Soil microbial communities play an important role in driving diverse ecosystem functions and ecological processes and are the main driving force for maintaining biogeochemical cycles. To investigate the effects of nitrogen fertilizer addition on soil microbial community characteristics and ecosystem multifunctionality in alfalfa fields, a field experiment was conducted in the semi-arid region of the Loess Plateau. Ecological network analysis revealed a strong cooperative relationship among bacterial community species under the N100 treatment, while a strong competitive relationship was observed among fungal community species under the N50 treatment. Furthermore, compared with the control check, the soil carbon nutrient function, ecosystem multifunctionality and grassland productivity of N150 treatment increased by 45.17%, 34.01%, and 7.92%, while the soil phosphorus function decreased by 13.44%. Additionally, soil pH significantly influences ecosystem multifunctionality, soil carbon nutrient function, and grassland productivity. Soil water content notably affects the soil phosphorus nutrient function, while soil microbial diversity has a significant impact on grassland productivity and soil potassium nutrient function. The above results suggest that alterations in soil nutrient levels influence ecosystem multifunctionality by regulating microbial community diversity, offering new insights into the mechanisms by which nutrients impact soil microbial communities and ecosystem properties.

The Qinghai–Tibet Plateau’s alpine grasslands are ecologically vulnerable. Plateau zokors build mounds that modify soil and vegetation, influencing soil biota. This study examined how different vegetation on zokor mounds affects soil nematodes and ecosystem function. We compared undisturbed grassland (CK), Potentilla anserina (PM) and Leontopodium (LM) mounds, and new bare mounds (NM). Soil nematode communities were analyzed to assess functional indices and metabolic footprints. Compared with CK, PM increased total nematode abundance by 37.74%, r-strategists by 36.54%, and K-strategists by 39.37%. NM increased dominance (λ) by 22.20%, channel ratio (NCR) by 8.89%, and the Wasilewska index (WI) by 1.24 times, but reduced Shannon diversity by 8.49%, trophic diversity (TD) by 22.84%, and species richness (SR) by 29.40%. LM decreased the maturity index (MI) of free-living nematodes by 7.19% and increased the plant parasite index (PPI) by 10.01%. PM exhibited the highest metabolic footprints for bacterivores, fungivores, omnivores/predators, and total nematodes. Soil carbon (EF-C), nitrogen (EF-N), phosphorus (EF-P) cycling functions, and overall ecosystem multifunctionality (EMF) were highest in CK and lowest in LM. Soil moisture had positive effects on EF-N, EF-P, and EMF, whereas pH had a negative effect on EF-C. These findings demonstrate that vegetation-covered zokor mounds influence nutrient cycling and ecosystem multifunctionality through changes in nematode community characteristics, providing new insights into soil biodiversity–function relationships and informing grassland restoration strategies in high-altitude ecosystems.

The Loess Plateau is one of the most vulnerable areas in the world. Numerous studies have been conducted to investigate alfalfa fields with different planting years. Soil microorganisms and nematodes are vital in ecosystem functionality and nutrient cycling. Therefore, comprehending their response to alfalfa fields with varying years of planting is essential for predicting the direction and trajectory of degradation. Alfalfa fields with different planting years (2 years, 9 years, and 18 years) were used as the research object, and farmland was used as the control (CK). High-throughput sequencing and morphological methods determined the community composition of microorganisms and nematodes. Carbon metabolic footprints, correlation networks, and structural equations were used to study soil microorganisms and nematode interactions. Principal component analysis (PCA) results showed that alfalfa fields with different planting years significantly impacted soil microorganisms and nematode community structures. Planting alfalfa significantly increased the nematode channel ratio (NCR) and Wasilewska index (WI), but significantly reduced the soil nematode PPI/MI and dominance (λ). The correlation network results indicated that, for the 2-year and 18-year treatments, the total number of links and positive links are higher than other treatments. Conversely, the 9-year treatment had fewer positive links and more negative links compared to other treatments. Additionally, the keystone species within each network varied based on the treatment years. Structural equation results show that alfalfa planting years directly impact soil fungal community structure and plant-parasitic nematodes’ carbon metabolism omnivorous-predatory nematodes. Furthermore, the carbon metabolism of omnivorous-predatory nematodes directly influences soil organic carbon fixation. Moreover, as the duration of alfalfa planting increases, the metabolic footprint of plant-parasitic nematodes decreases while that of omnivorous-predatory nematodes rises. Among treatments varying in alfalfa planting durations, the 9-year treatment exhibited the most incredible energy conversion and utilization efficiency within the soil food web, demonstrating the most stable structure. This study reveals optimal alfalfa planting duration for soil ecosystem stability in the Loess Plateau. Future research should explore sustainable crop rotations and alfalfa–soil–climate interactions for improved agricultural management.

