were primarily attributed to alleviation of salinity stress and vegetation-mediated carbon partitioning, whereas CH₄ fluxes remained statistically constant across precipitation regimes. Therefore, we conclude that SPD predominantly affects soil carbon emissions in the brackish wetland by modifying soil CO₂ fluxes. These findings provide mechanistic insights for refining predictive models of wetland carbon cycling under climate-driven precipitation reconstruction.

The β-diversity, as the variation in community composition across habitats, is crucial for understanding regional community assembly and biodiversity conservation. While biogeographic patterns of both macro- and microorganisms have been well-documented, little is known about studies that simultaneously examine these patterns and their driving mechanisms across continuous spatial scales in both above- and belowground communities. Here, we conducted a field survey along a 1700-kilometer transect across diverse landscapes, including meadow steppe, typical steppe, desert steppe and inland dunes in the semi-arid region (aridity ranging from 0.66 to 0.83) of northern China to investigate patterns and drivers of β-diversity in plant, bacterial and fungal communities at continuous spatial scales. We found that organisms with various dispersal traits exhibited significantly different distance-decay relationships, with plants showing the steepest slope (−0.190), followed by fungi (−0.095) and bacteria (−0.061). Species turnover was the primary component of β-diversity across plant, bacterial and fungal communities at various spatial scales. Furthermore, β-diversity, its turnover components, and β-deviation of plant, bacterial and fungal communities all showed significant and positive relationships with spatial scale. Moreover, environmental distance had a greater impact on β-diversity patterns than geographic distance. Among environmental factors, aridity emerged as the dominant driver significantly influencing the β-diversity of plant and microbial communities, with the strongest effect on the bacterial community. These findings provide essential insights into the mechanisms influencing β-diversity in both plant and soil microbial communities, highlighting the importance of spatial scale and environmental filtering in community assembly.

The home-field advantage (HFA) hypothesis posits that leaf litter decomposes faster at its native sites (‘home’) than in foreign sites (‘away’). While litter quality critically regulates decomposition and HFA, the interplay among litter quality, soil nutrients, and microbial activity in driving HFA remains poorly understood. We examined these dynamics in subtropical forests using Pinus massoniana (low-quality litter) and Schima superba (high-quality litter) in a reciprocal transplant decomposition experiment, including a 1:1 mixed-litter treatment. Our results revealed pronounced HFA effects in both forest stands, but litter quality was negatively correlated with both the decomposition rate and HFA magnitude. Soil nutrients regulated HFA effects, accounting for 56% of the variation in low-quality litter (vs. 25% for high-quality litter). Low-quality litter exhibited greater sensitivity to soil microbial metabolic activity. Soil microbial biomass enhanced HFA in the low-quality litter forest stand but suppressed it in the high-quality forest stand. Enzymatic activity (e.g. β-1,4-glucosidase) directly mediates HFA, particularly in the high-quality litter. These findings underscore litter quality as a pivotal factor governing HFA through its interactions with soil nutrients and microbial metabolism, with implications for predicting biogeochemical cycles in forest ecosystems.

Grazing exclusion through fencing is widely used for vegetation restoration in degraded alpine meadows. However, the dynamic responses of plant communities to grazing exclusion remain poorly understood, especially from an integrated perspective of species diversity, niches, and interspecific associations. In this study, we investigated four proximate alpine meadows on the Tibetan Plateau with different fencing durations (0, 2, 6, and 12 years). We assessed the responses of plant diversity, niche characteristics, and interspecific associations to fencing duration, along with relationships among these dimensions. The results showed a unimodal response of plant diversity to fencing duration, with the Patrick richness index varying in coordination with niche and interspecific association metrics. After 2 years of fencing, the community niche breadth expanded, accompanied by increased niche overlap and Ochiai association index among major species. By 6 years of fencing, the niche breadth shifted toward lower values, and niche overlap of major species decreased significantly, with the proportion of species pairs with high overlap and high association reduced by 21.95% and 25.93%, respectively. After 12 years of fencing, niche overlap rebounded significantly, and the proportion of species pairs with high niche overlap and high association increased by 18.79% and 16.84%, respectively. Our findings support identifying 6 years of fencing as a critical intervention point. At this stage, the community achieves a dynamic balance between competition and coexistence through niche differentiation, maintaining high species diversity. We suggest moderate disturbance should be implemented in alpine meadows thereafter to prevent retrogressive succession.

Density dependence, both conspecific and heterospecific, is widely recognized as a crucial driver of plant species diversity. However, treating multiple heterospecific species as a homogeneous group obviously overlooks the variability in the impacts of different heterospecific neighbors on the survival or growth of focal species. In this study, we developed the Static-Dynamic Coupled Interspecific Association Classification Framework (SDIACF), which categorizes heterospecific neighbors based on their positive/negative interspecific associations and dynamic changes with focal species. We further used generalized linear mixed-effect models to analyze how conspecific and various heterospecific neighbors classified by the above framework influenced the survival and growth rates of the focal species. Our results revealed that heterospecific neighbors, deconstructed using SDIACF, exerted distinct effects on the focal species. Specifically, regardless of their initial interspecific association with the focal species, heterospecific neighbors with more negative associations showed a negative impact on the focal species, while those with more positive associations showed a positive effect. However, among heterospecific neighbors exhibiting identical dynamic interspecific associations, positively associated neighbors were slightly more conducive to the survival of the focal species than negatively associated ones, but slightly detrimental to its growth. In summary, our results demonstrate that heterospecific neighbors are not a homogeneous entity but play important and complex roles in species coexistence. The development of SDIACF not only constitutes a significant supplement to traditional density dependence research but also offers a novel perspective for further exploring species coexistence.