干旱半干旱区退化草地土壤水分变化及其对降雨时间格局的响应

降雨是干旱半干旱地区的主要水分来源,降雨量、降雨时长和降雨强度等共同影响降雨入渗,进而影响降雨对地表下不同土层的补充。研究干旱半干旱区退化草地生态系统不同土层土壤水分对不同量级降雨时间格局的动态响应变化,对于揭示水土关键要素、草地荒漠化防止及应对气候变化的影响均具有重要意义,基于2018年连续对锡林郭勒盟正镶白旗额里图牧场的降雨及地表下5,15,30,60,100 cm的土壤体积含水率数据的观测,探讨了各土层土壤水分变化及其对降雨事件大小的响应。结果表明:对于干旱半干旱区草地而言,降雨可以显著影响5-60 cm的土层土壤水分;随着土层加深,相同降雨过程引起的土壤水分增量呈降低趋势,0-10,10-20 cm土层土壤水分增量明显,小于3,6,20,50 mm的降雨不能到达地表以下5,15,30,60 cm土层;高降雨强度、降雨前较高的土壤含水率有利于雨水的下渗,5-60 cm土层的土壤水分增量与降雨强度、土壤初始含水率以及二者交互作用均呈显著或极显著线性关系,100 cm土层的土壤水分增量与降雨强度、土壤初始含水率以及二者交互作用均无显著线性关系,且30,60 cm土层土壤水分增量只在无雨日间隔极短且降雨量很大的情况下有明显波动。

Soil Moisture Changes in Degraded Grassland and Its Response to Rainfall Temporal Pattern in Arid and Semi-arid Areas

Rainfall is the main source of water in arid and semi-arid areas. Rainfall, rainfall duration and rainfall intensity all affect rainfall water infiltration, which in turn affects the replenishment of rainfall to different soil layers under the surface. It is important to study the dynamic response of soil moisture in different soil layers to different rainfall patterns in arid and semi-arid areas to reveal the key elements of water and soil, grassland desertification prevention and climate change responses. Through the continuous observations of the rainfall and the volumetric water content data of 5, 15, 30, 60 and 100 cm below the soil surface in the Xilin Gol League, and the changes of soil moisture in each soil layer and their response to the rainfall events were studied. The results showed that for grassland in arid and semi-arid areas, rainfall could significantly affect the soil moisture in soil layer of 5-60 cm; with the deepening of soil layer, the soil moisture increment caused by the same rainfall process showed a decreasing trend. The increase in soil moisture in 0-10 cm and 10-20cm soil layer was obvious, while if the rainfall was less than 3, 6, 20, 50 mm, water could not reach the 5, 15, 30 and 60 cm soil layers. The heavier rainfall intensity and the higher soil moisture content before rainfall were favorable for the rain water infiltration. The increase of soil moisture in 5-60 cm soil layer had significant or extremely significant linear relationship with rainfall intensity, initial soil moisture content and their interaction. But there was no significant linear relationship in 100 cm soil layer. The soil moisture increments in the 30 and 60 cm soil layers occurred only when the rain-free day interval was extremely short or the rainfall was very large.