Agricultural land-use patterns and soil erosion vulnerability of watershed units in Vietnam’s northern highlands |
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| Authors: | Karine Vezina Ferdinand Bonn Cu Pham Van |
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| Institution: | (1) Remote Sensing Applications and Research Center (CARTEL), Sherbrooke University, 2500 University blvd., J1K 2R1 Quebec, Canada;(2) Center For Remote Sensing and Geomatics (VTGEO) Institute of Geology, Vietnamese Academy of Science and Technology, 340 Bach Dang Chuong Duong, Hoan Kiem, Hanoi, Vietnam |
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| Abstract: | Since the mid eighties, agricultural development and increased population growth in Vietnam’s northern highlands have modified
land use patterns and thus, increased the runoff process and soil degradation induced by water erosion. In the last decade,
Vietnamese literature has focused on the computation of soil losses over large areas. Most of these spatial and quantitative
soil erosion studies do not consider the impact of agricultural land use diversity (spatial heterogeneity), particularly at
the watershed scale, and the annual variability of seasonal landscape factors on soil erosion vulnerability and hence, landscape
dynamics. We present an integrated approach combining field measurements and observations, GIS and modeling to determine the
spatial and temporal dynamics of soil erosion vulnerability according to watershed units and hence, the impact of physical
environment components and agricultural land use patterns on landscape evolution. Tables and graphics showing the cropping
systems, the periods within a year, and the watershed units that are most vulnerable are presented. The double cultivation
cycles for paddy rice fields not only imply two periods of land preparation and establishment that expose the soil surface
to raindrop impacts, but also increased soil management practices that decrease the soil’s resistance to detachment. Despite
the low levels of soil management practices for the shifting cultivation system, the near absence of soil conservation practices
clearly increases their vulnerability. Hence, rainfed cropping systems, mainly soya and cassava, cultivated on sloping lands
(hills and mountains) where soil erosion vulnerability is the highest represent the watershed units which are the most prone
to soil loss. |
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| Keywords: | Tropical environment Watershed Erosion dynamics Scaling in space and time GIS |
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