Characteristics of sap flow of 4 typical shelter-belt tree species and it’s relationships with environmental factors in the desert region of Northwest China
Abstract:Pulse sensors based on the heat compensation theory were applied to measure the stem sap flow of 4 typical tree species in shelter-belt of the desert region in Northwest China. Wind speed, relative humidity, air temperature, soil temperature and leaf temperature were measured at an automatic weather station. The aim of this study was to investigate the diurnal variations of sap flow of different desert trees, and try to understand the characteristics of their water requirements and ecological significance. The results indicated that sap flow rate in Populus Russkii Jabl., P.euphratica Oliv. and Ulmus pumila L. have distinct diurnal variations and the sap flow rates present single-peaks curves, but Elaeagnus angustifolia L. have not been observed clear diurnal pattern in sap flow. The sap flow velocity altered with the probe-inserted depth into the stem. Sap flow velocity had significant diversity among the 4 tree species. Under sufficient soil water content, increase of irrigation can influence on the microhabitat and have an effect to reduce the transpirations. The correlation between the sap flow velocity and the meteorological factors was analyzed. The dynamics of stem sap flows could be fitted well by a regression model based on the meteorological factors. The model could be used to estimate the transpiration of the 4 tree species.