Using Different Methods To Estimate The Soil Organic Carbon In Densely Populated Rural

Basing on high-resolution satellite remote sensing image,GPS and GIS technologies, Soil Organic Carbon pool(SOCP) of a densely populated village-scale district was estimated in Sichuan Hilly Region.The spatial characters and influence factors of soil organic carbon density(SOCD) and SOCP were analyzed in the region.Besides, estimating values of different methods were contrasted with verification data.Finally,by analysis the error and applicable condition,the best means were been found.The main results were as follows.(1) In ecotope classification,SOCD were between 0.31～2.37kg/m~2,and the average value was 1.04kg/m~2,and total SOCP was 19.18×10~6kg.In plane distribution,from central hill to all sides,SOCD increased with height decrease.In soil vertical profile,SOCD was asymmetric,and surface layer was more than bottom.SOCP had the significant diversity in different ecotope types.Rotation paddy field,foothill dry field and single season planting field had a half of total SOCP,reaching 49.58 percent.SOCP was accord as ecotope area. However,due to the depth profiles and soil organic carbon density,foothill dry field, rotation paddy field,single season planting field and non-irrigation field were different.(2) In soil type classification,SOCD were between 0.43～2.22kg/m~2,many more were between 1.09 to 1.43 kg/m~2.The average SOCD was 1.16 kg/m~2,and total SOCP was 20.35×10~6kg.SOCD of paddy soil distribute area was more than yellow-red-purple cobblel sand soil and yellow-red-purple sand silt soil.Paddy soil SOCD in all soil profile had a high level of value,and the decline was not significant.Other soil types,only surface layer had the high value,and reduced significant.Brown-purple soil SOCP was 10.39×10~6kg,reaching 51.05 percent of total SOCP.The area ratio of gleyed paddy soil and waterloggogenic paddy soil was higher than SOCP ratio.(3) In land coverage classification,SOCD were between 0.63～2.16 kg/m~2,and the average SOCD was 1.01 kg/m~2,and total SOCP was 20.86×10~6kg.SOCD changed with height decrease,high-value agglomeration distributed in the strip around;mid-value agglomeration ring around the central layer of hill;low-value agglomeration scattered in the area.Less than 0.75 kg/m~2 SOCD agglomerations were construction land coverage and water area,and more than 1.09 kg/m~2 was hydrophily crop coverage.Xerophil crop and hydrophily crop SOCP were 11.77×10~6kg and 5.14×10~6kg,accounting for 81.06 percent of total SOCE In soil vertical profile,the total weight and all levels of SOCP of hydrophily crop coverage were more than xerophil crops.Furthermore,Area ratio of xerophil crops coverage was less than SOCP ratio,but hydrophily crop coverage was more than SOCP ratio.(4) In all impact factors,agglomeration area had significant positive correlation with the SOCP(R=0.9492);hypsography had great impact to SOCP by contrary change.Slope deposit developement soil had the most SOCP,by 14.56×10~6kg,residual deposit development soil had the lowest SOCP,only 0.42×10~6kg.Different land use patterns, SOCD and SOCP were differences.Irrigation land had higher SOCD but lower SOCP. Paddy field and upland had less SOCD but more SOCP.Rice-rape and Rice-Wheat panting mode had higher SOCD,and wheat-corn and rape-corn panting mode had larger SOCP.(5) Through average relative error and error analyse,ecotope and land-cover classification were optimum.However,taking into scale,work,work difficulty,precision, accuracy and other factors,the ecotope classification was optimum.If estimating in regional or country scale,select multi-methods could reduce workload and obtain accurate value.