Sap Flow In Stem Of Populus Euphratica In Alagan, The Lower Reaches Of Tarim River

From April to October 2013, the Granier method for estimating the stem sap flow was applied to study Populus euphratica in Alagan, the lower reaches of Tarim River. The relationship between the stem sap flow and environmental factors were analyzed.(1)The stem sap flow of Populus euphratica presented a single-peaked curve with an obvious circadian rhythmicity and fluctuated with environment factors. The average daily sap flow rate of Populus euphratica with a DBH(diameter at breast height) of 52.06 cm was 15.14 L?h-1.(2)In July 20 th of the typical sunny day, the average stem sap flow rate of Populus euphratica with DBH of 32.58 cm, 29.13 cm and 20.23 cm were 15.35 L?h-1、12.44 L?h-1 and 4.10L?h-1, respectively. There is a positive correlation between the sap flow rate in stems and the DBH.(3)The daily accumulation process of the stem sap flow of Populus euphratica showed "S" type. In the night, the water consumption is less, and the stem sap flow accumulation curve rised slowly, and in the daytime had the opposite situation. The stem sap flow rate of Populus euphratica was decreased by a declining groundwater table.(4)The environmental factors such as PAR(photosynthetically active radiation)、wind speed、 air temperature and relative humidity were the main factors affecting the stem sap flow rate, and the dynamics of stem sap flow could be predicted by the liner regression model based on PAR and wind speed.(5)The process of water consumption curve in the whole growth season of Populus euphratica presented a single-peaked curve,July is the biggest month of the water consumption;with DBH32.58,29.13,20.23 cm the average daily water consumption of Populus euphratica were211.68,165.50,53.20L;in the whole growth season,the average daily water consumption of Populus euphratica were 138.20,108.72,29.54 L. Populus euphratica has strong environmental adaptability. Populus euphratica brings down internal temperature through transpiration to maintain normal life activities when temperature rises. Because of the extremely arid environment, Populus euphratica had a relatively higher stem sap flow rate and a great water consumption.