沙漠人工植被区生物结皮类土壤的蒸发特性——以沙坡头沙漠研究试验站为例

EVAPORATION FROM SOILS COVERED WITH BIOLOGICAL CRUSTS IN REVEGETATED DESERT——A CASE STUDY IN SHAPOTOU DESERT RESEARCH AND EXPERIMENT STATION

沙漠人工植被区的建立有助于生物结皮的形成和发育,它将显著改变植被区土壤的持水性能和蒸发过程。利用室内蒸发法研究了流沙和沙漠植被区生物结皮类土壤的蒸发特性。结果表明,随固沙年限的延长生物结皮层及其下的亚土层逐年增厚、容重下降、土壤持水能力增加,且苔藓结皮优于藻类结皮。当土壤样品完全饱和后,生物结皮土壤的蒸发量明显高于流沙,苔藓结皮高于藻类结皮,并随固沙年限的延长而增加;但是蒸发过程表现出明显的阶段性(p<0.05)。在蒸发的第一阶段(速率稳定阶段),与流沙相比生物结皮的存在有利于蒸发;但在蒸发的第二阶段(速率下降阶段)生物结皮却抑制蒸发。分析后认为,正是生物结皮具有较高的持水能力,在蒸发的第一阶段增加了水分被蒸发的可能性;当土壤干旱时,结皮可以将水分束缚在土壤中从而抑制了蒸发。

Development of biological crusts resulting from establishment of artificial vegetation in the desert will significantly change water holding capacity and evaporation process of the soil. An indoor evaporation method was used to study evaporation characteristics of the soils covered with or without biological crusts. Results show that the longer the history of sand dune fixation, the thicker the biological crusts and the sub-soil layer below them, the lower its bulk density, and the higher the soil water holding capacity; which was more significant with moss-crust-covered soil than algae-crust-covered. And so was it in terms of soil evaporation rate after the soils were saturated with water. The process of evaporation, however, could be clearly divided into three stages （p 〈 0.05）. In the first stage （constant in evaporation rate）, biological crusts contributed to evaporation, but in the second stage （declining in evaporation rate）, they inhibited evaporation. Based on analysis, it is held that it is the higher waterholding capacity of the biologic crusts that enhance the possibility of soil water evaporation at the first stage, and inhibit evaporation by holding water in the soil when the soil gets dried up.