不同植被类型对毛乌素沙地背风坡土壤水分时空变化的影响

在陕西省神木市毛乌素治沙造林基地，选取固定沙丘背风坡4种典型植被为对象，利用CNC503DR型中子仪对0~300 cm土壤水分进行测定，分析不同植被类型条件下固定沙丘背风坡土壤水分特征。结果表明:1）在植被类型上，固定沙丘背风坡0~300 cm剖面平均土壤含水量表现为草地>紫穗槐>长柄扁桃>沙柳；在季节变化上整体表现为，秋季>夏季>春季（2018年）、春季>夏季>秋季（2019年）。2）背风坡土壤剖面上土壤水分存在明显的分层结构，可将0~300 cm分为0~50、50~100、100~200 cm和200~300、50~300 cm各土层植被类型间土壤水分存在显著差异(P<0.05)。3）0~50 cm土层时间变系数较大，随着土层深度增加土壤水分时间变异系数逐渐减小；4种植被类型垂直变异系数夏秋季较大，春季较小；时间稳定性表现为沙柳>草地>长柄扁桃>紫穗槐。4种植被类型0~300 cm土层平均土壤含水量无显著差异，草地、长柄扁桃和沙柳土壤水分时间稳定性较强，合理的林草空间搭配有利于该区背风坡土壤水分的保持。

Effects of Different Vegetation Types on Temporal and Spatial Variation of Soil Moisture on Leeward Slope of Mu Us Sandy Land

The objectives of this study were to reveal the temporal and spatial variation of soil moisture under different vegetation types on leeward slope of fixed dune on MU Us Desert and to provide theoretical basis for rational vegetation construction in this area.Four typical vegetations on the fixed dunes of leeward slopes were selected,which were located within the afforestation base established by Shenmu Ecological Association of Shanxi Province in Mu Us Desert.A neutron probe (model CNC503DR) was used to measure the moisture of 0-300 cm soil layer from March 2018 to October 2019 to reveal the characteristics of the soil moisture.The results showed that 1) in terms of vegetation types,the average soil water content in the 0-300 cm soil profile of fixed dune leeward slope was in the order of grassland>Amorpha fruticosa>Amygdalus pedunculata>Salix psammophila.The seasonal variation of soil water content of different vegetation types was in the order of Autumn>Summer>Spring (2018); Spring>Summer>Autumn (2019).2) Soil moisture had obvious stratification structure on soil profile of leeward slope,the 0-300 cm soil layer of the four vegetation types could be divided into 0-50,50-100,100-200,and 200-300 cm.There were significant differences in soil moisture between vegetation types in 50-300 cm soil layer (P<0.05).3) The 0-50 cm layer presented high time variation coefficient that decreased with soil depth.The vertical variation coefficient of four vegetation types was larger in summer and autumn,but smaller in spring.The temporal stability of soil moisture in different vegetation types was in the order of A.fruticosa>A.pedunculata>S.psammophila>grassland.There was no significant difference in average soil water content between 0-300 cm layer in the four vegetation types (P>0.05).The time stability of the soil water in grassland,A.pedunculata and S.psammophila was relatively strong,and the reasonable collocation of forest and grass space was beneficial to the soil water conservation in the leeward slope of this area.