To reveal how the altitude gradient regulates the effects of rhizosphere microbial dynamics on ecosystem multifunctionality in Hylodesmum podocarpum, a field experiment was conducted across four elevation transects (a.s. 896–1805 m) in the Qinling Mountains. The results showed that rhizosphere soil exhibited peak microbial diversity richness at 1805 m (HB4), with bacterial communities showing a strong interspecific cooperative relationship, while the fungal communities showed a competitive relationship. In addition, this study found the assembly process to be different. Bacterial assemblages changed from random processes (HB1, HB2, HB3) to deterministic processes (HB4), whereas fungal assemblages remained stochastic processes across all elevations. Our results also revealed that synergistic interactions among soil carbon, phosphorus, and nitrogen nutrient functions collectively enhanced nutrient-centered soil multifunctionality. Notably, carbon and phosphorus nutrient functions emerged as the primary drivers of soil multifunctionality. Further mechanistic analysis revealed that while soil pH exerted significant control over both carbon and nitrogen nutrient functions, microbial mediation exhibited functional specialization: bacterial communities predominantly regulated carbon cycling, whereas fungal communities played a more comprehensive role in modulating carbon, nitrogen, and phosphorus dynamics along with overall ecosystem multifunctionality. This finding suggested that altitude gradients indirectly affect the characteristics of the microbial community by regulating soil nutrient status, thereby driving changes in ecosystem multifunctionality. This finding provides new insights into how nutrients regulate ecosystem functions through microbial pathways.

Vegetation restoration is an effective strategy to improve the ecosystem function of the Loess Plateau. Soil microbiomes play a critical role in maintaining soil multifunctionality (SMF). However, the role of aggregate-scale microbial communities and interactions in regulating SMF during vegetation restoration remains poorly understood. Here, we selected six types of vegetation restoration measures in the Loess Plateau, including natural grassland (NL), Medicago sativa (MS), Hippophae rhamnoides (HR), Caragana korshinskii (CK), Armeniaca vulgaris (AV), and Populus alba (PA), and used abandoned land (AL) as a control to identify key microbial mechanisms driving SMF at the aggregate scale. The results show that vegetation restoration increased bacterial diversity, fungal network complexity, and SMF, especially in AV. In contrast, fungal diversity and bacterial network complexity exhibited asynchronous dynamics across different-sized aggregates. Soil microbial diversity peaked at micro-aggregates (0.053–0.25 mm), while fungal network complexity increased with decreasing aggregate size. The structural equation model confirmed that fungal community composition in large macro-aggregates (>2 mm) and fungal network complexity in <2 mm aggregates were the key drivers of SMF. Our results emphasize the divergent mechanisms by which microbial properties influence SMF across aggregate sizes, highlighting the importance of fungal communities in maintaining soil ecosystem functions.

Soil microbial communities are fundamental to soil health and ecosystem functioning in agricultural landscapes. This study assessed how soil nutrient variation influences microbial community structure and ecosystem multifunctionality in tea gardens across three counties in Longnan, China. Key findings revealed that Kangxian tea garden soils exhibited 18–25% higher bacterial and fungal richness and diversity indices than Wenxian, which had the lowest values among the three counties. Co-occurrence network analysis indicated a 32% higher proportion of positive (cooperative) interactions among microbial taxa in Wenxian soils. Null model analysis showed that bacterial community assembly was primarily driven by deterministic heterogeneous selection, whereas fungal assembly was governed by stochastic ecological drift. Functionally, Wenxian soils demonstrated 22% higher carbon sequestration, 19% higher nutrient storage, and 17% higher nutrient supply than the other counties (p < 0.05), while Kangxian soils had 21% greater nutrient cycling and overall ecosystem multifunctionality. Soil C/P and N/P ratios significantly influenced carbon sequestration, nutrient storage, and multifunctionality (explaining up to 48% of the variance), while soil pH was a key driver of carbon sequestration, nutrient supply, and cycling. Both bacterial and fungal community structures significantly impacted nutrient storage and multifunctionality. Regional differences in soil nutrients, shaped by tea garden management, directly influence microbial community traits and ecosystem multifunctionality. Targeted nutrient management and enhanced microbial diversity are key to improving soil multifunctionality and sustainability in tea agroecosystems.