Nitrogen deposition does not change stochastic processes of soil microbial community assembly under climate warming in primary forest

Soil microbial communities are essential for ensuring forest health, however, the influences of global change on soil microbial communities and their ecosystem functions remain unclear. Here, we explored the influences of experimental warming (3 °C above average soil temperature) and nitrogen addition (5 g N m−2 year−1) on soil microbial biodiversity, community composition, and community assembly in an old-growth subtropical forest. Our findings showed that when the temperature was increased experimentally, there was a decrease in microbial alpha diversity, along with a decline in soil moisture and an elevation in soil temperature. The experimental treatments had not significantly influence microbial beta diversity and community composition relative to the control. Stochastic processes governed fungal and bacterial community assembly in all treatments. In addition, nitrogen addition and warming increased stochastic processes, and warming plus nitrogen addition decreased stochastic processes in bacterial community assembly. Nitrogen addition increased stochastic processes, while warming and warming plus nitrogen addition decreased stochastic processes in fungal community assembly. Overall, microbial beta diversity, community composition, and community assembly were less altered under warming and nitrogen addition, indicating that microbial communities could be resistant to short term global climate changes in an old-growth subtropical forest