黄土高原坡地退耕恢复草地的土壤水分动态

Soil Water Dynamics of Degraded Grassland on the Slope of the Loess Plateau

为了解黄土高原水蚀风蚀区坡地退耕还草后的土壤水分消耗与补充过程,利用2003年开始的野外坡面径流小区定位观测土壤剖面水分,分析坡地退耕还草多年后的土壤水分动态变化及丰水年的恢复状况。结果表明:坡地退耕还草后,土壤水分含量降低,多年以后,苜蓿地显著低于坡耕地,含水量已接近或者达到萎蔫含水量。撂荒草地土壤水分含量稍低于坡耕地,尽管坡耕地有较多的径流,但是土壤水分含量保持在较高水平。2010年初3个处理土壤剖面平均含水量分别为7.4%,12.6%,12.5%,丰水年降水可以不同程度的补充土壤剖面水分,补充深度较一般年份深110cm左右,苜蓿地、撂荒地、坡耕地土壤水分分别恢复到10.0%,14.5%,15.5%,分别增加了35.1%,15.1%,24.0%。因此,坡耕地退耕种植紫花苜蓿(Medicago sativa)导致土壤水分含量显著降低,只有在丰水年土壤水分含量才有较明显的恢复。

In order to understand the soil water depletion and replenishment after returning farmland to grassland on the sloping in the water-wind erosion region of the Loess Plateau,soil moisture dynamics were observed under different land use types.Results show that the soil water content of the grassland（alfalfa）decreased distinctly and water content was close to the wilting point after alfalfa was planted for many years.Despite of having more runoff,the soil water content was in a higher level in the farmland.The average water contents of grassland,abandoned land and farmland were 7.4%,12.6% and 12.5% at the beginning of the growing season in 2010,respectively.Soil water was recharged to different levels under different land use types in the wetter year,and the recharging depth in the wetter year was deeper than normal year.The soil water contents of alfalfa land,abandoned land and farm land were restored to10.0%,14.5%,15.5%,and the soil moisture increased by 35.1%,15.1%,24.0%,respectively.As a result,the soil water content decreased significantly by returning farmland to grassland,and the distinct recovery of soil water content was observed only in the wetter year.