荒漠绿洲湿地土壤优先流与水分入渗特征

Characteristics of preferential flow and water infiltration in desert oasis wetland

地表水分、溶质和污染物以土壤优先流的形式下渗到深层土壤或地下水中,将导致土壤养分流失与地下水污染等问题。因此,土壤优先流研究将为干旱区荒漠绿洲湿地水分运移与盐分积累过程提供理论依据。以荒漠绿洲湿地为研究区,选取柽柳灌丛、盐碱草地和杨树林,以道路为对照,采用室外染色示踪法对湿地土壤优先流特征与水分入渗进行研究。结果表明:不同植被类型土壤优先流入渗深度存在显著差异,其柽柳灌丛和盐碱草地几乎是杨树林和道的2倍;染色面积比随深度的增加而波动下降,0—20 cm土层染色面积比占总染色面积的54.42%—89.27%;染色路径宽度以20—250 mm和>250 mm为主;优先流类型以高相互作用混合流和非均质指流为主。在荒漠绿洲湿地,砾石促进土壤优先流发生,增加了侧向流;同时,粗根的减少抑制了优先流的发生;此外,土壤盐分通过影响土壤大孔隙分布而影响水分入渗过程。因此,荒漠绿洲湿地土壤优先流与水分入渗差异是土壤质地、根系分布与盐分离子共同作用的结果。

Surface moisture,solutes and pollutants infiltrate into deep soil or groundwater in the form of preferential flow,which will lead to soil nutrient loss and groundwater pollution.Therefore,the soil preferential flow study may provide a theoretical basis for the process of moisture transport and salt accumulation in the desert oasis wetland in arid areas.In this paper,Tamarix chinensis,Saline-alkali grassland and Poplar forest were selected as the study area in desert oasis wetland,and path were taken as control.The characteristics of soil preferential flow and moisture infiltration were studied by outdoor dyeing tracer method.The results showed that there was a significant difference in the infiltration depth of the soil between different vegetation types.The tamarix chinensis and saline-alkaline grassland were almost twice as large as that of poplar forest and path.The staining area ratio fluctuated with the increase of depth.The staining area in 0—20 cm soil layer accounted for 54.42%—89.27% of the total staining area.The dyeing path width was mainly 20—250 mm and >250 mm.The preferential flow types is dominated by highly interacted macropore flow and heterogeneous figure flow.In desert oasis wetland,gravel promoted the occurrence of soil preferential flow and increased lateral flow.At the same time,the decrease of coarse roots inhibited the occurrence of preferential flow.In addition,soil salinity affects the process of water infiltration by affecting the distribution of soil macropores.Therefore,the difference between soil preferential flow and water infiltration in desert oasis wetland is the result of soil texture,root distribution and salt segregation.