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Dynamic monitoring of soil erosion in the upper Minjiang catchment using an improved soil loss equation based on remote sensing and geographic information system

Guo, Bing, Yang, Guang, Zhang, Feifei, Han, Fang, Liu, Chenggang
Land degradation & development 2018 v.29 no.3 pp. 521-533
ecosystems, equations, forests, geographic information systems, grasslands, landscapes, monitoring, mountains, planning, remote sensing, soil, soil erosion, topography, water conservation, watersheds, China
The upper Minjiang catchment has suffered intensive soil erosion due to frequent geologic hazards and its fragile ecosystem zone with steep slopes. This study fully considers the topographic features and surface cover and introduces improved methods of K, LS, and C to establish a soil loss equation for the upper Minjiang catchment based on remote sensing and geographic information system. Spatial–temporal change patterns of soil erosion intensity and its driving mechanisms are then analyzed and discussed. Results show that (a) the soil erosion modulus of the upper Minjiang catchment for 2005 and 2015 were 1,577.29 t km⁻² a⁻¹ and 1,619.77 t km⁻² a⁻¹, both of which belong to a level of mild erosion. The slight and mild erosion zones covered the largest area and were widely distributed in the northern part of the study area, whereas zones of intensive and severe erosion were mostly concentrated in Wenchuan County and the lower reaches of the Heishui and Zagunao Rivers. (b) During 2005–2015, changes in erosion intensity showed a trend of “overall stability, local deterioration.” Zones of mild, moderate, and intensive increase were mainly concentrated in the Longmen Mountain Fault Zone, such as southern Maoxian and western Wenchuan Counties. (c) Returning cultivated land to forest and grasslands greatly reduced the erosion intensity and erosion amount, whereas geologic hazards aggravated the soil erosion condition. Zones with a slope of <35° had a positive relationship with soil erosion intensity; these areas are crucial control areas for soil preservation and containing soil loss. In addition, grassland is more effective in conserving soil and water than forestland in the upper Minjiang catchment in areas of steep terrain. These results provide an important reference for estimating soil loss intensity in southwest mountainous regions of China, particularly in the Hengduan Mountains, and greatly contribute to the planning of soil and water conservation.