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 (δ ¹³ C _leaf ) is the prerequisite for the widespread application of δ ¹³ C _leaf . However, the competing effects of physiological and environmental factors on δ ¹³ C _leaf variations of the different plant functional types (PFTs) have not been disentangled, and the corresponding mechanisms remain unclear. Based on large-scale δ ¹³ C _leaf measurements on the eastern Qinghai-Tibetan Plateau, the relative contributions and regulatory pathways of leaf functional traits (LFTs) and climatic factors to δ ¹³ C _leaf variations of the different PFTs were investigated. We found that δ ¹³ C _leaf of the different PFTs was correlated with annual mean precipitation negatively, but not a simple linear relationship with annual mean temperature and varied by PFTs. Leaf nitrogen content per unit area and leaf mass per area (correlated with δ ¹³ C _leaf positively) had more substantial effects on the δ ¹³ C _leaf variations of the different PFTs than other LFTs. The relative contributions of LFTs to the δ ¹³ C _leaf variations were greater than that of climatic factors, and the direct and indirect effects of climatic factors on δ ¹³ C _leaf variations varied by PFTs. Our findings provide new insights into understanding key drivers of δ ¹³ C _leaf variations at the PFT level on a regional scale.
Competing Interests: Declaration of competing interest The authors assert that we have no financial or other non-financial interests that could influence the reported in this paper.
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