Biogeographic Patterns of Leaf Stoichiometry and Adaption Strategy of Stellera Chamaejasme L. in Degraded Grasslands Across Northern China

Abstract

Background: Plant leaf stoichiometry reflect its adaptations to environments. Leaf stoichiometry variations across different environments have been extensively studied among grassland plants, but little is known about intraspecific leaf stoichiometry, especially for widely distributed species, such as Stellera chamaejasme L. We present the first study on the leaf stoichiometry of S. chamaejasme, and evaluate their relationships with environmental variables by collecting S. chamaejasme leaf and soil samples from 29 invaded sites in the two plateaus of distinct environments [the Inner Mongolian Plateau (IM) and Qinghai-Tibet Plateau (QT)] in Northern China. Leaf C, N, P, and K and their stoichiometric ratios, and soil physicochemical properties were determined, together with climate information from each sampling sites. Results: Results showed that mean leaf C, N, P, and K concentrations were 498.60, 19.95, 2.15, and 6.57 g · kg-1, respectively; the C/N, C/P, and N/P ratios were 25.46, 246.22, and 9.84, respectively. Soil physicochemical properties of S. chamaejasme invaded area varied wildly, and few significant correlations between S. chamaejasme leaf ecological stoichiometry and soil physicochemical properties were observed. Except for C and N in leaves, the P and K had higher homeostasis than 1, between 4.17 and 13.21. Moreover, C and N content of S. chamaejasme leaves were unaffected by any climate factors. However, the correlation between leaf P and climate factors was significant in IM only, while leaf K in QT. Finally, partial least squares path modeling suggested that leaf P or leaf K were affected by different mechanisms in QT and IM regions. Conclusions: Our results indicated that S. chamaejasme tend to be insensitive to variation in soil nutrient availability, resulting in their broad distributions in China grasslands. Moreover, S. chamaejasme adapt to changing environments by adjusting its relationships with climate or soil factors to improve their chances of survival and spread in degraded grasslands.