Study On Land-use/cover Change And Soil Erosion In Datong County

Datong is located in the transition zone of Qing-Tibet Plateau and the Loess Plateau,a very important ecological area.Based on multi-source data as well as comprehensive academic comprising theoretics of landscape ecology and soil erosion,by using various method such as remote sensing and GIS technology and mathematical modeling,the paper studies the space-time characteristics of Land-use/cover change(LUCC) during the past 10-year from 1995 to 2005 and forecast the future trend of LUCC in Datong County;analyzes the trial data and observational data for the relationship between land-use/cover and soil erosion;builds soil erosion prediction model RUSLE in order to comprehensively evaluate soil erosion conditions of Datong County.The main conclusions are listed as follows:1,The characteristics of land-use/cover changes on quantitative structure:Woodland,water and construction land take on a growth trend,of which woodland becomes the largest land-use/cover types with the most significant increase in 2005.Woodland distributes mainly in the semi-hilly and semi-mountain,the hilly and unbroken mountain areas,showing the rise of various magnitudes in every town;Grassland,cultivated land and unused land display a decreasing trend,in which the grassland turn into the second from the advantage types of 1995,because of a remarkable reduction.Grassland of spatial distribution are basically the same as woodland,the majority towns have different decreases;In the most of town,cultivated land show a various degree of reduction,and mostly position valley areas of the Beichuan River and its tributaries on both sides.The mutual conversion between different land-use/cover type is strong,the area 186894.97hm~2,accounting for the total area of 60.18%;The transition of grassland to woodland,area of 68040.88hm~2,is the most amount accounting for the total change of 36.41%.2,The characteristics of land-use/cover changes on spatial pattern:The degree of landscape fragmentation and habitat isolation is falling because of the reduction in Patch density(PD),Largest patch index(LPI)and Edge density(ED);With the patch shape becoming simplistic,Area-weighted mean shape index(AWMSI) and Area-weighted mean patch fractal dimension(AWMPFD) is also reduced during the study period;Owing to the landscape being controlled by woodland,grassland and cultivated land,Contagion index(CONTAG) increase in the spread,although the advantage of patch gradually form a good connectivity and patch area tend to uniformity.The decrease of Shannon's diversity index(SHDI) and Shannon's evenness index(SHEI) indicates that decline in landscape heterogeneity, moreover reduce in the degree of fragmentation and landscape diversity. 3,The optimization sequencing of SQI on different land-use types is Picea crassifo1lia(0.80)＞Larix Principis～rupprechii(0.73)＞Hippophae rharnnoides ssp.sinensis(0.57)＞Medicago etiva(0.36)＞highland barley(0.31),which is the same as the soil anti-scourability indexes,and the two indexes is a significant positive correlation.4,The influence of land-use change on the rainfall-runoff relationship or runoff-sediment relations are more obvious,the growth rate of sediment transport in the period 1991-1995 is greater than 2001-2005;Under the same conditions of run-off,in the period 2001-2005 the sediment transport will be significantly reduced.There are many conversions from cultivated land and grassland into woodland in＞15°areas,so as to improve vegetation cover and rainfall interception capability,reduce the splash erosion of raindrops.5,Depend on soil erosion prediction model(RUSLE) and GIS technology to estimate the soil-erosion status in Datong County:Intensity soil-erosion belongs to Datong County with 2160.07×10~4t/.a of soil-erosion quantity and 51.83t/hm~2.a of soil erosion modulus in 2005.Cultivated land being acuity soil-erosion has the highest soil-erosion quantity in various land-use types,while its soil erosion modulus gets 199.97t/hm~2.a;the areas of intensity soil-erosion distribute mainly in the elevations of 2500-2700m and 2700-2900m,the steep slopes of 15-25°and 25-35°,as well as the southern aspect;moreover,these regions are intensive to prevent soil-erosion.And by contrast with 1995-yaer,the soil-erosion status is improving gradually with the reduction of 778.1×10~4t on soil-erosion quantity.