河西走廊绿洲边缘降水对土壤水分特征的影响

Effect of precipitation on soil moisture characteristics at the oasis edge of the Hexi corridor

【目的】探究干旱地区间断性和不可预知特征的降水对土壤水分特征的影响,为荒漠绿洲过渡区的生态建设和恢复提供理论依据。【方法】通过对河西走廊绿洲边缘的沙质荒漠和砾质荒漠土壤水分的长期观测,结合当地气象数据,分析降水对土壤水分特征的影响。【结果】研究区域沙质和砾质荒漠的土壤水分处于中等变异程度,沙质荒漠土壤含水量的最大值为6.61%、砾质荒漠土壤含水量的最大值为11.81%,与降水量的最大值均出现在7月,土壤水分同降水量存在正相关关系。荒漠绿洲区土壤水分在垂直空间上随着土层深度的增加,土壤水分变异系数减小,土壤水分变化由活跃逐渐趋于稳定。但降水沙质荒漠和砾质荒漠区土壤水分的影响存在显著差异,沙质荒漠土壤以自上而下的活塞式下渗为主,降水以逐层向下的方式入渗,下层土壤接受降水补给时具有滞后性。而砾质土壤各层对降水的反应迅速,能够通过大孔隙快速补给下层土壤,水分迅速入渗至深层土壤中。【结论】河西走廊绿洲边缘的土壤水分受土壤类型的影响,降水对其影响有差异,根据不同的土壤水分变化特征,科学开展生态建设和恢复,对绿洲边缘生态系统的可持续发展有重要意义。

【Objective】The effects of intermittent and unpredictable precipitation on soil moisture characteristics in arid areas were studied to provide a theoretical basis for ecological construction and restoration in transitional desert-oasis areas.【Method】Based on the long-term observation of soil moisture in sandy and gravelly deserts at the edge of the Hexi corridor,the effects of precipitation on soil moisture characteristics were analyzed.【Result】The soil moisture of sandy and gravelly deserts in the study area is in the middle range of variation.The maximum moisture content of desert and gravel desert soils is 6.61%and 11.81%respectively.The maximum values of soil moisture and precipitation both occurred in July and they showed a positive correlation.As the depth of the soil layer increases,the coefficient of variation of soil moisture decreases and the variation of soil moisture tends to be stable.However,the response of soil moisture to rainfall pulse is different in sandy desert and gravelly desert areas.The main infiltration mode of sandy desert soil is piston infiltration from top to bottom,the lower soil has hysteresis when it receives precipitation recharge.The response of each layer of gravelly soil to precipitation is rapid,and soil moisture can be quickly replenished to the lower layer through macropores to penetrate into the deep soil.【Conclusion】Soil moisture content in an oasis edge of Hexi corridor is affected by soil type and has different responses to precipitation pulses.According to different soil moisture change characteristics,ecological construction and restoration should be carried out scientifically,it is of great significance to the sustainable development of oasis edge ecosystem.