Research Highlights: Soil enzymes have a significant impact on the production of glomalin-related soil protein (GRSP), directly and indirectly affecting the nutrient metabolism balance, but there is little available information on ecological stoichiometry in soil aggregates. Background and Objectives: Vegetation restoration changes community structure and species composition in ecosystems, thus changing the physicochemical properties of soil. Soil aggregate is the most basic physical structure of the soil. Therefore, in order to understand dynamic changes in soil aggregate nutrients as vegetation restoration progresses, we set out to investigate the nutrient distribution and utilization in aggregates, and how enzymes respond to the nutrient changes in achieving a nutritional balance along successive stages of vegetation restoration. Materials and Methods: We collected and analyzed soil from plots representing six different stages of a vegetation restoration chronosequence (0, 30, 60, 100, 130, and 160 years) after farmland abandonment on the Loess Plateau, China. We investigated soil nutrient stoichiometry, GRSP, and enzyme stoichiometry in the different successional stages. Results: The results revealed that soil organic carbon, total nitrogen, enzyme activity, and GRSP increased with vegetation recovery age, but not total phosphorus, and not all enzymes reached their maximum in the climax forest community. The easily extractable GRSP/total GRSP ratio was the largest at the shrub community stage, indicating that glomalin degradation was the lowest at this stage. Ecological stoichiometry revealed N-limitation decreased and P-limitation increased with increasing vegetation restoration age. Soil enzymes had a significant impact on the GRSP production, directly and indirectly affecting nutrient metabolism balance. Conclusions: Further study of arbuscular mycorrhizal fungi to identify changes in their category and composition is needed for a better understanding of how soil enzymes affect their release of GRSP, in order to maintain a nutrient balance along successive stages of vegetation restoration.

Climate warming and high-intensity human activities threaten the stability of alpine meadow ecosystems. The stability of the soil microbial community is crucial for maintaining ecological service function. However, the effects of warming and litter removal on microbial interactions, community-building processes, and species coexistence strategies remain unclear. In this study, we used a fiberglass open-top chamber to simulate global change, and moderate grazing in winter was simulated by removing above-ground litter from all plants in the Qinghai–Tibet Plateau, China, to investigate the effects of warming, litter removal, and interactions on soil microbial communities. The treatments included (1) warming treatment (W); (2) litter removal treatment (L); (3) the combined treatment (WL); and (4) control (CK). The results show that compared with the control treatment, warming, litter removal, and the combined treatments increased bacterial Shannon diversity but reduced fungal Shannon diversity, and warming treatment significantly changed the bacterial community composition. Warming, litter removal, and the combined treatments reduced the colinear network connectivity among microorganisms but increased the modularity of the network, and the average path distance and average clustering coefficient were higher than those in the control group. Stochastic processes played a more important role in shaping the microbial community composition, and soil–available phosphorus and soil ammonium contributed more to the βNTI of the bacterial community, while total phosphorus and NAG enzyme in the soil contributed more to the βNTI of the fungal community. Notably, litter removal counteracts the effects of warming on bacterial communities. These results suggest that litter removal may enhance bacterial community stability under warming conditions, providing insights for managing alpine meadow ecosystems in the context of climate change.

Plant–soil interactions are increasingly recognized as a key driver of plant invasion, yet whether soil legacy effects associated with invaded habitats differentially influence invasive and native plants across broad geographic ranges remains poorly understood. We hypothesized that soil legacy effects would differ among soil sources from different latitudes and would affect the two species asymmetrically. Here, we address this gap by examining how latitudinal variations in soil legacy effects alter the growth and photosynthetic performance of both invasive Alternanthera philoxeroides and the co-occurring native Digitaria sanguinalis. We collected soil samples from 40 A. philoxeroides-invaded plots spanning 21° N to 37° N in China and pooled soils from five geographically adjacent sites at similar latitudes, generating eight composite soil sources (clusters 1–8, from low to high latitudes). We then conducted pot experiments with the soils originating from different latitudinal clusters to examine the effects of soil legacies on the morphology, biomass, nutrient content, and photosynthetic fluorescence of A. philoxeroides and D. sanguinalis. We found that soil legacy effects increased the maximum stem length and leaf area of D. sanguinalis, while they decreased the overall root–shoot ratio of plants at low and middle latitudes. Soil legacy effects altered the nitrogen–phosphorus ratio (N:P) of A. philoxeroides in most latitudinal clusters, with a pronounced shift toward greater phosphorus investment. In latitudinal cluster 8, soil legacy effects resulted in higher F₀ and F_m values in D. sanguinalis than in A. philoxeroides under monoculture, indicating stronger PSII reaction center activity in the native species. In mixed culture, soil legacy effects eliminated the photosynthetic superiority of A. philoxeroides over D. sanguinalis. With increasing latitude, soil legacy effects shifted the photosynthetic fluorescence characteristics of the two studied species from being associated with plant growth to being associated with ecological stoichiometry. Our study indicates that soil legacy effects in A. philoxeroides-invaded habitats may not consistently promote A. philoxeroides invasion. Instead, their regulation of A. philoxeroides and D. sanguinalis performance is latitude-dependent. These findings provide a new perspective for understanding the geographic variation in mechanisms underlying plant invasion.