摘要 : Abstract Plant–microbial interaction for nitrogen (N) is important in plant growth, soil fertility, and function of grasslands. However, it remains unclear how plant–microbial competition for N changes after the restoration of deg... 展开 Abstract Plant–microbial interaction for nitrogen (N) is important in plant growth, soil fertility, and function of grasslands. However, it remains unclear how plant–microbial competition for N changes after the restoration of degraded alpine grasslands. This study aimed to explore the dynamics of plant–microbial competition for N in restoration chronosequences (i.e., short-, medium-, and long-term) in an alpine meadow and an alpine steppe on the Qinghai–Tibetan Plateau. Two inorganic forms of N (ammonium (NH4+) and nitrate (NO3?)) and one organic N (glycine) were used for the in situ 15N labeling experiments. The competition between microorganisms and plants (i.e., ratios) for N increased by 4.8 times after medium- than short-term restoration in the alpine meadow and remained stable after each restoration. Compared to short-term restoration, medium-term restoration increased the N uptake of microorganisms by 2.4 times in alpine meadow and 4.3 times in alpine steppe. Microorganisms and plants showed chemical niche differentiation between NH4+ and NO3? uptake in both alpine ecosystems after medium-term restoration, with microorganisms taking up more NH4+ but plants taking up more NO3?. Competition between microorganisms and plants decreased after long-term compared with medium-term restoration, maintaining the microbial to plant N uptake ratio?>?1. Long-term restoration increased plant N uptake in the alpine meadow, while decreased the microbial N uptake in the alpine steppe. Neither microorganisms nor plants showed a preference for glycine, but glycine uptake by microorganisms was higher than plants after medium- and long-term restorations. These findings provide valuable insights into the restoration of degraded alpine grasslands from the perspective of plant–microbial competition for available N in soil, which may be useful for developing sustainable grassland management practices. 收起