Spatial Distribution and Variability of Topsoil Organic Carbon Content at Different Scales in Lu′an City,Anhui Province,China

Based on the field survey of 8 236 samples collected from Lu′an City for the Second National Soil Survey,different variation of spatial distribution of topsoil organic carbon content at different scales was studied.It turns out that organic carbon content varies in the tested soils dimensionally ranging from 4.58 to 60.38 g·kg^-1,which basically conforms to normal distribution.Comparatively,this dimensional variability is more obvious at county scale than at village scale,town scale and city scale,which means the dimensional scale has a significant impact on organic carbon content in topsoil and its estimation.In terms of different land use patterns,organic carbon content in non-cultivated soil (13.99 ± 2.19) g·kg^-1is notably higher than that in paddy soil (10.39 ± 1.58) g·kg^-1which is then remarkably higher than that in dry soil (8.44 ± 0.92)g·kg^-1.Moreover,non-cultivated soil boasts of the greatest dimensional variability with a variability index of 45.15%,much higher than that of paddy soil 17.19%,which is the lowest amongst the three land use patterns.In terms of different geomorphic types,the average content of organic carbon shows a tendency of mountainous region>hilly area>upland area>plain,the variability indexes displaying a tendency of hilly area>mountainous region>plain>upland area.These data suggest that human disturbance has exerted tangible influence on the topsoil organic carbon content.