古尔班通古特沙漠南缘地下水深埋区幼龄梭梭春夏季土壤水分利用动态

The Dynamic of Soil Water Utilization in Spring and Summer of Young Haloxylon ammodendron at Deep Groundwater of Southern Edge of Gurbantünggüt Desert

梭梭是古尔班通古特沙漠的建群种,为研究梭梭水分利用特征及季节变化,于2014年5月和7月利用稳定性同位素技术测量幼龄梭梭小枝木质部水、冠下0—400cm不同土层土壤水δ18 O值,采用直接对比法、平均深度模型以及Iso-Source模型对幼龄梭梭春夏季的水分来源进行分析。结果表明:幼龄梭梭冠下0—70cm土壤含水量5月显著高于7月,70cm及以下土层土壤含水量5月、7月相差不大;表层土壤水δ18 O值变化较大,5月表层土壤水δ18 O值与7月相比显著偏小;5月各土层土壤水δ18 O值变化复杂,7月各土层土壤水δ18 O值变化单一,随深度增加逐渐减小;幼龄梭梭5月主要利用0—50cm土层的土壤水,利用比例达67.5%,7月主要利用250—400cm土层的土壤水,利用比例达94.2%。

Water is not only an important factor limiting the survival and growth of plants,but also a factor influencing the distribution and quantity of vegetation in arid areas.Haloxylon ammodendronis a dominant plant species in the Gurbantünggüt Desert.Studing the water use pattern and seasonal changes is vital for understanding plant adaptation to environmental changes in the arid zone.In this study,the oxygen sable isotope ratios（δ18 O）of xylem water and soil water in different soil layers（0—400cm）were measured,and the water resource of young Haloxylon ammodendronin spring and summer were analyzed with direct comparison method,Iso-Source model and the mean depth of water uptake model.The results show that（1）The soil water of 0—70cm in May was significantly higher than the surface soil moisture content in July,the difference of soil moisture content in 70—400cm soil layer is not significant in Spring and Summer.（2）Theδ18 O values of surface soil water changed widely.In May,theδ18 O value of surface soil water was varied and it＇s significantly more negative compared with July.In July,theδ18 O value of soil water gradually decreases with depth increases.（3）The mainly water resource of young Haloxylon ammodendronis the soil water in0—50cm soil layer in May,the use ratio is up to 67.5%.However,in July,the contribution of surface soil water decreased drastically while that deep soil water increased rapidly,the mainly water resource is the soil water in 250—400cm soil layer in July,the use ratio is up to 94.2%.