长沙地区典型树木蒸腾对环境因子的响应及模拟

Stem water potential and trunk sap flow for some typical tree species including Osmanthus fragrans, Cinnamomum camphora, Pinus massoniana and Liquidambar formosana in Changsha were monitored from 2013 to 2015. Meanwhile, the meteorological factors and soil moisture were measured in parallel. The main objects are to explore the response of transpiration to environmental factors, and to select an optimal transpiration model for this area by comparing the performance of the MJS, BTA and MBTA models. The results show that during the non-drought period, tree transpiration was less sensitive to precipitation and soil moisture. Solar radiation exerted the greatest effects on Osmanthus fragrans and Pinus massoniana transpiration with the sensitivity coefficient > 0.75, while the sensitivity of transpiration for Cinnamomum camphora and Liquidambar formosana tree to solar radiation and water vapor pressure deficit was strong. During the drought period in 2013, soil water content was the dominant factor for tree transpiration with the sensitivity coefficient > 0.71, and then tree transpiration was limited by the effects of temperature and water vapor pressure deficits. Among the three models, the MBTA model performed the best in fitting the observed tree transpiration, with a relative error was less than 5%; the BTA model failed to simulate the decline of the tree's daily transpiration during the drought period in 2013, and significantly overestimated transpiration of Pinus massoniana during the growth season in 2014 and 2015; the simulation accuracy of MJS model was not good. The performance of the three models in the growth season of 2013 was worse than that in 2014 and 2015, indicating that when the environmental stress exceeded the adaptive range of trees, the physiological structure of trees was likely to be changed, which leads to a reduction of the simulation accuracy of transpiration model constructed by environmental factors.