Sapflow Dynamics And Environmental Responses Of Grape And Poplar In Arid Oasis

Agricultural water consumption is the main way of water resources consumption in arid areas.With the increasing imbalance between agricultural and ecological water supply and demand,the crisis of water resources has become an urgent problem to be solved at present.Understanding the transpiration mechanism of grape and poplar is great significance for establishing sustainable water resources management scheme and promoting harmonious development of economy and ecological environment in arid oasis area.Based on the measured data about sap flow of grape and poplar,meteorological factors,eddy covariance and physiological indexes in 2017 at Dunhuang Ecological Hydrological Station.This paper studied the sap flow dynamics of grape and poplar in growing season and its response to environmental factors,analyzed the difference of sap flow between two species at night,established a prediction model of sap flow based on meteorological factors by using multiple regression method.The results showed that:(1)The sap flow of both species showed seasonal variation.But the sap flow of poplar was significantly higher than that of grape during growing season,and it showed " midday depression " at the peak of the light.For these two species,it was not single positive correlation between diameter at breast height and daily transpiration.(2)The diurnal variation of grape sap flow under different weather conditions basically showed that the sunny days exceed cloudy days and rainy days.Although the sap flow of poplar is the highest in sunny days,it will rise rapidly with the increase of net radiation and vapor pressure deficit in cloudy and rainy days.There was a time lag between the sap flow and meteorological factors in both species,in sunny days the sap flow peak lagging behind relative humidity,but ahead of atmospheric temperature,vapor pressure deficit and net radiation.(3)The ratio of nocturnal transpiration to daily total transpiration of grape and poplar in growing season was 4.9% ± 4.4% and 14.0% ± 4.3%.Both atmospheric temperature and vapor pressure deficit were strongly correlated with grape’s nighttime sap flow,considering that stomatal opening at night causes nighttime transpiration.The nighttime sap flow of poplar mainly plays the role of storing water in the stem(4)The multivariate regression equation based on atmospheric temperature,vapor pressure deficit and net radiation was able to simulate the transpiration of the two species well,but it was underestimated compared with the measured data.The daytime simulated transpiration of grape and poplar accounted for 78.9% ± 10.6% and 81.6% ± 5.0% of the measured data.In this study,the transpiration and water consumption patterns of grape and poplar in arid oasis area were comprehensively grasped by using advanced techniques such as thermal diffusion,eddy correlation and micro-meteorological observation,which provided a certain basis for guiding the rational allocation of agricultural and ecological water resources,improving the water use efficiency in the arid region.