Spatial-temporal Changes And Quality Evaluation Of Sloping Farmland Resources In Enshi City

As an important resource of agricultural production,the quantity and quality of cultivated land are directly related to the development potential of the national economy.Sloping farmland occupies a large proportion of cultivated land resources in China and is an influential force in agricultural modernization.In recent years,there are ecological and environmental problems such as soil erosion and quality decline in the development and utilization of sloping farmland in China.The construction of soil erosion model and the exploration of mechanism are the popular content in the study of sloping farmland.However,there are few studies on the spatial and temporal pattern and quality evaluation of sloping farmland,which are mainly concentrated in a few southwestern provinces.The quality and distribution pattern of sloping farmland in most areas are not clear yet.Enshi City is situated in the southwest area of Hubei Province.As the most important cultivated land resources in this area,it is of enormous significance for the development of agricultural production and regional economic construction to master its quantity change and quality distribution.Based on multi-period land use data,this study used GIS spatial analysis technology,combined with quantitative analysis methods such as land use transfer matrix and gravity center model,and took townships as the basic unit to explore the spatial and temporal distribution and dynamic evolution of sloping farmland resources in Enshi City in the past 20 years.DPSIR model and statistical yearbook data were used to identify its main driving factors.Soil data were collected through field sampling and household survey,and the evaluation index system was screened and constructed to comprehensively evaluate the quality of sloping farmland in Enshi City in 2020.The obstacle degree model was introduced to diagnose the principal obstacle factors of each township and put forward targeted quality improvement suggestions.The main conclusions are as following:(1)Spatio-temporal evolution pattern of sloping farmland and identification of its dominant driving forces: In 2020,there was a total sloping farmland area of 36426.06 hm~2 in Enshi City,accounting for 72.23% of the total cultivated land.The spatial distribution of sloping farmland showed obvious fragmentation characteristics,the sloping farmland area and average slope size varied greatly among towns.In the past 20 years,the area of sloping farmland in Enshi City has been fluctuating,showing an overall trend of "increase–decrease–increase".Compared with 2000,the area of sloping farmland in 2020 decreased by 21.87 hm~2,with a decrease of about 0.6‰.There has been frequent type conversion between sloping farmland and land use types such as woodland and grassland,but the area of transfer-in and transfer-out was generally flat,and the land use pattern remained basically stable.However,the spatial distribution center of sloping farmland has undergone obvious directional migration,showing a trend of moving from southwest to northeast.The direction,distance and speed of migration in each period are not completely consistent,and there are obvious differences,economic factors are the main factors affecting the spatio-temporal evolution pattern of sloping farmland,and agricultural factors play an important role.(2)Quality evaluation and grade spatial distribution characteristics of sloping farmland: The comprehensive quality index of sloping farmland in Enshi city is in the range of 0.55～0.90,which can be divided into ten grades,and the distribution of sloping farmland of each quality grade is uneven.In terms of quantity,among the ten grades of sloping farmland,the seventh grade has the largest distribution area,reaching 12187.80hm~2,accounting for 20.38% of the total area,while the tenth grade has the smallest distribution area,accounting for only 0.71% of the total area of sloping farmland.The quality of slope farmland is generally low.From the perspective of spatial distribution,the first grade,the second grade and the third grade are scattered in the middle of the study area,while the seventh grade,the eighth grade and the ninth grade are concentrated in the north,northwest and northeast of the study area.From the perspective of township units,the first grade,the second grade and the third grade are mainly distributed in Bajiao Township,Xintang Township and Baiyangping Town,while the eighth grade,the ninth grade and the tenth grade are mainly distributed in Tunbao Township and Cuiba Town.(3)Obstacle factors of sloping farmland quality and suggestions for quality improvement: Topographic location,irrigation capacity,farmland forest network degree,and available potassium are the main obstacle factors for the quality improvement of sloping farmland in the region,but except for topographic location,most indicators are in mild and moderate obstacle levels.The spatial distribution of each index obstacle degree level is not uniform,and there are obvious regional differences.According to the identification results of the main obstacle factors in each township,some targeted quality improvement suggestions such as improving the irrigation capacity and increasing the content of available potassium in the soil are put forward.