Cultivated Land Quality Evaluation Based On Remote Sensing And SVM Model Of South Songnen Plain

Arable land is one of the important land resources supporting social and economic development and an important guarantee for human food and ecological security.As China’s urbanization process is accelerated,arable land decrease and arable land quality decline become more serious a serious which have threaten to the food security and ecological environment.Combining with remote sensing and measured data,comprehensively evaluate arable land quality has an important significance for understanding how the arable land changes in quantity and quality and ensuring the total arable land productivity.Songnen plain is China’s major grain producing areas and important commodity grain production base.After 2000 year,as a result of the national policy guidance,local government implemented a significant land consolidation project,and amount of arable land and conversions between arable land and other land cover types have occurred,which produced a significant impact on the quality of arable land.Based on the soil measured data,image data of Landsat TM/ETM+/OLI images and MODIS dataset,this paper used the method of Support vector machine data together with GIS to evaluate the arable land quality in the South of Songnen Plain.First,based on the spatial distribution of arable land both in 2000 and 2013,we analyzed the temporal and spatial changes of arable land and the dynamics of arable land landscape pattern in the South of Songnen Plain.Second,based on Matlab,we established the quality evaluation system and developed SVM_GUI arable land quality evaluation model on goal of arable land quality classification to evaluate the arable land quality in the South of Songnen Plain.Finally,we analyzed dynamic changes of arable land quality and assessed the relationship between arable land quality and Normalized Difference Vegetation Index,Net Primary Productivity and Vegetation Coverage.Conclusions were summarized as follows:(1)Arable land area in the South of Songnen Plain increased from 5.61×104 km~2 to 5.64×104 km~2 from 2000 year to 2013 year,among which dry land increased by 645.36 km~2 and paddy land decreased by 350.91 km~2.The transformation between dry land and paddy land were frequent.Distribution of arable land changed differently from east to west: increased in east part of study area and decreased in west part,which resulted to the gravity center of arable land moved toward west obviously.The increased arable land mainly converted from wetland and grassland,accounting for 66.04% and 21.12% of the total change area.The lost arable land mainly turned to artificial area,woodland and wetland in traditional farming area,accounting for 45.08%,28.85% and 22.61% respectively(mainly distributed around Changchun city).The speed of wetland converted into arable land was much higher than the speed of the arable land transformed into arable land.The conflicts between Grain to grass & wetland and arable land expansion are still outstanding in the South of Songnen Plain.(2)The centroids of arable land gradually moved to the northwest,of which the centroid of paddy land shift the biggest distance.The landscape indexes of arable land had fluctuations in the study area.The landscape dominance of arable land increased continuously and the Shape of arable land gradually become in rule.Fragmentation degree of arable land declined.The dry land’s landscape dominance increased but paddy land’s decreased.(3)Based on Matlab,we developed SVM_GUI arable land quality evaluation model.The evaluation results analysis showed arable land qualities were mainly in medium to high level in the South of Songnen Plain and the quality of arable land decreased t from east to west.In the past 14 years,although the total area of arable land increased,the quality grade of increased arable land were lied in lower quality grade,belonging to third,fourth and fifth class accordingly,accounting for 235.62 km~2,148.08km~2,217.82 km~2,respectively.This phenomenon mostly happened surrounding regions of Baicheng and Songyuan.Besides,the area of arable land in first class decreased by 304.89 km~2,which mostly happened surrounding regions of Changchun City.(4)The arable land quality has closely related with and grain yield,NDVI,NPP,FVC and EVI.The result indicated significantly related that R2 was 0.29、0.41、0.3、0.39、0.31,respectively.It is possible to evaluate the arable land quality according to crop condition and crop yield.This study provides a new idea for monitoring and sustainable utilization of arable land resource using remote sensing.(5)Urbanization is the most important driving factor to affect arable land quality and quantity.Build-up land expansion led to high quality arable land erosion seriously in the South of Songnen Plain.With the rapid urbanization of the rural region of the cities,more and more high quality arable land were occupied and the newly increased arable land reclaimed from salinized or alkalized land and wasteland,which lead to the area of arable land increased but quality of arable land decreased.Overall,the arable land in the South of Songnen Plain degraded severely.The quality of arable land degraded obviously and most increased arable land were in lower quality grade.This paper can provide an important guiding significance for food security and sustainable development of arable land resource.