Evapotranspiration Of The Populus Euphratica Forest In Desert Riparian And Its Response To Environmental Factors

Ejina Banner populus euphratica forest,located in China's Inner Mongolia region,is one of the three great poplars in the world,which is precious natural and cultural resources for us.Because the P.euphratica forest growed in both sides of the Ejina river,and the climate there struggle with infrequent rains,the forest also known as the desert riparian forest.The desert riparian forest ecosystem is very fragile.Serious degradation of forests caused by overusing water have taken place in the history.Research on evapotranspiration(ET)is crucial for understanding the water consumption characteristic of the P.euphratica forest.Based on the data that we measured in the Qidaoqiao P.euphratica forest reserve in Ejina Banner in the lower reach of the Heihe River,we observed the actual ET using the eddy-covariance method and analyzed the diurnal and phenological variations of the environmental factors and ET,and analyzed how did the environmental factors effect ET.The evapotranspiration of the P.euphratica forest showed a bell curve in the diurnal variation in 2016.ET values peaked at about twelve to thirteen o'clock.The peak value of the fruiting period is the highest,and value of the leaf sprouting period is lowest.The evapotranspiration was highly correlated with net radiation,soil heat flux,and was positively correlated with the air temperature,and was less relevant to the wind speed.The ET was negatively correlated with relative humidity.All the environmental factors could explain80.2% of common circadian variation of evapotranspiration in the whole growing season.The phenological variation of ET of the P.euphratica forest had a wavy changing trends,which was increased firstly and then decreased.Total ET value was 882.188 mm during the growing seasons in 2016.Daily ET value ranged from 2.064 to 9.621 mm,and the average was 5.583 mm.Some discussions on the influences of several relative environmental factorswere conducted.The calculation results showed that the order of the effect was as follows: air temperature,net radiation,soil heat flux,relative humidity,soil temperature and wind speed.Factors of air temperature,net radiation and relative humidity fit the equation : ET = 2.782 + 0.090 Ta + 0.007Rn-0.022 RH.