Interactive effects of nitrogen fertilizer and altered precipitation on fungal communities in arid grasslands of northern China

Fungi play an essential role in regulating the functioning of terrestrial ecosystems and are sensitive to climate change factors. Climate change incidents, such as N deposition and altered precipitation, create abiotic stress regarding the water use efficiency of soil and nutrient limitation impacting the activity of soil fungi. This study aimed to examine the combined effects of N fertilization and altered precipitation on soil fungal diversity and composition in the desert steppe. In the present study, we carried out a field experiment to assess the soil fungal diversity and composition of the desert steppe in response to N fertilizer (0 or 35 kg N ha−1 year−1) and precipitation changes (control, − 50% precipitation, or + 50% precipitation) in the desert steppe. The study was initiated in 2012, and plant and soil samples were collected after 5 years (August, 2017) of field treatments. High-throughput sequencing was applied to estimate the fungal diversity and composition. The soil fungal communities were dominated by Ascomycota (87.85% ± 1.26%), which primarily drove the fungal community composition. Decreased precipitation promoted strong shifts in fungal community composition under both N fertilizer levels. Increased precipitation significantly reduced Shannon-Wiener indices by 9.96%. The increasing relative abundances of fungal functional groups (lichenized saprotroph, animaland plant pathogens) resulted in a marked shift in fungal community composition from decreased precipitation to increased precipitation, which is attributed to the important role of the Ascomycota phylum in fungal communities. Structural equation modeling (SEM) indicated that C4 biomass was the predominant factor determining the Shannon-Wiener index for these fungi. Direct altered precipitation, indirect soil pH, and C4 biomass together controlled soil fungal community composition, with altered precipitation as the main driver. The interactive effects of N fertilizer and altered precipitation on grassland plant density, biomass, and soil properties may play an essential role in determining fungal diversity and community composition. Precipitation is a primary limiting factor that influences fungal community composition. Effects of N fertilizer on soil fungal community composition are highly dependent on changes in precipitation.