不同类型生物土壤结皮覆盖下风沙土的入渗特征及模拟

干旱荒漠区广泛分布的生物土壤结皮(BSCs)对土壤水分入渗过程有重要影响。以古尔班通古特沙漠南缘的BSCs为研究对象,基于野外采样与室内模拟实验等方法,探究藓类、地衣和藻等3种类型BSCs覆盖下沙土的入渗特征。结果表明:与无结皮覆盖的风沙土对照,3种类型BSCs均显著降低了沙土初渗速率,藓类结皮、地衣结皮、藻结皮覆盖下初渗速率降低幅度依次为36.10%、46.42%、50.39%;藓类结皮、地衣结皮(P0.05)和藻结皮(P0.05)均明显降低了沙土稳渗速率,降低幅度依次为16.50%、33.98%和35.92%;3种类型BSCs均限制了湿润锋在沙土的推进过程,表现为:藓类结皮、地衣结皮、藻结皮的渗漏时间分别为裸沙对照的2.13、3.04和2.98倍;各类型BSCs均减小了沙土累积入渗量,阻碍了沙土水分入渗,与裸沙对照相比,藓类结皮、地衣结皮、藻结皮的1 h累积入渗量分别降低16.10%、28.56%和26.56%。在实验条件下,Kostiakov模型最适用于模拟不同类型BSCs覆盖下土壤水分入渗过程,Horton模型模拟效果次之。

Characteristic and numerical simulation of sandy soil infiltration under the different types of biological soil crusts

In arid areas, soil water condition is the key factor for the desert ecosystem. An important part of the hydrologic cycle, infiltration is the only way for precipitation and surface water transfer to soil water. Soil water infiltration capacity profoundly affects the redistribution of precipitation, and is of crucial importance for the storage and utilization of precipitation. The Gurbanttunggut Desert is the largest fixed and semi-fixed desert in China. It is covered by well-developed biological soil crusts(mosses, lichens, alage, fungi, cyanobacteria and bacteria). In recent years, a number of studies have focused on the influence of biological soil crusts on the process of soil infiltration, but areas of uncertainty remain in the process. In this study, three typical types of biological soil crusts (moss, lichen and algal crusts) in the Gurbantunggut Desert were selected and an indoor soil column was used to simulate experiments to examine the effect of biological soil crusts on the process of soil infiltration, including changes in the infiltration rate, wetting front movement and cumulative water infiltration. The results indicated that the effect of biological soil crusts on soil water infiltration was significant. Firstly, all three types of biological soil crusts decreased the initial infiltration rate significantly, but they differed in the degree of the reduction. The moss crusts, lichen crusts and algal crusts decreased the initial infiltration rates by 36.10%,46.42% and 50.39% respectively. The moss, lichen(P<0.05)and algal crusts(P<0.05) also can decreased the stable infiltration rate by 16.50%,33.98% and 35.92% respectively. Secondly, movement of wetting front was slower in soils covered with these three types of biological soil crusts than in bare soil. The leakage time of soil under moss, lichen and algal crusts were respectively 2.13, 3.04, and 2.98 times that of bare soil. Thirdly, all three types of biological soil crusts reduced the cumulative infiltration volume. Relative to the bare soil, the reduction rates of moss, lichen and algal crusts are 16.10%,28.56% and 26.56% respectively. In simulated laboratory experiments, three typical models were used to simulate the water infiltration process in soils. The result showed that:In this experimental situation, the Kostiakov equation is most applicable to describe the infiltration processes of sandy soil covered by the three types of biological soil crusts. although the Horton equationwas the next best option.