Leaf and root litter profoundly impact soil carbon sequestration and nutrient cycling in terrestrial ecosystems. Recent evidence indicates that within single-species contexts resource traits are coordinated between leaves and roots driving parallel decomposition dynamics of leaf and root litters, yet it remains unclear whether this coordination also underlies parallel mixing effects in leaf and root litter mixture decomposition. In a 501-day field experiment in a temperate steppe, we incubated leaf and fine root litters from six species alone and in all pairwise mixtures. We assessed the relationship between leaf and fine root litter decomposition responses to litter mixing, and examined how trait dissimilarity between component species and decomposition responses of four carbon fractions (soluble compounds, hemicellulose, cellulose and lignin) shape this relationship. We found litter trait dissimilarities drove contrasting fraction-level responses to litter mixing. Most leaf and fine root litter mixtures exhibited non-additive effects in soluble-compound and cellulose decomposition, with soluble compounds contributing most to the overall non-additive effects of mixed leaf and fine root litters. Coordinated dissimilarity in leaf and root traits led to parallel decomposition responses of leaf and root soluble compounds to litter mixing, but to negative correlations for hemicellulose and cellulose and no correlation for lignin. These divergent fraction-level relationships blurred overall coordination of decomposition response between leaf and fine root litters to litter mixing, causing uncoordinated bulk-litter mixing effects. Our results demonstrate that resolving fraction-level processes is critical for understanding mixed-litter decomposition and for predicting ecosystem carbon and nutrient fluxes under changing plant communities.

Nitrogen (N) availability critically limits plant productivity in nutrient-depleted coral island ecosystems, necessitating substantial inputs of exogenous N fertilizer. However, excessive or unbalanced fertilization poses risks to environmental sustainability. In this study, we assessed how three N fertilizer forms, ammonium (NH₄⁺-N), nitrate (NO₃⁻-N) and amide nitrogen (NH₂-N), affect soil properties and plant performance in coral sand environments. A 15N-labeled greenhouse experiment was conducted using two island-adapted species, Ficus microcarpa and Terminalia catappa. Results showed that NO₃⁻-N markedly enhanced nitrogen retention, microbial biomass nitrogen and overall plant growth, while NH₄⁺-N promoted microbial biomass carbon. Ficus microcarpa and T. catappa both exhibited superior growth under NO₃⁻-N, although T. catappa achieved higher leaf nutrient concentrations with NH₂-N, reflecting differences in nutrient uptake preferences. Isotopic tracing revealed greater nitrogen retention in soils than in plant tissues, with NO₃⁻-N fertilization yielding the highest nitrogen recovery efficiency. These findings highlight the importance of nitrogen form in shaping soil–plant interactions in sandy, alkaline soils and offer mechanistic insights for designing targeted, sustainable fertilization strategies for coral island ecosystems.

Ecosystem temporal stability (TS) determines its ability to maintain structure, function and services under external disturbances, playing a critical role in the global carbon cycle and climate regulation. However, the capability of numerical models to simulate the TS of ecosystem carbon uptake remains insufficiently assessed. This study evaluated the performance of nine terrestrial ecosystem models in simulating gross primary productivity (GPP) and its TS and employed Random Forest (RF) models with Shapley Additive Explanations (SHAP) to identify key factors contributing to model biases. Site-scale analysis based on flux tower observations indicated that most models underestimated GPP while overestimating its TS, with the most pronounced biases occurring at the interannual scale. These discrepancies primarily stemmed from errors in simulating vegetation phenology, specifically the carbon uptake period and physiological traits, particularly peak GPP within a year. At the global scale, regions with higher carbon uptake tended to exhibit greater TS, yet significant discrepancies existed among models. Notably, RF and SHAP analyses indicated that leaf area index was more important than climate and geographical factors in explaining model divergence for simulating GPP and its TS. The study revealed systematic biases in the current models’ representation of TS, highlighting the potential vulnerability of ecosystems. These uncertainties among models may lead to an overestimation of ecosystem resilience, introducing uncertainties in global carbon budget estimates and potentially misguiding scientific assessments and policy decisions regarding future climate change responses. Therefore, improving carbon cycle simulation mechanisms is essential for enhancing model predictive capabilities.

