Spatiotemporal Variations And The Driver In Land Use/cover Change Based On Topography Gradient On The Loess Plateau

Land use/cover change(LUCC)is a key component of global climate change,and it has great impacts on climate,hydrological processes,biodiversity and ecological processes.Therefore,more attentions have been paid to land use/cover.As land use/cover pattern is significantly influenced by topographical factors that indirectly has impacts on water and surface energy balance,analysis of land use/cover pattern is thus a useful method to assess the changing process of land use/cover according to the variations in their topographic factors,which will further provide important information for vegetation management and soil conservation.The Loess Plateau is one of the regions with most severe soil loss,and it has been experiencing great changes in land use/cover pattern due to the implementation of soil conservation measures.Therefore,the land use type change,Normalized Difference Vegetation Index(NDVI),landscape index,which served as an evaluation index of LUCC,were used in this paper to detect and analyze the spatial and temporal variation of LUCC on the Loess Plateau and its 9 basins from 1982 to 2015.As soil erosion is closely related to topography,the relationship between elevation,slope,terrain niche,and vegetation cover change was examined to assess the effectiveness of LUCC.Finally,combined with the climate and economic factors,this paper systematically analyzed reasons of LUCC from the perspective of both qualitative and quantitative.The result showed that:(1)The main direction of LUC during 1986–2010 was decrease in farmland and unused land as well as increase in construction land and forest.The whole study period of 1986–2010 had the smallest values while the sub-period of 1995–2005 had the greatest values for the change magnitude,speed and types,which implied that the present land use structure was returning to the original one and the Grain for Green project accelerated LUC significantly.The regions occurring LUC appeared to be higher and steeper,and these changes altered the spatial distribution of each land use type.The land use patterns on CLP during 1986–2010 were becoming more rational.(2)From 1982 to 2015,the vegetation in the study area showed an increased trend,and the speed of 2000–2015 was significantly higher than 1982–1999.The main NDVI grades for different regions have a certain difference.But their changed trends in magnitude were relatively consistent,which behaved that low-grade NDVI areas were reducing while high-grade NDVI areas were increasing.And the changed range of 2000–2015 was higher than 1982–1999.In topography,the low-grade NDVI tended to move the higher and flatter regions,while the high-grade moved to the lower and flatter regions.(3)This paper analyzed the characteristics of Land Use and Landscape Pattern in the Loess Plateau.The landscape dominance and cohesion of the Loess Plateau decreased,the landscape fragmentation and the landscape heterogeneity increased,and the patches were evenly distributed in the space.There are differences in the landscape pattern of land use in different watersheds,mainly due to the decrease of the degree of fragmentation of Tuwei River and Kuye River,and the degree of fragmentation of Weihe River Basin.The variation pattern of different landscape patterns is obvious.Grassland,farmland and woodland are the dominant plaque types in the study area.The degree of fragmentation is low,and the dominance of cultivated land is weakened for many years,and the forest land is enhanced and the grassland is not changed greatly.The landscape dominance of construction land was enhanced,the degree of patch fragmentation was weakened,and tends to be clustered,while the waters and unused land are not dominant in the study area.(4)Explores the reasons for the change of landscape pattern of land use in the Loess Plateau.The change of land use pattern is mainly affected by natural factors and human activities.The influence of each factors is obvious difference in different time periods and regions.From 1982 to 1999,the climate have played a major role in vegetation cover change,and the change of vegetation coverage dominated by human activities in 2000–2015,the dominant factor driving the change of landscape pattern of modern land use was human activity.Climate change have played a major role in LUC in the CLP,but the process is accelerated by human activities in a short time period.