Study On Spatial Pattern Of Soil And Water Conservation Function In Loess Hilly Region

Understanding and mastering the spatial pattern of soil and water conservation can better serve the regional sustainable development and ecological environment construction of soil and water conservation.In this study,pengyang county,located in the loess hilly area,was selected as the research area,taking 1995-2015 as the research time scale,based on remote sensing data,DEM data,soil data,meteorological data,etc..With the support of ArcGIS,ENVI and MATLAB,the comprehensive utilization of 3S technology,the BPNN model,the RUSLE model,the In VEST model,the dimidiate pixel model,the trend significance analysis method,terrain area difference correction method and other methods,take vegetation restoration as the background,first of all,through exploring the most significant factors affecting soil erosion,and combined with the characteristics of vegetation cover change to explore the spatial pattern of vegetation restoration in pengyang county.Then the spatial distribution pattern of the two indexes of soil conservation function and water retention function were analyzed combining with the spatial distribution pattern of vegetation restoration.Finally,through the evaluation of soil conservation function and water retention function,the importance evaluation grade is divided,the data is standardized by using the fuzzy membership function,and the spatial pattern of soil and water conservation is comprehensively evaluated.The main conclusions are as follows:(1)Topography and soil are important factors affecting soil erosion.In terms of spatial scale,the topographic SL factor have the most significanct influnence on soil erosion,while the soil erodibility K factor have the weakest significance.On the time scale,the significance of rainfall erosive force R factor fluctuates with the change of rainfall.The significance of soil and water conservation measures P factor and vegetation cover and management C factor were related to the implementation of ecological construction projects.The prediction errors of BPNN are all less than 5%,which can effectively predict the significance of each influence factor on soil erosion.The overall significance of soil erosion factors is:SL>P>R>C>K.(2)From 1995 to 2015,vegetation in 76.99%of the study area was significantly improved,22.94%of the area was in a stable state,and 0.07%of the area was significantly degraded,all of which passed the significance test of 0.05.The vegetation growth pattern was in the range of 1900-2000 meters above sea level,and it showed a significant dominant distribution in the semi-negative slope and semi-positive slope areas with slope greater than 15°.The dominant distribution area of vegetation stability was higher than 2100 meters above sea level,and the dominant distribution was found in flat area with slope less than 2°.The vegetation reduction area is small,and the dominant distribution is simple,mainly distributed in the range of 1400-500 meters above sea level,and in the negative slope area with slope less than 6°.(3)The soil conservation quantity and water retention quantity in pengyang county show an obvious increasing trend.During the study period,soil retention amount in the study area was 133.86,176.51,223.59,255.23 and 269.12 t/(hm2·a),respectively.On the spatial scale,the soil retention amount presented a vegetation growing>vegetation stable>vegetation reduction,and when the vegetation change type was dominant at different elevations,slopes and aspects,the soil conservation amount of the growth type was mainly increased significantly,while the soil conservation amount of the stability type was mainly increased steadily and slowly.During the study period,the water retention capacity was 90.07,77.73,95.40,151.27 and 170.49 m3/(hm2·a),respectively.On the spatial scale,the quantity of water retention presents an increasing type ? stable type,and the reduction of vegetion is basically unchanged.When the vegetation change types had significant dominant distribution in different slopes and aspects,the water retention amount of the growth type was mainly increased slowly,while that of the stable type was mainly increased by fluctuation.When the dominant distribution is at different elevation levels,the water retention quantity of the growth type increases sharply,while that of the stable type decreases gradually.(4)The importance levels of soil conservation and water retention in pengyang county showed a trend that from general importance and more importance to highly important and very important regions.From 1995 to 2015,the area of soil conservation function in general important areas and more important areas decreased significantly,from the large area distribution in the county region to only distributed in the relatively flat terrain of the Honghe and Ruhe basin.However,the area of highly important and very important areas increased significantly,in 1995,it was only distributed in the Honghe,Ruhe basin and the Liupan mountain ecological protection area,and in 2015,it was distributed in the whole region.The water retention function of the study area is general important and the area of the more important areas is significantly reduced.From the large area distribution in 1995 to the northeast of pengyang county only in 2010 and 2015.The area of the highly important and very important areas increased significantly,which was only distributed in the Honghe,Ruhe basin and the Liupan mountain ecological protection area in 1995,and in 2015,it was distributed in a large area in the county,with the most significant changes in the south and northwest of the study area.(5)From 1995 to 2010,the soil and water conservation function of pengyang county was general important and more important,decreasing from 81.08%in 1995 to 48.70%in 2010.In 2015,it was mainly of medium importance,accounting for 44.15%of the total area of pengyang county.From 1995 to 2015,the area of the highly important and very important region increased from 1.70%in 1995 to 18.41%in 2015,and the distribution in the Honghe and Ruhe basin and Liupan mountain in 1995 gradually changed to the large area distribution in 2015,with the south and northwest of the study area being the most significant.