黄土高原沟壑区不同植被对土壤水分分布特征影响

Impacts of Vegetation Types on Soil Water Distributions in Loess Hilly Region

为探讨黄土高原不同植被类型下土壤水分分布特征,揭示其生态水文效应,以长武县王东沟小流域定位监测小区为研究对象,于2013年5月—2014年4月使用中子仪法对坡面4种植被覆盖类型(草地、沙棘、油松、沙棘油松混交林)下0—500cm深剖面上土壤水分进行了完整水文年的实际观测。结果表明:(1)草地平均土壤含水量显著高于沙棘、油松、沙棘油松混交林地(p<0.05)。草地小区平均土壤水分含量随深度呈增加趋势,而沙棘、油松和沙棘油松混交林地表现为增加—减少—增加的倒"S"型;(2)500cm剖面上,草地和油松林地土壤水分变异系数小于沙棘和油松沙棘混交林地。4种植被覆盖类型下土壤水分都表现出春、冬积累和恢复,夏、秋消耗的季节性规律;(3)降雨量对0—200cm的土壤水分贮量具有明显影响,200—500cm土壤贮水量较为稳定,植被类型的不同增加了土壤储水量的差异。可见,草地土壤水分含量相对较高,变异性小;其他乔灌木植被类型土壤含水量相对较低,变异性大。降雨量的输入和温度的变更使土壤含水量的变化无论在剖面上还是随着时间进展具有一致性,而植被类型的影响则是在这种一致性基础上增大土壤含水量对降雨和温度的响应。

In order to understand the effects of vegetation on soil water content and investigate the ecohydrological processes,four vegetation types（grassland,Hippophae rhamnoides L.,Pinus tabuliformis Carr.,mixed forest of Hippophae rhamnoides L.and Pinus tabuliformis Carr.）in four runoff plots were investigated in Wangdong Watershed,Changwu County,Shaanxi Province.Neutron moisture meter was used to estimate the soil water content along 0—500 cm soil profile in a hydrological year from May 2013 to April 2014.The results showed that：（1）the average soil water content under the natural grass was significantly higher than that in the other three vegetation types,while it did not show significant difference among the vegetation types with Hippophae rhamnoides L.,Pinus tabuliformis Carr.and mixed forest of Hippophae rhamnoides L.and Pinus tabuliformis Carr.;the average soil water content under the natural grass showed the increasing trend in the soil profile,while under the other three vegetation types it showed out the reversed S-shape;（2）in general,the soil water contents in the 0—500 cm soil profile under the natural grass and Pinus tabuliformis Carr.were more stable with smaller variation coefficients than that under the Hippophae rhamnoides L.and the mixed forest;for all the four vegetation types,the average soil water contents in spring and winter were significantly different with those in summer and autumn;soil water showed the accumulative effect in spring and winter and the depleting effect in summer and autumn;（3）rainfall had a significantly effect on soil water content in 0—200 cm soil profile,however,this effect tended to disappear in the 200—500 cm soil depth;it is various that vegetation types enhanced the discrepancy of soil water storage.The conclusions are as follows.Soil water content under the natural grassland was higher and less variable,while under shrub and arbor trees it was lower and more variable.The change of soil water content showed the coincident trend under precipitation input and temperature alteration along the soil profile and over the time,the effect of vegetation types signified the obvious response of soil water content to precipitation and temperature on the basis of consistency.