毛乌素沙地圪丑沟小流域沙柳水分利用来源研究

为探究毛乌素沙地典型治沙植物根系吸水来源及其影响因素,通过测定毛乌素沙地圪丑沟小流域沙柳(Salix psammophila)(18~20年)木质部水及其各种潜在水源(降水、土壤水和地下水)的氢氧同位素组成(δD和δ¹⁸ O),利用多元线性混合模型(IsoSource)研究沙柳水分来源的季节变化特征及其影响因素。结果表明,监测期间(6-11月)沙柳木质部水、降水、土壤水和地下水的δD值变化范围分别为-82.41‰~-52.91‰,-144.81‰~-6.60‰,-96.94‰~-42.65‰和-86.42‰~-71.82‰,δ¹⁸ O值变化范围分别为-10.77‰~-7.29‰,-18.86‰~-2.07‰,-12.85‰~-0.79‰和-10.86‰~-9.74‰。雨季(7-9月)降雨量和土壤含水量分别高于旱季(6,10,11月)24.80~90.10 mm和0.95%~1.84%,但6-9月地下水位却低于10-11月2~7 cm。沙柳根系在旱季6月主要利用深层土壤水(>200 cm)(33.70%)和地下水(26.20%),雨季(7-9月)逐渐转变为以吸收浅层土壤水(<200 cm)为主(50.70%~54.00%),10-11月由于气温降低、降水减少及沙柳生命活动减弱,浅层土壤水(<200 cm)对沙柳根系吸水的贡献高于雨季(7-9月)35.20%~40.00%,而地下水对沙柳根系吸水的贡献显著降低(<5.00%)。因此,沙柳根系对于毛乌素沙地季节性干旱具有较强的适应和调节能力,其吸水来源随降雨量、土壤含水量和地下水位季节波动而变化。

Water Use Source of Salix psammophila in Gechougou Small Watershed of Mu Us Sandy Land

The hydrogen and oxygen isotopic compositions(δD andδ18 O)of stem water and its potential sources(rain water,soil water,and groundwater)were measured monthly from June to November,2018 in a Salix psammophila forest(18~20 years)in Gechougou watershed of Mu Us Sandy Land.The dynamic changes and controls of root water source were studied by the multiple linear mixed model(IsoSource).Results showed that the variation range ofδD were-82.41‰~-52.91‰,-144.81‰~-6.60‰,-96.94‰~-42.65‰,and-86.42‰~-71.82‰for stem water,rain water,soil water,and groundwater,respectively.The variation range ofδ18 O were-10.77‰~-7.29‰,-18.86‰~-2.07‰,-12.85‰~-0.79‰,and-10.86‰~-9.74‰,respectively,during the monitored period(June-November).Rainfall amount and soil water content in the rainy season(July—September)were 24.80~90.10 mm and 0.95%~1.84%higher than that in the dry season(June,October,and November).However,the groundwater level during June to September were 2~7 cm lower than that in October and November.In June,S.psammophila mainly used deep soil water(>200 cm)(33.70%)and groundwater(26.20%).From July to September,the root water source mainly came from shallow soil water(<200 cm)(50.70%~54.00%).Compared with the rainy season(July—September),the contribution of shallow soil water(<200 cm)to root water source remarkably increased by 35.20%~40.00%in October and November due to the low air temperature,rainfall amount,and weak life activity of S.psammophila.There was a significant reduction in the use of groundwater in October and November(<5.00%).Therefore,S.psammophila is adaptable to the seasonal drought and is suitable for desertification control in the Mu Us Sandy Land.The root water source of S.psammophila changed with seasonal variations of rainfall amount,soil profile water content,and groundwater level.