Atmospheric nitrogen (N) deposition and climate warming significantly influence soil nitrogen transformation processes. Nitrification, a key step in the N cycle, is primarily driven by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, their responses to environmental changes in warm-temperate shrub tussock grasslands—a major grassland type in China—remain poorly understood. In this study, we examined the effects of N addition and warming on the community composition of ammonia oxidizers and soil nitrification potential (NP) through pot experiments simulating field conditions. Our results demonstrated that (1) the AOB community was more responsive to N addition and warming than AOA, with the genus Nitrosospira increasing by 6.30–21.75% under treatments; (2) soil pH increased significantly under warming (from 6.53 to 6.86) but remained unchanged under N addition; (3) NP increased significantly under all treatment conditions, most markedly under warming alone (2.83-fold increase compared to the control); and (4) NP was positively correlated with both soil pH and the relative abundance of Nitrosospira. These findings suggest that warming and N deposition enhance nitrification in shrub tussock soil by altering AOB community structure and increasing soil pH. This study provides new insights into the microbial mechanisms driving N cycling in warm-temperate grasslands under global change.

Invasive plants often alter biological soil conditions to increase their own competitiveness. Through indoor simulated nitrogen deposition culture experiments, we investigated the differences in growth indicators and nutrient content levels between the invasive plant Cenchrus spinifex Cav. and the native symbiotic plant Agropyron cristatum (L.) Gaertn. under diverse nitrogen application modes and planting-competition ratios. Furthermore, we examined the alterations in key microbial communities involved in soil nitrogen cycling of C. spinifex. The results indicated that the invasion of C. spinifex could inhibit the growth of native plants, and in fact altered the accumulation and transformation processes related to soil nitrogen, resulting in reduced rates of soil nitrogen transformation. The overarching aim of this research was to construct a theoretical foundation for the scientific comprehension of the invasion mechanisms of C. spinifex, in order to better prevent the further spread of this invasive plant and mitigate its pernicious impact on the current environment.

Soil bacterial diversity often shows different trends due to changes in dominant plant species. However, the potential key drivers of processes that reveal bacterial diversity per se have not been clearly elucidated. We established a field experiment with 9 native grassland species and assessed the relationship between soil bacterial diversity and ecological taxa classified by network construction. A co-occurrence network of 1065 points and 10023 edges, among 9 native grasses, was established to classify microbial ecological taxa. The results showed that the relative abundance of ecological taxa classified as peripherals, which is influenced by soil urease activity, inhibited bacterial diversity. Conversely, the relative abundance of specific taxa directly controlled by plants was positively related to bacterial diversity. Further, the composition of peripherals was not affected by soil physicochemical properties, while the composition of specific taxa was affected by NO₃^-, TP, AP, SU, TC and AK. The composition of peripherals and specific taxa have different responses to soil properties due to their sensitivity to environmental changes. Our findings reveal that plant-dominated bacterial diversity is closely linked to the abundance of peripheral and specific taxa. Understanding these mechanisms may provide a new insight in to the management of grassland soil microbes through the selection of grass species following disturbance and subsequent restoration.

The reintroduction of grassland plant species is widely used to restore degraded cropland, yet the species-specific effects on soil microbial diversity remain poorly understood. Understanding how individual plant species shape microbial communities is critical for improving restoration outcomes. To address this, we established experimental plots with 11 plant species on abandoned cropland and evaluated their impacts on soil bacterial diversity. Our results revealed marked variations in soil bacterial diversity across species. Richness indices (ACE and Richness) were positively correlated with soil total phosphorus (TP) and pH, while evenness indices (Simpson and Pielou) were negatively correlated with the proportion of water-stable aggregates (WSA). By classifying soil bacteria into ecological groups via co-occurrence network analysis, we found that bacterial diversity was positively correlated with the relative abundance of keystone and low-frequency taxa, but negatively correlated with peripheral taxa and other taxa. Further analysis indicated that stochastic processes following plant reintroduction promoted the emergence of low-frequency taxa, while deterministic processes contributed to a higher relative abundance of other taxa. Taken together, these findings suggest that species such as Elymus sibiricus (E. sibi) enhance soil bacterial diversity by shifting community assembly toward more stochastic processes, accompanied by an increase in low-frequency taxa and a reduction in the relative abundance of other taxa. Our results provide critical insights for selecting plant species that enhance microbial diversity for the restoration of abandoned cropland. Graphical Abstract Our study demonstrates a dual-pathway mechanism by which plant species regulate soil bacterial diversity: (i) by modifying soil properties (e.g., pH, TP, WSA), which filter the microbial community; and (ii) by modulating the abundance and assembly of key ecological groups within the microbial network. The selection of plant species determines the balance between these pathways, ultimately shaping the diversity outcome.

Nitrogen deposition continuously alters the invasibility of terrestrial ecosystems, but how the composition of local plant functional groups regulates this process by root-associated microbial during invasion, especially under the background of resource changes, remains unclear. This study focused on the invasive plant Cenchrus spinifex Cav. and conducted an interactive experiment using nitrogen addition and four different functional group combinations of local plant communities. The results show that the community with the closest phylogenetic distance (PD = 189) had the strongest resistance to invasion. Nitrogen addition was the core factor driving invasion (total effect 0.86), which promoted invasion by increasing soil nitrogen pools and altering microbial community structure. The role of leguminous plants changed fundamentally with nitrogen availability; they were competitors under low-nitrogen conditions, while under high-nitrogen conditions, they transformed into “synergistic invaders” by shaping the root-associated environment rich in microorganisms such as Proteobacteria that facilitate rapid nutrient turnover. Plant nitrogen and phosphorus content (PNP) is a key indicator reflecting the nutrient absorption capacity of invasive plants and is closely related to invasion success. It significantly promotes the ability of root resources acquisition. The study shows that invasion success depends on the dynamic balance among resource input, the phylogenetic background of the local community, and the microbial feedback regulated by it. Future ecological management should consider the coordinated regulation of aboveground functional group selection and underground microbial processes.