腾格里沙漠人工固沙植被区浅层土壤水分对降水和生物结皮的响应

选择腾格里沙漠东南缘人工植被区3种典型的地表覆被类型（藓类结皮、藻类结皮和流沙）土壤为对象，选取发生在7月和9月的两次降水事件，研究浅层土壤（3、5、10 cm）水分入渗与再分布过程。结果表明：浅表层3 cm深度土壤水分在降雨初期均表现为跳跃式增加，而在降雨中后期由于土壤剖面不同深度水势梯度减小，降水入渗速率降低，土壤水分仅呈现小幅波动。在两次降水事件中，藓类结皮和藻类结皮对降水入渗的阻碍作用比较显著，入渗速率表现为沙土 > 藻类结皮 > 藓类结皮；从水分再分布看，生物土壤结皮的存在致使水分再分配过程表现出明显的浅层化；降水过程结束后，结皮促进水分的蒸发损失，从而减少植被可利用水分含量。人工固沙植被区广泛发育的生物土壤结皮对降水入渗与再分布过程以及土壤水量平衡具有重要影响。

Response of Soil Moisture in Shallow Depth to Stochastic Rainfall and Biological Crust in Revegetated Sand Dunes in the Tengger Desert,China

An experiment to measure water balance associated with infiltration events was conducted on the revegetated sand dunes in the Tengger Desert, north-western China. We choose three land cover types (Moss dominated soil crust, Algae dominated soil crust and dune sand) to study the effects of land cover change on infiltration, soil water redistribution and evaporation under different conditions of rainfall events on 8^th July and 30^th September, 2015, respectively. The results showed that surface soil moisture changed remarkably at the early stage of rainfall occurrence with a sharp increase within three hours, whereas, soil moisture exhibited a slight fluctuation at the later stage of rainfall resulted from the decrease of soil water potential gradient. In general, the presence of moss and algae dominated soil crusts impede the rainfall infiltration, limiting the depth to which rainwater can infiltrate and/or redistribute. Furthermore, biological crust could increase evaporation. We may conclude that the land cover with different biological soil crust had significant effects on soil hydrological processes, inducing more shallow distributed soil water in the revegetated sand dunes.