The expansion of toxic weeds represents a key symptom of grassland degradation and exerts profound effects on ecosystem structure and function. These species often facilitate their establishment by forming a fertile island effect, yet how this process varies across large geographic scales and its underlying mechanisms remain poorly understood. Here we conducted large-scale field sampling at 20 grassland sites spanning over 3000 km to investigate the soil fertile island effect of a dominant toxic weed (Stellera chamaejasme L.) in China. We found that the presence of S. chamaejasme coincided with increased contents of soil organic carbon, dissolved organic carbon, total nitrogen, nitrate and ammonium, with the most pronounced fertile island effects observed for soil organic carbon, dissolved organic carbon and ammonium. Furthermore, these fertile island effects declined with increasing aridity, either directly or indirectly through microbial processes. These findings suggest that S. chamaejasme is more effective at forming the fertile island effect and promoting its expansion in wetter regions, highlighting the importance of regionally adapted strategies for toxic weed control.

Submerged macrophytes play a vital role in the carbon cycling of lake ecosystems. However, the extent to which contrasting macrophyte growth forms—bottom-dwelling versus canopy-forming—control annual CO₂ and CH₄ emissions is unresolved, limiting evidence-based guidance for lake restoration aimed at carbon mitigation. We conducted a fully replicated, year-long outdoor mesocosm experiment under natural temperature and light regimes to quantify greenhouse gas fluxes from monospecific stands of four widespread macrophytes: bottom-dwelling Vallisneria denseserrulata and canopy-forming Ceratophyllum demersum, Myriophyllum spicatum and Hydrilla verticillata. Monthly diffusive flux measurements were integrated with high-resolution data on water chemistry, macrophyte biomass, zooplankton, phytoplankton and the functional genes mcrA and pmoA for methanogenic and methanotrophic communities. Canopy-forming macrophytes reduced annual CO₂ fluxes by 5–13 mol m⁻² yr⁻¹ relative to bottom-dwelling treatments, with Hydrilla and Myriophyllum systems functioning as net carbon sinks (negative CO₂-equivalent balance), whereas Vallisneria and Ceratophyllum remained sources. Canopy-forming macrophytes exhibited higher biomass than bottom-dwelling forms, enabling greater nutrient uptake and correspondingly higher CO₂ fixation via photosynthesis. CH₄ release was strongly modulated by plant biomass and associated redox conditions. These results demonstrate that canopy-forming macrophytes offer superior potential for CO₂ mitigation and CO₂-equivalent balance, providing essential tradeoff information for managers selecting plant assemblages for climate-smart lake restoration

Elevated ground-level ozone (O₃) is known to inhibit plant growth and development, but its interactive effects with other climate factors, such as elevated carbon dioxide, warming, drought, and nitrogen deposition, remain poorly understood. Here, a comprehensive meta-analysis was conducted to investigate the main and interactive effects of O₃ and multiple climate factors on plant photosynthetic rate, stomatal conductance, biomass production, and allocation. Our findings revealed a consistent pattern of O₃-induced overall reduction in plant photosynthesis, stomatal conductance, and biomass production across different CO₂, temperature, drought, and nitrogen deposition conditions. Elevated O₃ exposure caused significant declines in biomass production, with crops experiencing the largest reduction, followed by trees and grasses. The greater biomass loss in crops and trees might be due to their physiological traits, longer exposure durations, or agronomic management practices. Elevated CO₂ alleviated the negative effects of O₃ on plants, but it was reflected in the photosynthetic rate. Although the O₃-induced decrease in stomatal conductance and root biomass was reduced by increasing temperatures, warming had a limited effect on improving plant resistance to O₃. Interestingly, O₃ damage was reduced by drought through decreased stomatal conductance, whereas nitrogen addition did not affect the harm caused by O₃. Our findings provide insights into plant gas exchange, biomass, and allocation responses to the interaction of O₃ and climate factors, improving the understanding of plant adaptive mechanisms in the context of global change.

