砒砂岩黄土区植被盖度对土壤侵蚀的影响

十大孔兑砒砂岩区为鄂尔多斯北部水土流失最为严重的地区之一,土壤侵蚀发生、发展极大影响了区域水、土资源开发利用。应用通用土壤侵蚀模型(Universal Soil Loss Equation, USLE)计算了区域土壤侵蚀模数,采用整体回归拟合和分段回归拟合的方法对研究区植被盖度和土壤侵蚀模数的关系进行了分析并识别土壤侵蚀模数阈值和对应植被盖度。结果表明:2000—2017年十大孔兑砒砂岩黄土区土壤侵蚀模数在时间尺度上呈现复杂的变化趋势,多年土壤侵蚀模数平均值为29.31 t hm~(-2) a~(-1);最大和最小值分别为65.6 t hm~(-2) a~(-1)和10.95 t hm~(-2) a~(-1)。从总体来看,土壤侵蚀模数随着植被盖度增加呈极显著抛物线型变化趋势(P0.001);在坡度级别分别为5°、5—10°和10°时,土壤侵蚀模数阈值(18.18 t hm~(-2) a~(-1)、34.29 t hm~(-2) a~(-1)和74.56 t hm~(-2) a~(-1))对应植被盖度分别为11.42%、16.51%和16.5%。结果解释了砒砂岩黄土区土壤侵蚀模数不仅受到了USLE模型中诸因子的影响,而且也受到了土壤可侵蚀量限制。此外,判断区域土壤侵蚀与植被盖度关系时应高度关注较大侵蚀量年份。

The influence of vegetation coverage on soil erosion in sandstone loess area

Soil erosion is one of the most serious soil degradation problems in the world. Its abnormally occurrence, development and change process directly affect the development and utilization of water and soil resources. Meanwhile, it threatens human survival, social and economic development. Numerous studies have shown that the increased vegetation coverage was a main factor to reduce soil erosion. It was an important issue attracted much attention of researchers in soil and water conservation that the quantitative relationship between vegetation coverage and soil erosion in different research areas in the world. Ten Turbutries located in northern Ordos is one of the most serious soil erosion areas, which was mainly distributed by moderate and severe erosion area, and covered by sandstone loess. In our study, the soil erosion modulus was calculated using Universal Soil Loss Equation (USLE) based on remote sensing technique, rainfall, DEM and land use/cover data. Then, the relationship between vegetation coverage and soil erosion modulus was analyzed by the method of overall fitting and sectional fitting regression to identify the vegetation coverage corresponding to the threshold of soil erosion modulus. The results showed that the annual average soil erosion modulus was 29.31 t hm^-2a^-1 from 2000 to 2017. The largest in 2016 and the smallest in 2011 were 65.6 t hm^-2a^-1 and 10.95 t hm^-2a^-1, respectively. The change trend of soil erosion modulus was a typical parabolic curve (P<0.001). When the slope grades were <5°, 5-10°, and > 10°, the threshold of soil erosion modulus were18.18 t hm^-2a^-1, 34.29 t hm^-2a^-1 and 74.56 t hm^-2a^-1, and the corresponding vegetation coverage were 11.42%, 16.51% and 16.5%, respectively. In the sandstone loess area, the soil erosion modulus not only would be affected by the factors in USLE model, but also limited by the amount of soil erodibility. In addition, it should be paid great attention to the years with large amount of erosion when judging the relationship between soil erosion and vegetation coverage in regional scale.