中文摘要：

针对西北干旱荒漠区水分循环与生态平衡问题,利用热扩散（TDP）探针监测典型荒漠植物梭梭和柽柳的枝条和胸径的液流日变化,并分析不同尺度液流与环境因子的关系及其尺度间的转换方法。结果表明：梭梭和柽柳的枝条和胸径的液流开始时间基本与太阳辐射开始增强的时间一致,且都滞后于温度和水气压亏缺（VPD）的开始升高时间。太阳总辐射是植物液流的启动器,而VPD是植物液流的加速器。不同环境因子对梭梭和柽柳不同尺度液流的影响作用不同,整体相关性大小为：总辐射〉光合有效辐射〉温度〉VPD。梭梭枝条间差异不明显,可以较好的上推出胸径的液流密度,即梭梭枝条尺度和冠层尺度间蒸腾作用可以较好的转换：y=1.925x＋0.569,R2=0.956。柽柳枝条间差异较大,枝条液流与胸径液流间的相关性相对较小（y=2.418x＋0.808,R2=0.697）,把枝条液流上推到胸径尺度需分析不同位置的枝条间液流的差异性及其与微环境的关系,进一步修正尺度上推方程。

英文摘要：

Aiming at solving the problem of hydrological cycle and ecological balance in northwest arid desert,thermal dissipation probes（TDP） were used to monitor diurnal change characteristic of sap flow in two desert plants Haloxylon ammodendron and Tamarix chinensis in branch and canopy scales,respectively.The relationships of sap flow in different scales and environment factors,as well as up-scaling were analyzed.The results showed that the two plants sap flow start time in both scales（branch scale and canopy scale） were basically in accordance with the time of solar radiance beginning to enhance,and lagged behind the time of temperature and VPD（vapour pressure deficit） beginning to rise.Global radiance was the launcher of plant sap flow,while VPD was the accelerator.The different environment factors influenced dissimilarly on sap flow of two plants in different scales,and the correlations between environment factors and sap flow were global radiance 〉photosynthetically active radiation（PAR） 〉temperature 〉VPD.Sap flows of Haloxylon ammodendron branches which had no significant difference could be used to upscale the sap flow of the DBH.That was to say, the transpiration of Haloxylon ammodendron in different scales could transform well：y=1.925x＋0.569,R2=0.956.While sap flows of Tamarix chinensis branches which had difference could not be used very well to upscale the sap flow of the DBH：y=2.418x＋0.808,R2=0.697.Transpiration up-scaling from branch to canopy needed to analyse the different R2of sap flow of branches in different positions and the relationship with microenvironment,and modified the up-scaling formula further.