Biodiversity-ecosystem function research has increasingly recognized the importance of belowground communities, yet how multidimensional traits of soil nematodes shape ecosystem functions across environmental contexts remains poorly understood. Using data from two large-scale transects on the Mongolian Plateau, we develop an integrative framework to assess how taxonomic diversity, ecological indices, and metabolic traits of nematode community drive ecosystem multifunctionality (EMF) across grassland types spanning a resource gradient. We found that nematode α- and γ-diversity, ecological indices, and metabolic traits increased from desert to meadow steppe, while β-diversity declined. Overall, aboveground, and belowground EMF responded similarly, all peaking in meadow steppe. Aboveground EMF was governed primarily by precipitation, whereas belowground and overall EMF integrated both abiotic drivers and direct positive effects of nematode ecological indices and metabolic traits. Critically, regulatory mechanisms shifted along the gradient: abiotic factors dominated in resource-poor systems (desert, desert steppe), while plant diversity and nematode traits became significant direct drivers and direct abiotic effects weakened in resource-rich systems (typical steppe, meadow steppe). Aboveground EMF remained consistently climate-dominated. Our findings reveal fundamental context dependence in biodiversity–ecosystem functioning relationships, with important implications for predicting grassland responses to global change and informing grassland management.
Woodlice, as one of the key groups, contribute to the decomposition of litter in ecosystems. However, the resource use by woodlice, which likely depends on the body size and developmental stage, remains poorly understood. Understanding ontogenetic shifts in the composition of stable isotopes δ13C and δ15N is essential for assessing the position of woodlice in soil food webs. We applied the stable isotope analysis of carbon and nitrogen to four ontogenetic stages of two synanthropic cosmopolitan woodlice species, Cylisticus convexus and Oniscus asellus, along with their potential food resources in a city park in Moscow, Russia. We compared mancas, juveniles, young adults, and adults. In C. convexus, the δ13C values remained constant, while juveniles, young adults and adults were enriched in 15N compared to mancas. In O. asellus, δ13C values remained constant except for the last age (adults), when they were enriched in 13C by about 1.5‰, compared to other ages. Young adults of O. asellus were depleted in 15N compared to other ages. Bayesian mixing models (MixSIAR) indicated leaf litter as the primary dietary resource for both species, with species-specific differences in the contribution of fungi and moss. These results suggest ontogenetic shifts in resource use within woodlice populations. We demonstrate the need to consider the age of woodlice when interpreting isotopic data and assessing their trophic roles in soil ecosystems.
Soil priming effect (PE) and microbial carbon use efficiency (CUE) are key drivers of soil carbon (C) cycling, yet their regulatory mechanisms remain unclear in coastal saline soils with high salinity and limited organic C. In this study, 13C-labeled maize straw was used as a standardized exogenous organic material in a 180-day incubation experiment to trace microbial C transformation processes in coastal saline soils of the Bohai Rim, China. The effects of a salinity gradient (low, medium, high) on PE and microbial CUE were evaluated, and the influence of increased C availability via field straw return on these parameters was also examined in low- and medium-salinity soils. The study showed that soil salinity reduced microbial biomass C (MBC) and the activities of C-, nitrogen (N)-, and phosphorus (P)-transforming enzymes, resulting in a negative linear relationship between microbial CUE and salinity. Straw return further decreased MBC and extracellular enzyme activities in low-salinity soils, leading to a 22.25% decline in CUE, whereas no significant changes in MBC or CUE were observed in medium-salinity soils. The PE exhibited a non-linear, threshold-like response to salinity: under low-salinity conditions, PE was primarily controlled by SOC availability, whereas under high-salinity conditions, the physical protection of SOC was compromised, promoting C mineralization. In the short term (20 days), straw return significantly suppressed PE in low-salinity (by 37.24%) and medium-salinity (by 65.58%) soils, likely due to enhanced SOC physical protection (as indicated by a significant decrease in the labile organic C (LOC):SOC ratio) and total N (TN) accumulation following straw return. Overall, this study demonstrates that while salinity determines microbial C metabolism and PE, the effects of straw return are salinity-dependent, suggesting that organic matter management in coastal saline soils should consider both salinity conditions and straw application strategies to optimize C sequestration.
Recycling spent mushroom substrate (SMS) to agricultural fields is a widely adopted strategy for organic waste valorization. However, the decomposition characteristics, nutrient release patterns, and microbial succession of SMS under different return rates and nitrogen fertilization regimes remain unclear; we used high-throughput sequencing, enzyme activity assays, and physicochemical analysis to investigate them. In this field experiment, three replicated plots were established per treatment, and destructive sampling was performed at nine time points over 110 days. Overall, the SMS decomposition rate decreased significantly from 5.39 ± 1.42 g d−1 at the early stage to 1.85 ± 0.27 g d−1 at the late stage (P < 0.001, Welch's t-test). Nitrogen fertilization significantly suppressed enzyme activities and decomposition rate, and this effect did not differ significantly among stages (stage × nitrogen, P > 0.05). SMS application rate also significantly affected decomposition, with the lower rate showing a higher decomposition rate overall. The microbial co-occurrence network reached its highest complexity and stability (bacterial AUC = 54.267, fungal AUC = 9.663) at the middle stage, along with the largest niche breadth. Structural equation modeling revealed that the decomposition rate was directly influenced by microbial diversity (Std. β = 0.444, P < 0.001) and residue properties (Std. β = 0.515, P < 0.001), whereas community structure had only indirect effects. This study provides practical guidance for the efficient soil application of SMS under nitrogen fertilization, contributing to the sustainable utilization of agricultural organic wastes.
Excess nitrogen (N) is fundamentally reshaping soil microbial communities and the biogeochemical networks that sustain ecosystem functioning. Beyond changes in microbial diversity, increasing evidence suggests that excessive N inputs reorganize microbial interaction networks, with cascading effects on nutrient cycling, plant-microbe relationships, and climate feedbacks. Here, we synthesize emerging insights into how N enrichment alters soil microbial network architecture and the ecological mechanisms underlying these transformations. We propose that microbial network responses to N enrichment are context dependent, governed by nutrient availability, microbial life-history strategies, soil properties, and ecosystem characteristics. Nitrogen-driven shifts in microbial traits, keystone taxa, and interspecific interactions can modify carbon and nitrogen turnover, influence greenhouse gas dynamics, and alter plant health outcomes. However, co-occurrence networks mainly capture statistical associations and require integration with functional, experimental, and process-based approaches to establish causality. Bridging microbial network ecology with biogeochemical theory and sustainable N management will advance our ability to predict ecosystem responses to ongoing global nitrogen perturbations.
