Precipitation and soil microbial community influence plant response to warming and N addition in a desert steppe

Abstract Aims Global environmental changes are known to affect terrestrial ecosystems. However, how plants and soil microorganisms respond to warming and nitrogen deposition in a desert steppe with strong seasonal drought remains largely unexplored. Methods Based on a 13-year manipulative field experiment, we investigated the effects of warming and nitrogen addition on soil microbial communities and plant net photosynthetic rates during two hydrologically contrasting months (6 mm in June and 106 mm in July) in a desert steppe in Inner Mongolia. Results We found that in the wet month, warming and nitrogen (N) addition significantly increased soil microbial biomass. Warming and N addition significantly increased soil inorganic N and increased leaf N concentration, thus promoting the net photosynthetic rate of Stipa breviflora. Moreover, warming and N addition significantly shifted soil microbial composition with an increase in soil bacterial phospholipid fatty acids (PLFAs) and reduced fungal PLFAs. The increased soil inorganic N indirectly increased leaf N and plant photosynthesis by soil microbial composition. These changes were not significant in the dry month. Conclusions Our study indicates that warming and N addition can promote plant photosynthesis by increasing soil N availability and changing the structure of the soil microbial community. These changes only occurred when there was sufficient precipitation. These results highlight the crucial role of soil water availability and the soil microbial community in influencing plant responses to global change drivers (e.g., warming and N addition).