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.

Automated summary

Nitrogen enrichment in a desert steppe was found to increase plant aboveground biomass and alter plant diversity, while the response of soil prokaryotic communities remained stable. The plant aboveground N pool counteracted the acidification effect of N deposition, maintaining soil pH and contributing to the stability of prokaryotic communities in the desert steppe. The lack of responsiveness of soil prokaryotic communities to N deposition was suggested to be influenced by plant dynamics and N loss in the ecosystem.