Despite increasing evidence regarding the positive effect of structural diversity on forest functioning, the underlying biotic and abiotic mechanisms remain poorly understood. Critically, how structural diversity in different forest strata affects productivity components, such as growth of surviving trees, recruitment of new individuals and biomass net change incorporating mortality, is largely unknown. Here, we used lidar and repeated census data to examine the relationship between structural diversity and forest productivity in a 9-ha temperate forest plot in Northeast China. We quantified the contributions of species diversity, functional diversity, functional composition, structural diversity, and environmental factors to productivity using hierarchical partitioning and structural equation modeling. We found that structural diversity was strongly associated with forest productivity, accounting for 65% of the influence of all variables on net productivity change. We found that structural diversity mediated the effects of other biodiversity attributes (species diversity and functional diversity) and environmental factors on productivity. However, overstorey and understorey structural diversity exerted contrasting effects on productivity. Overstorey structural diversity elevates productivity by enhancing canopy space filling and light capture. Conversely, a structurally diverse understorey signaled intense competition for water and soil nutrients, thereby suppressing the growth of large trees. Our study suggests that distinct mechanisms of overstorey and understorey structural diversity on productivity exist, and neglecting this contrast may partly account for the inconsistent observations in structural diversity-productivity relationships. These findings underscore the critical role of structural diversity in shaping forest productivity, providing essential insight for advancing biodiversity–ecosystem functioning (BEF) relationships.

Alien plant invasions threaten native biodiversity, disrupt ecosystem functions and can cause large economic damage. Phenotypic plasticity is considered a key mechanism facilitating plant invasions. Plastic responses can occur not only within a generation but also be transmitted to subsequent generations. However, little is known about how combined plasticity within and between generations affects the growth performance of clonal invaders and their native congeners under drought conditions and whether clonal invaders benefit more from such plasticity. The parental generation of the clonal invader Wedelia trilobata and its native congener Wedelia chinensis were exposed to drought or control conditions. After 10 weeks, rooted offspring ramets from the parental generation were obtained and subsequently exposed to either drought or control conditions. Parental drought significantly enhanced offspring drought resistance in both species. However, the expression of combined plasticity in morphological traits differed significantly between the clonal invader and its native congener. The clonal invader exhibited greater plasticity in specific leaf area and root surface area, while the native congener showed stronger plasticity in root to shoot ratio. Furthermore, combined plasticity significantly increased the total and shoot biomass in the clonal invader’s offspring, a pattern not observed in the native congener. These results indicate that when offspring environments are predictable, combined plasticity can improve offspring drought adaptation in both species, but the clonal invader benefits more. Given the projected increase in drought frequency under climate change, combined plasticity may enhance the competitive advantage of invasive plants, facilitating their establishment and spread in introduced ranges.

Human disturbances can drive the expansion of aggressive native plant species, which can significantly impact ecological communities. Investigating the effects of these species on ecological networks is crucial for biodiversity conservation and management. While previous research has shown that aggressive native plant can negatively affect aboveground pollination networks, their impacts on belowground ecological networks remain unexplored. To address this gap, we conduct field experiments to investigate the ecological impacts of an aggressive native plant, Euphorbia jolkinii Boissier (hereafter Euphorbia), on plant and arbuscular mycorrhizal fungi (AMF) communities, plant–AMF interactions, and mycorrhizal network structures in ten overgrazed subalpine meadows. Our findings indicate that Euphorbia exhibits a high level of generalization in its interactions with AMF. While Euphorbia did not significantly reduce the species richness of neighboring plants or AMF, it notably altered species composition and reduced plant biomass. Furthermore, Euphorbia also affected the interactions among species by altering plant composition and rewiring interactions. These changes led to plant–AMF networks influenced by Euphorbia exhibiting reduced connectance and nestedness but increased modularity. These discoveries underscore the considerable negative impacts of aggressive native plant species on belowground mycorrhizal networks and plant biomass. Our results highlight the necessity to develop effective management and restoration strategies for areas impacted by the expansion of aggressive native species.

