Leaf functional traits have more contributions than climate to the variations of leaf stable carbon isotope of different plant functional types on the eastern Qinghai-Tibetan Plateau

Elucidating the mechanisms that control the leaf stable carbon isotope values (delta 13Cleaf) is the prerequisite for the wide-spread application of delta 13Cleaf. However, the competing effects of physiological and environmental factors on delta 13Cleaf variations of the different plant functional types (PFTs) have not been disentangled, and the corresponding mecha-nisms remain unclear. Based on large-scale delta 13Cleaf measurements on the eastern Qinghai-Tibetan Plateau, the relative contributions and regulatory pathways of leaf functional traits (LFTs) and climatic factors to delta 13Cleafvariations of the different PFTs were investigated. We found that delta 13Cleaf of the different PFTs was correlated with annual mean precip-itation negatively, but not a simple linear relationship with annual mean temperature and varied by PFTs. Leaf nitro-gen content per unit area and leaf mass per area (correlated with delta 13Cleaf positively) had more substantial effects on the delta 13Cleaf variations of the different PFTs than other LFTs. The relative contributions of LFTs to the delta 13Cleafvariations were greater than that of climatic factors, and the direct and indirect effects of climatic factors on delta 13Cleafvariations varied by PFTs. Our findings provide new insights into understanding key drivers of delta 13Cleaf variations at the PFT level on a regional scale.