西北干旱区典型固沙植物夜间耗水及其影响因素

Nighttime Water Use and Its Influencing Factors for Typical Sand Binding Plants in the Arid Region of Northwest China

利用热平衡包裹式Flow32茎干液流仪和环境要素监测系统研究了河西走廊中段典型固沙植物梭梭（Haloxylon ammodendron）、白刺（Nitraria tangutorum）、沙拐枣（Calligonum mongolicum）夜间液流活动特征,分析影响3种植物夜间耗水的主要环境因素及其利用途径。结果表明：（1）梭梭、白刺、沙拐枣茎干夜间液流密度在前半夜（20：00～0：00）较大且迅速降低,在后半夜（0：00～6：00）仍有微弱液流密度且波动较大;梭梭、白刺、沙拐枣的夜间液流密度差异极显著,平均夜间液流密度依次为3.73、1.12、6.07g·cm^-2·h^-1,且在典型降雨天气条件下3种植物夜间液流活动明显减弱。（2）在观测期间,总夜间耗水量与基茎显著相关,但3种植物夜间耗水分配在不同月份间差异不显著;梭梭、白刺、沙拐枣夜间耗水对日总耗水贡献率变化范围分别为1%～30%、0.1%～16%和1.5%～20%。（3）饱和水汽压差和风速仅能解释梭梭、沙拐枣、白刺夜间液流密度24%、25%、27%的变化,3种植物夜间液流主要用以茎干补水。

Independent measurements of sap flow in stems of Haloxylon ammodendron,Nitraria tangutorum and Calligonum mongolicum and environmental variables using a commercial sap-flow gauges and micrometeorological monitoring system,respectively,were made to study nighttime sap flow activities and its influencing factors,and to estimate the nighttime water consumption for an H.ammodendron stand in an oasis-desert ecotone,located in the middle range of Hexi Corridor,Northwest China.（1）Nighttime sap flow density for these species was high before 0 oclock and decreased quickly,it was weak and fluctuated dramatically between 0 oclock and 6 oclock.We found nighttime sap flow densities between these species were very significant （P〈0.01）,and the mean value for H.ammodendron,N.tangutorum,and C.mongolicum was 3.73,1.12,and 6.07 g·cm^-2·h^-1,respectively.The results showed that sap flow density of three species all decreased in typical rainy days.（2）The total nighttime water use for these species was close related to the stem diameter during the study period （R2=0.92）,and it was not significant difference between different months （H.ammodendron,P〉0.05;N.tangutorum,P〉0.05;C.mongolicum,P〉0.05）.We found that H.ammodendron contributed 1% to 30% nighttime water use to daily total water,N.tangutorum contribute 0.1% to 16%,and C.mongolicum conribute 1.5% to 20%,respectively.（3）We presumed that nighttime sap flow for these species were mainly used to refilling because VPD and wind speed only explained 24%,25% and 27% of their variation,respectively.