Understanding vegetation sensitivity to water deficit is essential for assessing ecosystem vulnerability and adaptive capacity. Based on flux and meteorological data from 77 global sites, we developed a new approach that combines percentile and standard deviation methods to characterize precipitation (PPT) and soil water content (SWC) deficit conditions. Simultaneously, we applied the SWH model to simulate evapotranspiration (ET) processes, separating transpiration (T) from evaporation (E). Spatially explicit analysis revealed significant variations in vegetation sensitivity to PPT and SWC deficits (S_PPT and S_SWC) across ecosystem types, generally intensifying with increasing deficit severity. Notably, nearly half of the sites exhibited contrasting responses, with positive S_SWC but negative S_PPT. This divergence was particularly pronounced in forest ecosystems, likely due to precipitation legacy effects. Moreover, the study revealed the unexpected increase in gross primary productivity (GPP) under SWC deficit conditions at certain sites, which was mechanistically linked to increased T, T/ET, and water use efficiency. We proposed that vegetation exhibits growth inertia, whereby plants that thrive under favorable prior conditions can sustain higher soil water utilization rates and GPP, which in turn leads to soil moisture depletion. Specifically, vegetation actively regulates water use to maintain productivity through transpiration-mediated adjustments, challenging conventional views of passive drought responses. To sum up, these results collectively highlighted that SWC surpasses PPT in determining vegetation sensitivity to water deficit, and that comprehensive vegetation drought sensitivity assessments must explicitly consider the differential impacts of E and T on SWC dynamics.

Climate change intensifies seasonal droughts in alpine meadows on the Qinghai-Tibet Plateau, impacting the adaptability of key plant functional groups. However, how plant functional groups with different flowering phenologies adjust their reproductive allocation through trait-based strategies remains poorly understood. This study examined the effects of spring, summer, and whole growing season drought on reproductive strategies of early-spring flowering (ESF) and mid-summer flowering (MSF) plant functional groups. Results revealed that spring drought significantly reduced the reproductive efficiency of MSF plants, whereas summer drought resulted in higher reproductive efficiency compared to spring drought. ESF plants exhibited greater resilience than MSF plants across all seasonal drought treatments, highlighting the advantage of their drought-avoidance strategy. Under whole growing season drought, ESF plants adopted conservative resource-use strategies, including decreased specific leaf area (SLA) and increased leaf carbon to nitrogen ratio (C/N), carbon to phosphorus ratio (C/P), and leaf dry matter content (LDMC). In contrast, MSF plants experienced phosphorus (P) limitation and height reductions. Notably, whole growing season drought induced interannual cumulative effects in MSF plants, such as increased LDMC and decreased SLA, indicating higher morphological plasticity. Furthermore, ESF plants enhanced flower allocation through both increased P availability and C/N (nutrient-sensitive strategy). For MSF plants, flower allocation was directly regulated by leaf nitrogen content (LNC), indirectly enhanced through resource reallocation from decreased plant height (morphology-integrated strategy). This study elucidates the covariation patterns between functional trait and reproductive allocation in ESF and MSF plants under seasonal drought, providing a mechanistic framework for predicting alpine ecosystems responses to future droughts.

The invasion of Spartina alterniflora poses a significant threat to coastal wetlands in China. The large biomass and organic substrates introduced by this species are likely to alter soil microbial communities and drive methane (CH₄) and other greenhouse gas emissions; however, the underlying mechanisms remain poorly understood. To address this, we conducted a one-year in situ monitoring of CH₄ emission rates, soil properties, dissolved organic matter (DOM) fractions, and CH₄-cycling microbial communities in invaded wetlands and adjacent native mangroves. Our results showed that S. alterniflora invasion increased soil CH₄ emissions by 8.7-fold relative to mangrove soils. Redundancy analysis and structural equation modeling revealed that this increase was closely linked to invasion-induced shifts in soil conditions, including elevated water content and pH, enrichment of labile DOM fractions (lipids and protein/aliphatic compounds), and decreases in sulfate, soil organic carbon, and total nitrogen. These changes reduced DOM molecular stability and collectively facilitated CH₄ production. Moreover, quantitative PCR showed an increase in the absolute abundance of methanogens and a decrease in both the abundance and diversity of methanotrophs in invaded soils. Amplicon sequencing further indicated a higher relative abundance of Methanococcoides and a reduction in type II methanotrophs, weakening methane oxidation capacity. Overall, S. alterniflora invasion enhances wetland CH₄ emissions by altering soil physicochemical properties, providing more labile substrates, and restructuring CH₄-related microbial communities, thereby weakening the carbon-sink function of coastal wetlands. Integrated management approaches are needed to mitigate invasion-driven methane production while sustaining wetland ecosystem resilience.

