Community-level foliar stable carbon isotope is more influenced by leaf functional traits under drought conditions

The carbon isotope composition of leaf tissue is an excellent indicator of a plant's intrinsic water use efficiency, providing crucial insights into vegetation dynamics under global climate change. However, in arid and semiarid grassland ecosystems, the factors driving variations in community foliar δ ¹³ C values across different steppe types and the extent to which they can be used to monitor changes in community productivity remain unclear. Based on the community-weighted mean foliar δ ¹³ C (foliar δ ¹³ C _CWM ) values of meadow steppe, typical steppe, and desert steppe, which are distributed from east to west as water resources decrease in Inner Mongolia grasslands, our study examines the impacts and regulatory pathways of the community-weighted means of leaf functional traits (LFT _CWM ) and environmental factors on foliar δ ¹³ C _CWM values and aboveground productivity. Our results show that the foliar δ ¹³ C _CWM variations are predominantly influenced by environmental factors in meadow and typical steppe areas but by leaf traits in desert steppe areas. Aboveground productivity in Inner Mongolian grasslands is influenced primarily by temperature, and foliar δ ¹³ C _CWM values can be used to monitor changes in productivity. Our findings are crucial for understanding how plants drive processes in grassland ecosystems and determining the responses of grassland ecosystems to environmental changes.