Nighttime sap flow and its driving forces for Populus euphratica in a desert riparian forest, Northwest China  

作　　者：SI Jianhua FENG Qi YU Tengfei ZHAO Chunyan 

机构地区：[1]Alxa Desert Eco-hydrology Experimental Research Station, Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences [2]Gansu Hydrology and Water Resources Engineering Center

出　　处：《Journal of Arid Land》2015年第5期665-674,共10页干旱区科学（英文版）

基　　金：supported by the Major Research Plan of the National Natural Science Foundation of China (91025024);the Key Project of the Chinese Academy of Sciences (KZZD-EW-04-05);the West Light Foundation of the Chinese Academy of Sciences

摘　　要：Nighttime sap flow is a potentially important factor that affects whole-plant water balance and water-use efficiency （WUE）. Its functions include predawn disequilibrium between plant and soil water potentials as well as between the increments of oxygen supply and nutrient uptake. However, main factors that drive nighttime sap flow remain unclear, and researches related to the relationship between nighttime sap flow velocity and environmental factors are limited. Accordingly, we investigated the variations in the nighttime sap flow of Populus euphratica in a desert riparian forest of an extremely arid region, Northwest China. Results indicated that P. euphratica sap flow occurred throughout the night during the growing season because of the partial stomata opening. Nighttime sap flow for the P. euphratica forest accounted for 31%-47% of its daily sap flow during the growing season. The high value of nighttime sap flow could be the result of high stomatal conductance and could have significant implications for water budgets. Throughout the whole growing season, nighttime sap flow velocity of P. euphratica was positively correlated with the vapor pressure deficit （VPD）, air temperature and soil water content. We found that VPD and soil water content were the main driving factors for nighttime sap flow of P. euphratica.Nighttime sap flow is a potentially important factor that affects whole-plant water balance and water-use efficiency （WUE）. Its functions include predawn disequilibrium between plant and soil water potentials as well as between the increments of oxygen supply and nutrient uptake. However, main factors that drive nighttime sap flow remain unclear, and researches related to the relationship between nighttime sap flow velocity and environmental factors are limited. Accordingly, we investigated the variations in the nighttime sap flow of Populus euphratica in a desert riparian forest of an extremely arid region, Northwest China. Results indicated that P. euphratica sap flow occurred throughout the night during the growing season because of the partial stomata opening. Nighttime sap flow for the P. euphratica forest accounted for 31%-47% of its daily sap flow during the growing season. The high value of nighttime sap flow could be the result of high stomatal conductance and could have significant implications for water budgets. Throughout the whole growing season, nighttime sap flow velocity of P. euphratica was positively correlated with the vapor pressure deficit （VPD）, air temperature and soil water content. We found that VPD and soil water content were the main driving factors for nighttime sap flow of P. euphratica.

关 键 词：nighttime sap flow stomatal conductance vapor pressure deficit driving factors desert riparian forest 

分 类 号：S792.11[农业科学—林木遗传育种]