Variations in leaf morphological traits of Quercus guyavifolia (Fagaceae) were mainly influenced by water and ultraviolet irradiation at high elevations on the Qinghai-Tibet Plateau, China

Abstract

Leaf morphological traits vary along elevational gradients so that plants can adapt to their surrounding habitat. However, the abiotic factors that shape those traits are still debatable, especially for plants at high elevations where the environment can be very harsh. Quercus guyavifolia H. Léveillé (Fagaceae) is a woody plant found along the southeastern boundary of the Qinghai-Tibet Plateau. Distribution elevations of the species range from 2000 m to 4500 m approximately, providing an excellent opportunity to explore correlations among leaf traits and environmental factors. We used multiple-regression models to investigate spatial trends in leaf morphology and their environmental determinants. As elevation increased, values for leaf area, length, width, the ratio of leaf length to width, shape factor, and petiole length and width decreased significantly and all were positively correlated with mean annual precipitation. Leaf length, the ratio of leaf length to width, and petiole length were negatively correlated with the daily mean maximum intensity of ultraviolet (UV)-B irradiation during the growing season. Our results indicated that the amounts of both precipitation and UV irradiation largely shape the leaf morphology in Q. guyavifolia along the elevation gradient. This study provides evidence for the adaptive plasticity of leaves in response to environments in regions at high elevations.