Responses of soil microbial community structure under litter to changes in precipitation and nitrogen addition in a desert steppe

Soil microorganisms are essential in maintaining terrestrial ecosystem function and are central drivers of soil-plant nutrient cycling. However, relatively few studies have explored the impact of precipitation and nitrogen (N) addition on soil microbial community structure beneath litter. In this study, we conducted a field simulation control experiment on litter decomposition under varying precipitation regimes (normal, increased by 30 %, and decreased by 30 %) and N addition levels (0 and 10 g m⁻² y⁻¹) in the desert steppe of Yanchi County, China. Our findings revealed that changes in precipitation and N addition promoted litter decomposition and caused the accumulation of soil nutrients. Specifically, N addition significantly increased nitrate nitrogen (51.95 %), ammonium nitrogen (42.92 %), soil organic carbon (6.81 %), and total phosphorus (7.82 %)(P＜0.05), decreased precipitation significantly elevated contents of nitrate nitrogen (26.80 %), total nitrogen (24.47 %), soil organic carbon (37.62 %), total phosphorus (22.78 %), and microbial biomass C (33.20 %) (P＜0.05). N addition decreased microbial biomarkers content by 1.13 %, but increased microbial diversity indices (Shannon-Wiener index (1.53 %), Brillouin diversity index (0.54 %), Pielou evenness index (1.12 %), Simpson dominance index (0.91 %), Mcintosh diversity index (1.11 %)) (P＜0.05). Meanwhile, decreased precipitation significantly enhanced microbial biomarkers content by 5.83 % and diversity indices (Shannon-Wiener index (3.67 %), Brillouin diversity index (2.16 %), Pielou evenness index (1.55 %), Simpson dominance index (1.82 %), Mcintosh diversity index (2.63 %)) (P＜0.05). We indicated the decreased precipitation enhanced the effect of N addition on microbial community and diversity, while increased precipitation showed the opposite trend. Redundancy analysis highlighted MBC as a critical factor influencing microbial community structure, accounting for 35.3 % of the variation (P＜0.01). This study provides valuable insights into managing and conserving desert steppe ecosystems.