Ecophysiological adaptability of four tree species in the southern subtropical evergreen broad-leaved forest to warming

Abstract

Aims The subject of this study was to investigate warming effects on leaf stomatal traits, anatomical structure and photosynthetic traits of four common tree species in subtropical evergreen broad-leaved forest of southern China, and to compare their physiological adaptability to warming. Our study aims to provide a theoretical basis for better predicting the tree growth of native forests in a warming climate.Methods One-year-old seedlings of Syzygium rehderianum, Ormosia pinnata, Castanopsis hystrix and Schima superba were selected and exposed to two levels of temperature (ambient temperature and infrared heater warming). Leaf stomatal traits, anatomical structure and photosynthetic characteristics were measured to represent the abilities of stomatal regulation, leaf tissue regulation and nutrient maintenance, respectively.Important findings For Syzygium rehderianum, warming decreased its leaf sponge tissue thickness, photosynthetic nitrogen-use efficiency (PNUE) and photosynthetic phosphorous-use efficiency (PPUE). Seedling of O. pinnata exposed to warming showed increased stomatal conductance, photosynthetic rate, PNUE and PPUE, but decreased stomatal density, leaf thickness and palisade tissue thickness. For C. hystrix, warming decreased the stomata size, but did not affect its photosynthetic rate. Seedling of Schima superba exposed to warming showed lower stomata density, leaf palisade tissue thickness, photosynthetic rate, PNUE and PPUE, but higher stomata size. These results suggested that O. pinnata, Syzygium rehderianum and Schima superba could reduce their leaf thickness to acclimate to warming conditions. The abilities of stomatal regulation, nutrient maintenance, photosynthetic rate and PNUE varied among these tree species. Warming would be beneficial for the growth of O. pinnata due to increased photosynthetic rate, PNUE and PPUE, while not for Syzygium rehderianum and Schima superba, the two dominant tree species of native forests. This study indicated that, with projected climate change, O. pinnata may replace Syzygium rehderianum and Schima superba as a new dominant tree species in the subtropical evergreen broad-leaved forest for its stronger adaptability to warming.