基于RUSLE-SMA的黄土丘陵沟壑区土壤侵蚀评价及景观格局分析——以庆城县蔡家庙流域为例

Soil erosion evaluation and landscape pattern analysis of loess hilly gully area based on RUSLE-SMA:A case study of Caijiamiao watershed in Qingcheng,Gansu Province of Northwest China

以甘肃省庆城县蔡家庙小流域为例,运用混合光谱线性分解(SMA)从Landsat遥感影像提取植被覆盖度,获取流域的植被覆盖因子,借助通用土壤侵蚀方程RUSLE计算了2003和2010年土壤侵蚀量,分析了土壤侵蚀与土地利用和地形因子之间的关系,并对流域土壤侵蚀景观格局变化进行了研究。结果表明:7年间,蔡家庙小流域土壤侵蚀量由3.61×106t·a-1增加到4.48×106t·a-1,增加了24%;平均侵蚀强度由8590.23t·km-2增加到10652.01t·km-2。不同土地利用类型的侵蚀状况差异较大,未利用地、草地、园地的侵蚀状况严重;坡度大于15°、高程低于1395m以及坡向朝西的区域,土壤侵蚀较严重。研究区整体侵蚀景观高度破碎,斑块总数减少,破碎度变小,景观异质性减小,整体形状趋于规则;除微度侵蚀景观外,其余景观类型趋于简单化。

By using a linear spectral mixture analysis （SMA） model, the vegetation coverage in the Caijiamiao watershed in Qingcheng County of Gansu was extracted from the Landsat TM ima- ges, and the factors affecting the vegetation coverage were obtained. With the help of the revised universal soil loss equation （ RUSLE ） , the amount of the soil erosion in the watershed in 2003 and 2010 was estimated. The relationships between the soil erosion and the land-use type and topographic factors were analyzed, and the changes in the soil erosion landscape pattern were studied. In the 7 years from 2003 to 2010, the soil erosion amount in the watershed increased from 3.61~106 to 4.48x106 t ~ a-i, with an increment of 24%. The mean annual soil erosion intensity increased from 8590.23 t ~km-2 to 10652.01 t ~ km-2. The soil erosion varied greatly with land use type, being more serious on unutilized land, grassland, and garden land, and on the areas with a slope greater than 15~, elevation below 1395 m, and aspect west. Overall, the erosion landscape in the study area was highly fragmented, the total number of patches reduced, fragmentation degree lowered, landscape heterogeneity decreased, and landscape shape tended to be regular. Except the slightly eroded landscapes, the landscape types tended to be simplified.