Study On Land Use Change Characteristics In Ning'an City Based On The Terrain Gradient

Mountain and hilly area is a complex natural system dominated by terrain factors.The land use change caused by the combination of various factors has a profound impact on people's life and mode of production.Therefore,analyzing the characteristics and rules of land use types in time series,spatial distribution and overall dynamic change is of great significance for defining the constraints and differences of terrain elements on the change of regional land use types.Based on the topographic factors and the relationship between land use change as the starting point,select the typical cold mountain and forestry ecotone--Ning'an city in Heilongjiang Province as the study area,using the TM remote sensing images in 1999,2007 and 2016 as the original data,obtaining land use data of three phase in RS and GIS platform;With the help of DEM data extraction of slope and elevation data,the terrain index,distribution index model to analyze the distribution characteristics of land use types and variation in different terrain gradient classes,and describes the study area of land use change in quantity,type transformation and dynamic degree of three aspects of the overall characteristics,at the end of the type the study area of land use change in the long-term forecast.The results of the study show that:(1)The selectivity of the forestland and grassland to the elevation gradient was the least,and it was widely distributed from 300~1100m;The water and construction land have the highest selectivity and small distribution range for the elevation gradient,and the gradient effect is very obvious.The distribution of cultivated land in 300m~500m is the most,and the unused land is mainly concentrated in the area within the elevation of 700 m.The forestland is the best ground for the slope suitability in all kinds of land.The unused land and the water area are mainly distributed in the low lying area of 0~4 degree or the gentle slope of the slope;The construction land is rarely distributed in more than 16 degrees;The cultivated land is concentrated in the range of 0~8 degree.The dominant topography of cultivated land and woodland is the most extensive,and the dominant terrain of grassland and construction land is the smallest.(2)On the first gradient of elevation,the area of cultivated land shows a small steady growth trend,and the area of the construction land is generally stable;Second,the most violent land class is grassland and unused land.On the third gradient,the area change of cultivated land,forest land and construction land first decreases and then increases,but the unused land increases continuously,and the grassland increases first and then decreases;On the fourth gradient,the area of cultivated land was suddenly reduced;The area of fifth gradient and sixth gradient is only woodland and grassland,and the area change is small.The changes in the grade of gradient grade are as follows: the change trend of cultivated land and woodland area is consistent,and then decreases and then increases;The area of water and construction land belong to steady and steady growth;The area of the grassland and the unused land increased first and then decreased.From the inter-annual variation of the topographic distribution index,the four types of farmland,woodland,construction land and water area have little difference;The main variation in the distribution index of the grassland and unused land was in the highland shape.(3)From the quantitative point of view,the study period of Ning'an city cultivated land and woodland are decreased first and then increased,but the total area of cultivated land change in small;The area increment of grassland and unused land was very obvious in 1999-2007 years,and it fell again in 2016;The total area of unused land was narrowed in 2016,which was the lowest in area.From the point of view of land transfer,the total amount of cultivated land is basically flat.The area of woodland and grassland has been expanded.From the point of view of land class dynamics,the biggest difference of dynamic changes is the gradient grades of 500~700m,>1100m,less than 4 degrees,and greater than 22 degrees.(4)In 2023-2039 years,the number of cultivated land and woodland decreased slightly.After 2031,the number of grassland increased,the number of water and construction land increased steadily.The number of unused land increased slowly.Through principal component analysis,the main factors driving changes in Ning'an city land use is the drive of social and economic factors,reflected in promoting rapid economic growth and the improvement of living standards,the expansion of the population and policy.