Alpine meadow degradation depresses soil nitrogen fixation by regulating plant functional groups and diazotrophic community composition

Biological nitrogen fixation (BNF), a function performed by diazotrophic microbes, plays an essential role in (N) bioavailability terrestrial ecosystems. However, little is known about the effects of meadow degradation on soil BNF and communities alpine meadows. We investigated changes their potential drivers meadows along gradient Tibetan Plateau (non-degraded, lightly degraded, moderately severely degraded meadows) using real-time quantitative PCR amplicon sequencing. Soil rates decreased significantly with range 17.34–79.84 nmol C2H4 g?1 dry d?1 across all sites. The highest rate non-degraded was 1.5–4.6-fold higher than that abundance diversity diazotrophs measured nifH Shannon also meadows, accompanied decreases plant biomass, moisture, nutrient content (C, N). correlated content, (including Nostoc, Scytonema, Rhodopseudomonas, unidentified genera within Rhizobiales Proteobacteria). community composition differed markedly among sites different levels degradation, both autotrophic (Cyanobacteria) heterotrophic (Proteobacteria) contributing to BNF. functional groups, particularly sedge family, were primary via mediating (dissolved organic C N), gene abundance, composition. Our results reveal main during emphasize importance groups shaping regulating rate. This information can be applied restoration