Climate-soil interactions improve the stability of grassland ecosystem by driving alpine plant diversity

The grassland ecosystem plays an important role in maintaining ecological security. This study intends to better understand the effects of climate-soil interaction on the alpine grassland ecosystem and to further deepen the understanding of plant diversity and its influencing factors in the alpine meadow, alpine steppe, and desert steppe of the Qilian Mountains of China. Therefore, the soil nutrient contents such as soil organic carbon, nitrogen, available phosphorus, ammonium nitrogen, and nitrate-nitrogen were measured from the uppermost 0–40 cm soil layer. In addition, the regional vegetation characteristics were also investigated and plant diversity index values were determined. The three grassland types showed obvious variations in soil nutrient content and plant diversity index values. Alpine meadow and alpine steppe showed the highest plant diversity and soil nutrients, evident by greater soil organic carbon and nitrogen contents compared to the desert steppe. With the increase in precipitation amounts, the plant height and number of typical plants increased, but no significant impact of elevation was found. Plant diversity was positively correlated with annual precipitation and soil organic carbon, which were the primary factors determining plant diversity in the Qilian Mountains. Compared to other grassland types, alpine meadows showed the most complex network, indicating the greatest ecological stability and strong resistance to environmental changes. These findings revealed a close link between the species diversity, soil nutrients, and major climatic factors in the Qilian Mountains, which are critical for predicting plant diversity in the context of climate change