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Extent of Cropland and Related Soil Erosion Risk in Rwanda (卢旺达农田面积扩张带来的土壤侵蚀风险研究)
Fidele Karamage
Thesis Advisor张驰(Chi Zhang)
Degree Grantor中国科学院大学
Place of Conferral新疆乌鲁木齐
Degree Discipline理学硕士
Keyword水土流失 农田 梯田 Rusle 遥感 Soil Erosion Cropland Terracing Rusle Remote Sensing
Abstract在非洲,农田开垦是造成土壤侵蚀的主要原因。本研究以卢旺达为例,评估了该国当前的农田面积和土壤侵蚀情况。卢旺达是非洲最近十年人口增加和农田扩张最快的国家。我们利用 Landsat-8 影像,得到了卢旺达 2015 年的土地利用和覆被数据。基于降水、土壤性质、数字高程模型(DEM)、归一化植被指数(NDVI)和土壤保护因子数据,驱动 RUSLE(Revised Universal Soil Loss Equation)模型,评估了卢旺达的土壤侵蚀速率,空间分辨率是 30 米。模型结果显示,该国坡地的平均土壤侵蚀速率是 13.64 t ha-1y-1,每年土壤总流失量约为三千万吨。农田占总侵蚀面积的 60%,速率为 12.62 t·ha−1·y−1,占总流失量的 56%。约 93.49%的农田,其平均土壤流失率超过 1 t·ha−1·y−1。同时,土壤侵蚀率高(>10 t·ha−1·y−1)的农田有 42.94%位于坡度大(27-50%)和降水强(1119-1254 mm y-1)的地区。根据我们的研究,仅建造梯田就可以使土壤流失率减少 70%。控制火灾和减少人为干扰,如控制乱砍乱伐和牲畜的踩踏,可以减少森林和草地的土壤侵蚀风险。土壤侵蚀的减少能改善卢旺达的水体污染和粮食安全问题。该研究使用的方法可以帮助其他科学家和土地管理者评估实测数据缺乏地区的土壤侵蚀情况,指导人们采取合理的保护措施治理土壤。
Other AbstractLand conversion to cropland is one of the major causes of severe soil erosion in Africa. This study assessed the current cropland extent and the related soil erosion risk in Rwanda, a country that experienced the most rapid population growth and cropland expansion in Africa over the last decade. The land use and land cover (LULC) map of Rwanda in 2015 was developed using the Landsat-8 images. Based on the precipitation, soil properties, Digital Elevation Model (DEM), Normalized Difference Vegetation Index (NDVI) datasets, and the conservation support practice factor, the soil erosion rate of Rwanda was assessed at 30-m spatial resolution, using the Revised Universal Soil Loss Equation (RUSLE) model. According to the results, the mean soil erosion risk rate was 13.64 t·ha−1·y−1 over the erosion-prone lands of the country, with a total soil loss of approximately 30 million tons per year. The mean soil erosion rate over the cropland, which occupied 60% of the national erosion prone area, was estimated at 12.62 t·ha−1·y−1 and was responsible for about 56% of the total national soil loss. About 93.49% of the cropland comprised an unsustainable mean soil loss rate >1 t·ha−1·y−1. While 42.94% of the croplands that had high soil loss rates >10 t·ha−1·y−1 was located on very steep slopes ranging from 27% to 50% and high rainfall intensity ranging from 1,119 to 1,254 mm·y−1. According to our assessment, terracing alone could reduce the mean rate of cropland soil erosion by 75%. The control of soil erosion risk from the forests and grasslands would be achieved through the control of wildfires, and human-induced disturbances such as uncontrolled timber harvesting and soil compaction from livestock that would increase the risk of soil erosion likelihood. Soil erosion reduction could reduce the problem of water pollution and food insecurity in Rwanda. Further scientific contribution includes the methodology used in this study that can help other scientists and land managers to assess soil erosion risk in the regions with scarce data, guide in soil erosion control and making a good decision throughout the selection of suitable conservation support practice.
Subject Area地图学与地理信息系统
Document Type学位论文
Recommended Citation
GB/T 7714
Fidele Karamage. Extent of Cropland and Related Soil Erosion Risk in Rwanda (卢旺达农田面积扩张带来的土壤侵蚀风险研究)[D]. 新疆乌鲁木齐. 中国科学院大学,2017.
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