Spatial patterns of leaf nitrogen and phosphorus stoichiometry across southeast to central Tibet

Leaf N and P stoichiometry in terrestrial ecosystems has been widely investigated in recent years owing to the importance of these elements in improving the predicted vegetation responses to global changes. The vertical distribution of leaf N and P stoichiometry has attracted increasing attention because of the dramatic changes in environmental factors at regional scales. However, the characteristics of leaf N and P stoichiometry in the southeast Qinghai-Tibet plateau (SET) are not clear, although this area is sensitive to global change. Here, we analyzed the leaf N and P concentrations in dominant plant species on natural altitudinal gradients on the Duoxiongla (DXL), Sejila (SJL), Mila (ML), and Gangbala (GBL) mountains across the SET all the way to central Tibet. Our results showed that the leaf N concentrations were comparable among the regions, whereas the leaf P concentrations dramatically decreased from SET to central Tibet (CT). The leaf N concentrations were 23.6, 21.3, 20.8, and 22.4 g kg, and the leaf P concentrations were 2.40, 2.49, 1.94, and 1.59 g kg on the SJL, DXL, ML and GBL mountains, respectively. The leaf N/P ratios on the DXL, SJL, ML, and GBL mountains were 8.81, 10.3, 11.2, and 14.2, respectively. Considering the increasing trend of the leaf N/P ratio from southeast Qinghai-Tibet plateau to central Tibet, N limitation might widely exist in well vegetated ecosystems in the Qinghai-Tibet plateau.