黄土丘陵小流域地形和土地利用对土壤水分时空格局的影响

采用1982～1985年和2002年两个时段的定点观测数据,系统分析了小流域尺度地形和土地利用类型对土壤水分时空格局的影响.结果表明:1)土壤水分变化特征为所有年份农地土壤水分都最大,灌木林地和荒草地较低,林地居中;不同坡向间以阴坡土壤水分最大;而不同坡位间以坡中部土壤水分最大.受降雨和植被耗水的影响,所有土地利用类型中土壤水分在整个生长期表现为降低型.2)在年尺度上表现为干旱年份土地利用类型和坡向对土壤水分的影响较大;而在湿润年份,其影响程度减弱;坡位在干旱和湿润年份对土壤水分的影响都较小.湿润年份,降雨量的增大弱化了地形和土地利用类型对土壤水分时空格局的影响;而干旱年份正好相反.3)在季节尺度上表现为在生长季节的中后期,土壤水分的变异格局主要受坡向影响;而在生长季节的中期,主要受土地利用类型影响;坡位在整个观测时段内影响都较小.4)在不同土壤层次方面特征为土地利用类型对0～20em层次影响较小,而对其他4个深度较大的层次(20～100cm)影响较大,并且5个层次中以40～60cm层次的差异最大;坡向对5个层次土壤水分的变异格局均有明显影响,并呈现随着深度的增加,其影响减弱的趋势;坡位对5个层次的土壤水分变异格局影响均较小.

THE INFLUENCE OF TOPOGRAPHY LAND USE ON SOIL MOISTURE SPATIAL-TEMPORAL PATTERN IN THE HILLY AREA OF LOESS PLATEAU

Based on fixed and consecutive sampling of soil moisture in hilly area of Loess Plateau,the influence of topography and land use on the spatial -temporal pattern of soil moisture were analyzed. The results are as follows:1) soil moisture of cropland is highest among the four land use types. Soil moisture of woodland is the second. Soil moisture of shrubland and wasteland are the lowest among the four land use types. Slope aspect of N170° has the highest soil moisture among the three slope aspects. Middle part of the slope has the highest soil moisture among the three slope positions. The soil moisture of all land use types behaves decreasing type in the whole. It is influenced by the rainfall characteristic and growth of vegetation. 2) land use types and slope aspect have significant influence on soil moisture except for wet years. Slope position has slight influence on the variability pattern of soil moisture in wet and dry years. 3) land use types have significant influence on soil moisture variability in middle period of growth. But slope aspect has significant influence on late period of growth. 4) land use types have significant influence on soil moisture with soil of 20～100cm depth, but not with 0～20cm. The soil of 40～60cm layer has the greatest difference among the 5 layers. Slope aspect has significant influence on soil moisture with soil of 0～100cm depth, and its influence decreases with depth increasing. Slope position has slight influence on the variability of soil moisture of the 5 layers.