毛乌素沙地地下水浅埋区沙柳蒸腾对降水的响应

Response of Salix psammophilatranspiration to precipitation at shallow groundwater area in Mu Us Desert

【目的】研究毛乌素沙地地下水浅埋区沙柳蒸腾对降水的响应,为确定该地区植被用水来源提供依据。【方法】2011-05-29-07-13,在毛乌素沙地海流兔河流域,运用包裹式树干径流仪测定沙柳枝条的蒸腾量,并监测同期的气象要素、土壤含水率及地下水水位的变化;基于监测数据,分析沙柳蒸腾量在降水过程中的变化及蒸腾量与降水量、土壤含水率和地下水水位的相关性。【结果】1)降水过程中净辐射迅速减小,导致沙柳蒸腾量迅速减少甚至为0。2)降水后的沙柳蒸腾量较降水前有所增加,但最大蒸腾量出现的时间不同,且蒸腾量与降水量之间呈非线性关系。3)沙柳潜在蒸腾量解释了65%的蒸腾量变化,表明沙柳蒸腾主要受潜在蒸腾量的控制。4)土壤水和地下水均为沙柳的蒸腾水源。【结论】在毛乌素沙地的地下水浅埋区,沙柳蒸腾量与降水量呈非线性关系,土壤水和地下水是沙柳的蒸腾水源。

【Objective】This study aimed to investigate the response of Salix psammophila transpiration to precipitation at shallow groundwater area in Mu Us Desert and to identify water sources for vegetation use.【Method】From May 25 to Jun 13,2011,field experiment was conducted in the Hailiutu River basin.S.psammophila transpiration was measured by Sap Flow32K.Weather conditions,soil water contents,and groundwater levels were recorded synchronously.【Result】（1） Transpiration of S.psammophila bush decreased during rain events because of the decrease of net radiation.（2） Transpiration of S.psammophila bush increased slightly after rain events,but the maximum of transpiration occurred differently and the relationship between rainfall amount and transpiration rate was nonlinear.（3） Potential evapotranspiration explained 65% changes of transpiration of S.psammophila bush,acting as the dominating factor of transpiration.（4） The transpiration sources of S.psammophila included both soil water and groundwater.【Conclusion】At the shallow groundwater area in Mu Us Desert,nonlinear relationship between sap flow of S.psammophila bush and rainfall amount was observed,both soil water and groundwater were sources for transpiration of S.psammophila.