Nitrogen deposition substantially alters nutrient absorption by plant root systems, which has far-reaching consequences for leaf growth and development. However, its effects on plant phenology and climatic sensitivity remain unclear. This study investigated the effects of nitrogen deposition on vegetation phenology and its sensitivity to moisture and temperature from 1982 to 2022 by combining data from field experiments, remote-sensing observations, and land surface models. The results revealed that the start of the growing season (SOS) has become more sensitive to vapor pressure deficit (VPD), whereas its sensitivity to temperature and soil moisture (SM) has decreased in recent decades. Conversely, there was no notable trend in climatic sensitivity at the end of the growing season (EOS). The model results show that SOS’s sensitivity to VPD (S_VPD) and temperature (S_Tem) increased with higher nitrogen deposition levels (S_VPD, a = 1.07 d unit⁻¹, P < 0.01; S_Tem, a = 0.10 d unit⁻¹, P < 0.01). The sensitivity of EOS to soil moisture (S_SM) decreased significantly with increasing nitrogen deposition (a = −1.82 d unit⁻¹, P < 0.05), whereas S_VPD decreased (a = −0.38 d unit⁻¹, P < 0.01). Attribution analysis indicated that nitrogen deposition was the primary driver of changes in the climatic sensitivity of SOS, whereas atmospheric CO₂ predominantly influenced changes in the S_SM of EOS. These results emphasize the critical role of nitrogen deposition in determining the climatic sensitivity of vegetation phenology and provide a novel perspective for understanding and predicting vegetation phenology dynamics under ongoing global change.

Although the crucial role of plant-soil feedback (PSF) associated with species composition in determining diversity‐productivity relationships has been increasingly recognized, its legacy effects on subsequent diversity‐productivity relationships remain unclear. We conducted a classic PSF experiment to assess how conditioning diversity and species composition shape subsequent diversity‐productivity relationships. Plant communities at four diversity levels (1, 2, 4 and 8 species) were grown in soils previously conditioned at matching diversity levels and one of five species compositions. Additionally, to test whether soil microbial diversity mediates composition effects, the same communities were grown under low, moderate and high soil biodiversity generated via inoculum dilution. Productivity was higher on legume-conditioned soils than on non-legume soils. Legumes also steepened the diversity‐productivity relationship, with the strongest responses following monoculture conditioning. In addition to plant diversity, species composition also shaped soil legacy effects, especially for specific plant functional groups such as legumes. Under the same plant diversity, the extent of soil legacy effects on succeeding plants depended on species composition, particularly under low diversity, and likely promoted subsequent community growth by enhancing nutrient availability and microbial diversity. Our findings highlight that manipulating species composition, particularly the inclusion of legumes, can harness soil legacy effects to enhance ecosystem productivity in ecological agriculture.

Water use efficiency and hydraulic conductivity are critical determinants of plant growth and adaptive ability. In principle, high hydraulic conductivity could result in low water use efficiency because of the selection between resource acquisition and resource conservation in species. However, there is insufficient evidence on whether a trade-off exists between these two plant hydraulic traits across species. Here, we quantified eight leaf and branch functional traits associated with water use efficiency and hydraulic conductivity across 52 dominant woody species from three forests (i.e. dry forest, DF; semi-wet forest, SWF; wet forest, WF) along a precipitation gradient in China. We found that plant water use efficiency and hydraulic conductivity were significantly and negatively correlated. Principal component analysis revealed that DF, SWF, and WF species were significantly isolated along axis 1. In contrast to species distributed in WF and SWF, DF species had the lowest hydraulic conductivity, stomatal conductance, and leaf/sapwood area ratio but showed the highest intrinsic water-use efficiency, leaf carbon isotope ratio, and wood density. Stomatal conductance to water explained the differences in plant water use efficiency among different sites, whereas leaf maximum carbon assimilation rate did not. Our results suggest a trade-off between hydraulic conductivity and water use efficiency, which influences the vegetation features in different sites.

