Abstract:

Understanding the regional pattern of leaf stoichiometry and its contributing variables are of importance for predicting plant responses to global change and modelling the productivity and nutrient fluxes of ecosystems. In this study, we investigated leaf stoichiometry of plants that sampled from Hexi Corridor, a typical arid region in China, and tried to explore the contribution variables on leaf stoichiometry along the geographic, climatic, and soil gradients.

In August 2012, 70 sites in Hexi Corridor were investigated. Plant leaves and soils from five equivalent plots within each site were sampled. C, N, and P contents of leaf and soil were measured.

Compared with leaf N and P contents in regional and global scales, leaf N content in Hexi Corridor was close to them with the value of 20.19 mg g-1, while leaf P content was lower than them with the value of 1.34 mg g-1. Overall, leaf N:P value in Hexi Corridor was 15.70. Individually, leaf N:P values of shrubs and herbs were 16.81 and 14.80, respectively. Scaling exponents for leaf N vs. P of overall and shrubs in Hexi Corridor were 1.29, higher than the scaling exponent of herbs (1.08). Leaf stoichiometry of shrubs and herbs did not show significant latitudinal and longitudinal patterns, meanwhile, it has no significant correlation with mean annual precipitation (MAP), mean annual temperature (MAT), and soil elements. However, only leaf stoichiometry of herbs has significant correlation with altitude and aridity degree. These results indicate that plants in Hexi Corridor are possibly co-limited by N and P, while shrubs are mainly limited by soil P and herbs are limited by soil N. Scaling relationship reveals that leaf N vs. P of herbs is isometric. With increasing altitude, the quadratic regression for leaf C and N contents and the linear regression for leaf P content of herbs reflect the difference responses of the three elements on the variation of MAT along the altitude and it could be explained by plant physiology hypothesis and biogeochemical hypotheses. With decreasing aridity, leaf N and N:P of herbs increased significantly, inferring that herbs growth would be limited by P increasingly and strengthening the increasing nitrogen availability with increasing precipitation. In conclusion, different altitude and aridity patterns for leaf stoichiometry of herbs and shrubs reveal the plastic survive strategies of different xerophytes in Hexi Corridor. Moreover, leaf stoichiometry of herbs in Hexi Corridor could be as indicator of the changing environment that caused by aridity.

Key words: leaf stoichiometry, shrubs, herbs, aridity, Hexi Corridor