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.

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.

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.

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