Effects of growing season warming on Stipa przewalskyi and Artemisia sacrorum communities and soil nutrients on the Loess Plateau

To explore the change patterns of dominant species in grasslands and their supporting mechanisms of soil nutrients under global warming, we selected the dominant species Stipa przewalskyi and Artemisia sacrorum in a typical grassland in the Loess Plateau: Yunwu Mountain National Nature Reserve in Ningxia. We aimed to explore the changes in aboveground biomass of two dominant species as well as soil organic carbon (SOC), total nitrogen, available phosphorus (AP), microbial biomass carbon, microbial biomass nitrogen (MBN), nitrate nitrogen, and ammonium nitrogen content in different soil layers under growing season warming. We found that: 1) Growing season warming increased the aboveground biomass of the two communities by 122.87% and 36.65%, respectively. The differences in the responses to warming between the two communities may be related to the different utilization characteristics of phosphorus and other nutrients. 2) The average temperature in different soil layers increased by 2.03～2.93 ℃ under experimental warming, and the increment in the surface layer (0－5 cm) was higher than that in the deeper layers. Furthermore, we found that warming caused a decrease in soil moisture content. 3) Surface soil nutrients of the S. przewalskyi and A. sacrorum communities responded more strongly to warming than their deeper counterparts; in particular, the SOC content of the surface soil was significantly reduced by 18.47% and 2.35% (P < 0.05), respectively. In addition, in the S. przewalskyi community, warming significantly increased the AP content in the surface soil and reduced the MBN content (P < 0.01). In short, growing season warming influences soil nutrient status and aboveground biomass of the S. przewalskyi and A. sacrorum communities by affecting soil temperature and water conditions, whereas S. przewalskyi community is more sensitive to these changes. The findings of the present study are of great significance for understanding the characteristics of community variation and soil nutrient cycles of different dominant species in grassland ecosystems on the Loess Plateau under global changes.