[Differences and drivers of leaf stable carbon and nitrogen isotope in herbs under different vegetation types on the eastern Qinghai-Tibet Plateau].

The natural abundance of stable carbon and nitrogen isotopes (δ ¹³ C and δ ¹⁵ N) in leaves can provide comprehensive information on the physiological and ecological processes of plants and has been widely used in ecological research. However, recent studies on leaf δ ¹³ C and δ ¹⁵ N have focused mainly on woody species, few studies have been conducted on herbs in different vegetation types, and their differences and driving factors are still unclear. In this study, we focused on the herbs in subalpine coniferous forests, alpine shrublands, and alpine mea-dows on the eastern Qinghai-Tibet Plateau, and investigated the differences in leaf δ ¹³ C and δ ¹⁵ N of herbs and the driving factors. The results showed that there were significant differences in leaf δ ¹³ C and δ ¹⁵ N values of herbs among different vegetation types, with the highest δ ¹³ C and δ ¹⁵ N values in alpine meadows, followed by alpine shrublands, and the lowest in subalpine coniferous forests. Using variation partitioning analysis, we revealed that differences in leaf δ ¹³ C and δ ¹⁵ N of herbs among various vegetation types were driven by both leaf functional traits and climate factors, with the contribution of leaf functional traits being relatively higher than that of climate factors. Hierarchical partitioning results indicated that mean annual temperature (MAT), chlorophyll content index, leaf nitrogen content per unit area (N _area ), and leaf mass per area were the main drivers of leaf δ ¹³ C variations of herbs across different vegetation types, while the relative importance of N _area and MAT for variation in leaf δ ¹⁵ N of herbs was much higher than those other variables. There was a strong coupling relationship between leaf δ ¹³ C and δ ¹⁵ N as indicated by the result of the ordinary least squares regression. Our findings could provide new insights into understanding the key drivers of leaf δ ¹³ C and δ ¹⁵ N variations in herbs across different vegetation types.