Soil Prokaryotic Community Shows No Response To 2 Years Of Simulated Nitrogen Deposition In An Arid Ecosystem In Northwestern China

An arid ecosystem might be sensitive to nitrogen (N) deposition, but the associated ecosystem-specific response of soil microbes is not well studied. To assess the N enrichment effects on plant and prokaryotic community diversity, we performed a two-year NH4NO3 treatment in a desert steppe in northwestern China. Results showed that N addition increased plant aboveground biomass and decreased plant Shannon diversity. A C-4 herb (Salsola collina) became dominant, and loss of legume species was observed. The concentrations of soil NH4+-N, NO3--N, microbial biomass N, and the plant aboveground biomass N pool increased in contrast to total N, suggesting that the N input into the arid ecosystem might mainly be assimilated by plants and exit the ecosystem. Remarkably, the alpha-diversity and structure of the soil prokaryotic community did not vary even at the highest N addition rate. Structural equation modelling further found that the plant aboveground N pool counteracted the acidification effect of N deposition and maintained soil pH thus partially stabilizing the composition of prokaryotic communities in a desert steppe. These findings suggested that the plants and N loss might contribute to the lack of responsiveness of soil prokaryotic community to N deposition in a desert steppe.