黄土丘陵小流域土壤侵蚀的时空变异及其影响因子

Spatiotemporal variability of the soil erosion and its relations to the influencing factors on the Loess Plateau, China

采用土壤侵蚀模型 L ISEM(L imburg Soil Erosion Model)模拟黄土丘陵沟壑区大南沟小流域 5种土地利用格局下立地尺度上土壤侵蚀量的空间分布 ,从土壤侵蚀量与环境因子的关系分析入手 ,研究黄土丘陵小流域立地尺度上土壤侵蚀的时空变异性及其影响因子。研究结果表明 ,立地尺度上平均土壤侵蚀强度以 1975年 >1998年 >退耕格局 ,可见优化土地利用格局 (陡坡农地退耕 )可以有效地降低立地尺度上的土壤侵蚀强度。各种土地利用方案下土壤侵蚀强度的空间变异都很显著 ,相对来说以1975年 <1998年 <退耕格局 ,可见优化土地利用格局可以提高土壤侵蚀的空间变异性 ,降低土壤侵蚀危险的空间聚集度。土壤侵蚀量与降雨呈现显著正相关性 ,相关性以 L U 75 >L U 98>退耕格局 ,可见合理的土地利用格局可以有效地削弱降雨对土壤侵蚀强度的影响。土地利用方式对土壤侵蚀空间分布具有显著影响。从 1975年、1998年到 3种退耕格局 ,陡坡农地退耕还林还草 ,植被覆盖度增加 ,林地 /灌木地、果园 /经济林地、农地和休闲地的平均土壤侵蚀强度都逐渐降低。相关分析表明 ,林地 /灌木地上土壤侵蚀量最小 ,荒草地相对最严重 ;果园、休闲地和农地居中。土壤侵蚀强度还存在显著的地形分异。水平凹凸度和相对海拔对土壤侵蚀空间分布的影?

Based on the soil erosion modeling for five land use scenarios consisting of the previous in 1975 (LU75), present in 1998 (LU98), and future land use pattern (i.e. steep-slope-limit, FA) in which cropland areas are restricted slope gradients smaller than 25 (FA25), 20 (FA20) and 15 degree (FA15) using LISEM (Limburg Soil Erosion Model), the degree of spatiaotemporal variability of the soil erosion and the ability of environmental attributes to predict that spatial variability were studied in Da Nangou catchment (3.5km2) on the Loess Plateau, China. It is indicated that the mean soil erosion is the most significant for land use in 1975, moderate for land use in 1998 and weakest for three steep-slope-limit, which demonstrates that improvement of the land use pattern could lead to declining in soil erosion at site scale. The spatial variability in soil erosion is very significant, however, it shows the following rank for different land use scenarios: LU75<LU98<FA. This indicates that spatial variation in soil erosion increases with optimization of land use pattern, and so the spatial aggregation in soil erosion risk declines significantly, too. It is found that the soil erosion increases with increasing of precipitation and rainfall intensity, however the correlation between soil erosion and rainfall is most significant for LU75, moderate for LU98 and lowest for the three steep-slope-limit scenarios, which shows that appropriate land use pattern can reduce the influence of rainfall upon the soil erosion significantly. It is indicated that landuse also provides significant influences on the spatial distribution of soil erosion. From LU75, through LU98 to FA, the cropland on the steep slope was replaced by the wasteland or woodland/shrubland gradually, with increasing vegetation coverage, the mean soil erosion on the woodland/shrubland, orchard/cashing-tree land, cropland and following land decrease too. It is demonstrated that the soil erosion shows the lowest values on the woodland/shrubland, while its exhibits the highest values on the wasteland. The soil erosion also shows significant spatial variation in relation to topography, in which plan curvature and relative elevation exhibit a more significant influences on the spatial distribution of soil erosion than the aspect, slope and profile curvature do. It is found that the soil erosion exhibits a higher value on south-toward slope than north-toward slope, plan-convex slope than plan-concave slope, profile concave slope than profile convex slope, and it increases with decreasing elevation. For the land use in 1975 and 1998, the soil erosion is more significant on west-toward slope than east-toward slope, steep slope than flat slope, while for the three degree-limit scenarios the soil erosion demonstrates an opposite trend. This indicated that the appropriate land use pattern (steep-slope-limit scenarios) could significantly reduce the influence of topography upon the soil erosion.