N2-fixing bacteria are more sensitive to microtopography than nitrogen addition in degraded grassland

Introduction Soil bacteria play a crucial role in the terrestrial nitrogen (N) cycle by fixing atmospheric N 2 , and this process is influenced both biotic abiotic factors. The diversity of -fixing (NFB) directly reflects efficiency soil fixation, NFB degraded alpine meadow may change with different fertilizing levels varied slopes. However, how addition affects meadows, whether influence varies slope, remain poorly understood. Methods We conducted an field experiment at three (2, 5, 10 g N·m −2 ·a −1 ) to study effects on two slopes Tibetan Plateau. Results There were significant differences dominant bacterial species between Chao1 index, richness, beta did not differ significantly slopes, but Shannon index did. Interestingly, had no effect or abundance bacteria. we observe some low-abundance NFB. community composition positively correlated slope physicochemical properties (e.g., total potassium, pH, nitrogen). Conclusions Our highlights variation communities among meadows their resilience exogenous addition. results also underscore importance considering micro-topography microbial future studies ecosystems.