短期放牧对高寒草甸表层土壤入渗和水分保持能力的影响

Effect of Short-term Grazing on Surface Soil Infiltration and Soil Water Retention in Alpine Meadow

为深入揭示短期放牧对高寒草甸生态系统地表水文过程的影响机理,基于5个放牧强度(A:2.75只羊/hm^2;B:3.64只羊/hm^2;C:4.35只羊/hm^2;D:4.76只羊/hm^2;E:5.20只羊/hm^2)的3a控制放牧试验,对比研究了表层土壤(0—10cm)物理性状、入渗过程、土壤水分特征曲线及持水和供水能力对放牧强度的响应。结果表明:C处理的土壤初始含水量显著高于D、E处理,但各放牧强度的土壤容重和4个孔隙指标无显著变化;放牧改变了土壤入渗过程,随放牧强度增加,B与C处理入渗较好,D与E处理入渗较差;Gardner模型适用于放牧强度的土壤水分特征曲线拟合,相关系数均达极显著水平,且表征土壤持水性能的a值与低中吸力段含水量表明B与C处理的持水能力高于其它处理;100kPa吸力下比水容量显示,A、B和C处理较D与E处理提高了土壤供水能力。总之,合理放牧强度短期内有利于保存高寒草甸土壤含水量,增强土壤导水性和持水能力,保证土壤有效供水,降低高寒草甸生态系统的退化风险。

The paper studied the changes of soil infiltration and soil water retention under various grazing intensities in short term in alpine meadow for revealing the influence mechanism of grazing on surface hydrological process in alpine meadow ecosystem. A controlled grazing trial with 5 grazing intensities （A： 2. 75 head/ hm2, B： 3.64 head/hm^2, C： 4.35 head/hm^2, D： 4.76 head/hm^2, E： 5.20 head/hm^2） in 3 years has been conducted in Tianzhu County, Gansu. The physical properties, infiltration, water characteristic curve, water retention and water supply of topsoil （0-10 cm） were measured under 5 grazing intensities. The results showed that the initial soil moisture of treatment C was significantly higher than that of treatment D and E. However, there was no significant difference in the soil bulk density and 4 indexes of soil porosity under 5 grazing intensities. Grazing changed the process of soil infiltration, with the increase of grazing intensity both treatment B and C had good performance of soil infiltration. However, treatment D and E had poor performance of soil infiltration. Model Gardner was suitable for matching soil water retention curve because of the significant correlation coefficient. The a value and soil water content at low-middle suction segments indicated that the water holding capacities of treatment B and C were higher than those of other treatments. According to the specific water capacity under the suction of 100 kPa, treatment A, B and C had higher water supply capacity than treatment D and E. In conclusion, the rational grazing could preserve soil moisture, improve soil hydraulic conductivity and water holding capacity, and maintain soil water supply, which reduce the risk of degradation of alpine meadow ecosvstem.