黄土高原六道沟流域不同土地利用方式下土壤水力特性及其对土壤水分的影响

Soil hydraulic properties and their influences on soil water content under different land uses in Liudaogou watershed of Loess Plateau

采用地统计学中交互相关系数方法,对黄土高原六道沟流域农田、荒草地、林地、苜蓿地4种土地类型土壤剖面水力特性及其对水分分布的影响进行了分析.结果表明:研究区农田与荒草地的土壤特性相似,苜蓿地与林地相似;相同吸力条件下,土壤水分以农田最大、林地最小,而饱和导水率则相反;除土壤水分消耗期的林地和苜蓿地土壤水分随土层深度增加呈上升趋势外,其他时期各土地利用方式下土壤水分均随土层深度的增加而降低.土壤剖面饱和导水率与土壤含水量之间的影响程度依土壤水分条件而异:水分补偿期,剖面土壤饱和导水率对滞后其空间距离0～40cm土层内的土壤含水量具有显著影响,而土壤水分含量对饱和导水率的影响范围为0～50cm;水分稳定期,饱和导水率与土壤含水量的相互影响范围均在0～60cm;水分补偿期和稳定期,二者之间为正相关;土壤水分消耗期,农田和荒草地饱和导水率与水分含量呈正相关,饱和导水率对土壤水分含量的影响范围在滞后其空间范围0～80cm土层内,而土壤水分含量对饱和导水率的影响范围在0～60cm内,林地和苜蓿地则呈负相关,相互影响范围均在0～60cm土层内.

By the method of cross correlation coefficient in geo-statistics, this paper studied the soil hydraulic properties and their influences on soil water distribution under four land uses, i. e. , farmland, waste-grassland, forestland, and alfalfa land in Liudaogou watershed of Loess Plateau. The results showed that farmland soil and waste-grassland soil had the similar physical characteristics, as did forestland soil and alfalfa land soil. For any given soil suction, farmland soil had the highest water content, while forestland soil had the lowest one. The opposite was observed for the saturated hydraulic conductivity of soil water. In forestland and alfalfa land, soil water content increased with increasing depth during water consumption period, but decreased with soil depth at any other time. The influence range of saturated hydraulic conductivity on soil water content depended on soil water condition. During the compensation period of soil water, the influenced lag distance of saturated hydraulic conductivity to water content was 0-40 era, and that of water content to saturated hydraulic conductivity was 0-50 cm; while during the stable period of soil water, the influenced lag distances of saturated hydraulic conductivity and water content were both 0-60 cm. There were positive correlations between the two properties under all land uses during these two periods. During water consumption period, saturated hydraulic conductivity was positively correlated with soil water content in farmland and waste-grassland. The influence range of saturated hydraulic conductivity to water content was about 0-80 cm, while that of water content to saturated hydraulic conductivity was 0-60 cm. However, negative correlation was observed in forestland and alfalfa land, and the influence ranges were also about 0-60 cm.