SOIL ORGANIC CARBON STORAGE AND ITS SPATIAL-TEMPORAL VARIATION IN THE CENTRAL AND WESTERN AREA OF JILIN
吉林中西部地区土壤有机碳储量及其时空变化特征

Using the measured data of the multi-purpose regional geochemical survey,we estimated the SOC densities and reserves of surface soil in the central and western area of Jilin.The result shows that at the distribution of the different depths,SOC accumulation at the surface layer(0~0.2m)is weak,whose SOC reserve only accounts for 23.8%of the whole layer(0~1.8m),while the reserve of the upper layer(0~1.0m)accounts for 95.7%of the whole layer.From the soil type,the soils with high surface SOC densities are dark brown soil(6363.8±3900.5t/km2),chestnut soil(5001.9±1313.2t/km2),white pulp soil(4629.8±1921.5t/km2)and paddy soil(4193.6±1509.6t/km2)etc; the soils whose reserves are rich are chernozem(66.969±25.460Tg),dark brown soil(65.929±40.410Tg),black soil(46.837±14.553Tg)and new plot soil(43.368±20.910Tg)and so on.With respect to the land use,paddy field(4150.2±1813.8t/km2)and woodland(4133.4±3450.2t/km2)have the highest surface SOC densities; dry farmland(140.186±52.156Tg)and woodland(104.442±87.180Tg)have the highest surface SOC reserves,both of which account for 75.6%of the total reserve of surface SOC.From the perspective of spatial distribution,the SOC densities in the central and western area of Jilin are northwest low,southeast high,roughly showing a trend of gradual increase from northwest to southeast.The zone with lower carbon density includes most parts of Baicheng and Songyuan,western part of Siping,while the zone with higher carbon density includes Jilin,Liaoyuan and Changchun,and the area of these three regions accounts for only 1/3 of the whole area but concentrates half of the surface SOC total in the whole area,of which Jilin has the highest SOC average density,reaching 6305.8±4018.8t/km2; in addition,the northwest part of Baicheng has also high carbon density.We carried a comparison research with the date of the Second Soil General Survey and found that the average surface SOC content changes from 1.45±0.80%to 1.24±0.82%,the average density decreases from 3834.7±1087.5t/km2 to 3436.7±2249.7t/km2,and the reserves decreases from 366.167±103.840Tg to 328.165±150.124Tg,with a net decrease of 38.002Tg; Organic carbon releases from soil to atmosphere with an annual change rate of 0.199tC/ha ·a,of which marsh soil,albic soil and dark brown soil have faster carbon release rates,so the surface soil in the central and western area of Jilin plays a role of carbon resource in the regional carbon cycle.