六道沟流域2种典型灌木不同季节水分来源及利用效率

Water Source and Water Use Efficiency of Two Typical Shrubs in Different Seasons in Liudaogou Watershed

该试验以黄土高原风蚀水蚀区的典型代表六道沟流域为研究区,选取了2种典型灌木柠条(Caragana korshinskii)和沙柳(Salix psammophila)为研究对象,测定其茎秆水和不同层次土壤水分的δD值及叶片的δ^(13) C值,利用IsoSource模型分析2种植物对不同层次土壤水分的利用比例,并同步测定叶片水势、气孔导度、光合速率和蒸腾速率等生理生态因子,分析2种灌木在不同季节的水分来源及生理生态适应机制。结果表明:(1)柠条和沙柳的水分利用策略随季节波动,在不同季节对不同土层水分的利用比例存在差异。(2)旱季柠条和沙柳主要利用40~80cm土层的土壤水,利用比例分别为48.1%和49%。(3)雨季柠条主要利用表层0~10cm和浅层10~40cm的土壤水分,利用率约为57.5%;雨季沙柳主要利用浅层10~40cm的土壤水,利用比例达76%。(4)旱季柠条和沙柳的水分亏缺严重,其叶片水势、气孔导度、光合速率和蒸腾速率均小于雨季,而水分利用效率均大于雨季。研究发现,柠条和沙柳在旱季均主要利用深层土壤水分,雨季更倾向于利用浅层土壤水分;柠条和沙柳均能够通过降低气孔导度减小水分损失来获得较高的碳同化速率,维持较高的水分利用效率以适应干旱环境,均表现出较强的适应能力。

Water is the main limiting factor for plant growth in the water-wind erosion area of the Loess Plateau.Liudaogou watershed was taken as a study area in consideration of its typical representative of the Loess Plateau.Caragana korshinskii and Salix psammophila,two kinds of typical shrubs,were chosen as the objects of the study to measure theδD of their stem water and soil water in different soil depths and δ^（13） C of the leaves.And the IsoSource model was used to calculate the probable contributions of soil waterto these two shrubs.In addition,the leaf water potential,stomatal conductance,photosynthetic rate and transpiration rate were measured to compare the different water sources and eco-physiological adaption of the two shrubs in different seasons.The results showed that：（1）the water use strategies of C.korshinskii and S.psammophilachanged with seasonal fluctuations,and the soil moisture utilization ratio of different depths in different seasons were significantly different.（2）In the dry season,C.korshinskii and S.psammophila mainly used the water from 40-80 cm layer,and the ratio was 48.1%and 49%respectively.（3）In the wet season,C.korshinskii used more than 57.5% water from the surface soil layer（0-10 cm）and shallow layer（10-40 cm）,while S.psammophilaused more than 76% water from shallow layer（10-40 cm）.（4）The soil water deficit of the two shrubs were serious in the dry season,and the leaf water potential,stomatal conductance,photosynthetic rate and transpiration rate were less than those in the wet season.It indicates that the C.korshinskii and S.psammophilacan obtain higher carbon assimilation rate by reducing stomatal conductance to decrease water loss.And they can maintain higher water use efficient to adapt the arid condition.