黄土丘陵沟壑区陡坡微地形分布研究

水分是黄土丘陵沟壑区植被建设的主要限制因素，而陡坡的水分条件差，导致坡面上水分空间差异的微地形成为陡坡坡面植被恢复的关键因素。利用三维激光扫描全站仪实测陕西省吴起县合家沟流域的地形参数，以Arc GIS 9.2为平台，对切沟、浅沟、缓台、塌陷和陡坎5种微地形在陡坡坡面的分布情况进行了研究。结果表明：陡坡坡面微地形占坡面面积比例介于18%～30%，平均为23.13%；各类微地形占坡面面积比例平均值从大到小依次为切沟8.44%、缓台6.66%、浅沟5.00%、陡坎1.53%、塌陷1.52%；坡面坡向和坡面坡度是影响浅沟、切沟和塌陷占坡面面积比例的主要地形要素，陡坎占坡面面积比例主要受坡面坡度的影响，而坡面坡向与坡面坡度对缓台占坡面面积比例均没有明显的影响；不同坡向陡坡微地形占坡面面积比例大小顺序为：阳坡＞半阳坡＞半阴坡＞阴坡，塌陷、浅沟和切沟占坡面面积比例为阳坡和半阳坡大于半阴坡和阴坡；陡坎、浅沟和切沟占坡面面积比例随着坡度的增大而减小、塌陷占坡面面积比例随着坡度的增大而增大。

Study on Distribution of Microrelieves on Steep Slopes in a Loess Hilly-gully Region

Soil moisture content is the main factor affecting vegetation conservation and regeneration in the loess hilly gully region, but it is low in steep slope. Microrelief affects strongly the soil moisture content in slope. A field measurement of the terrain parameters was carried out with a 3 dimentional laser scanning total station in the Hejia Valley in Wuqi County, Shaanxi Province. The distribution of gullies, shallow gullies, platforms, scarps and collapses on steep slope was researched based upon Arc GIS 9.2. The results showed that the proportions of area of microrelieves varied in a range of 18%-30% of the total steep slope area and 23.13% in average. The proportions of area of different microrelieves were in an order of gully (8.44%)>platform (6.66%)>shallow gully (5.00%)>scarp (1.53%)>collapse (1.52%). Exposure and slope were the main topographic factors affecting the proportions of area of gullies, shallow gullies and collapses, the proportion of area of scarp was mainly affected by slope, and there was no obvious effect of exposure and slope on the proportion of area of gentle platform. Exposure affected the proportions of area of microrelieves on steep slope, proportions of the microrelieves were in an order of sunny slope ＞semi sunny slope＞semi shaded slope＞shaded slope, and the proportions of area of collapse, gully and shallow gully on sunny slope and semi sunny slope were higher than those on semi shaded slope and shaded slope, however, there was an opposite result for the proportion of area of scarp. The proportions of area of scarp, gully and shallow gully were decreased with the increase of slope, but the proportion of area of collapse was increased with the increase of slope.