Anthropogenic nitrogen enrichment significantly alters plant community structure and productivity, often undermining long-term stability. However, the role of initial community structure, particularly species evenness, in mediating these stability responses remains inadequately understood. In this study, we conducted an 8-year nitrogen-addition experiment across four alpine grasslands on the Tibetan Plateau, which represent a natural gradient in initial evenness. Our results indicated that initial species evenness was crucial in mediating community stability under nitrogen enrichment. In low-evenness communities, stability exhibited a linear decline with increasing nitrogen, primarily driven by the instability of dominant species, specifically Carex parvula O. Yano in alpine meadows and Stipa purpurea Griseb. in alpine desert steppes. At lower nitrogen levels, dominant species biomass increased; however, as nitrogen levels rose, biomass variability increased, resulting in diminished overall stability. Conversely, high-evenness communities displayed nonlinear stability responses, buffered by species asynchrony. In the alpine meadow steppe, stability initially increased at low nitrogen levels but subsequently declined at higher nitrogen due to reductions in species evenness and functional redundancy. In the alpine steppe, stability first decreased at low nitrogen due to community imbalance, but compensatory dynamics among nitrogen-tolerant species, such as S. purpurea, restored stability at elevated nitrogen levels. These findings emphasize the diverse responses of alpine grasslands to nitrogen enrichment and underscore the significance of initial species evenness for ecosystem resilience. This study offers critical insights for forecasting ecosystem responses and formulating targeted management strategies in the context of global change.

Increasing tree species diversity is an effective practice for forest restoration. It enhances multitrophic diversity and multifunctionality. Soil nematodes play a vital role in enhancing soil health, yet it has not been fully addressed about how tree species diversity affects the multitrophic diversity and interspecific interactions of soil nematodes. We investigated soil nematode communities in a planted forest ecosystem converted from agricultural lands. Soil nematodes were sampled across four tree species richness levels, and classified into four trophic groups (i.e., herbivores, bacterivores, fungivores and predators-omnivores) based on feeding guilds. We analyzed the effects of tree species richness, tree productivity, soil properties and trophic interactions on soil nematode communities. Results showed that total nematode diversity was not affected by tree species richness. The Shannon index of predators-omnivores decreased with tree species richness, while abundance and genus richness of herbivores declined with tree productivity. Structural equation models revealed that soil pH reduced the abundance and genus richness of herbivores and bacterivores through abiotic stress. Conversely, predators-omnivores increased the abundance and genus richness of herbivores and bacterivores via top-down trophic regulation. Notably, tree species richness intensified the complexity of nematode co-occurrence networks. These findings demonstrate that tree species richness, productivity, soil pH and trophic interactions collectively shape soil nematode communities, and that network complexity rather than taxonomic diversity is strongly affected by the plant-soil biota interactions. Our study provides an empirical basis for designing forest restoration schemes that prioritize belowground ecosystem functions.

Ecosystem stability is a fundamental attribute that underpins the delivery of essential ecosystem services. However, most research has primarily focused on the temporal stability of biomass, overlooking the multidimensional nature of stability that cannot be captured by a single metric. In this study, we investigated the effects of nitrogen (N) and phosphorus (P) additions on the stability of plant and microbial communities in alpine meadows of the Qinghai-Tibet Plateau. Our results demonstrated that N and P additions significantly increased plant community biomass but reduced the diversity of plants, prokaryotes, and fungi. Although N and P additions did not significantly reduce biomass stability, a decreasing trend was observed. More importantly, compositional stability was significantly reduced by nutrient additions, with differing underlying mechanisms. Nitrogen addition primarily reduced community compositional stability by decreasing prokaryotic diversity, affecting plant diversity and the stability of subdominant species. In contrast, P addition mainly reduced the compositional stability of dominant species, thereby decreasing overall community stability. Furthermore, N addition significantly decreased the network stability of both prokaryotic and fungal communities. Importantly, microbial diversity and network properties were significantly correlated with plant community stability, highlighting the interconnectedness of above- and belowground communities. Our findings emphasize the need for future research to adopt a multidimensional approach to ecosystem stability, integrating both compositional and functional aspects of plant communities, and incorporating microbial diversity and network characteristics.