Soil Carbon Source/sink Caused By Land Use Change In The Last Decades Of The Last Century In Eastern China

Soil organic carbon density(SOCD)under different land use and the effect of soil carbon source/sink caused by land use change in East China was investigated under different land use using soil organic carbon data and land use grid data of two temporal:the year of 1980 and 2000.254600 samples of soil organic carbon data were obtioned from regional multi-purpose geochemical survey.The results indicated:1)in East China SOCD,varied significantly with different landuses;the total surface SOCD is 2.90 kg/m2;forest and swmap have the higher SOCD,and water,construction land and other unused land are the landuse types with low SOCD;2)the reserve of surface soil(0-20cm)organic carbon in East China is 9.43Pg(9.43×1012g);the reserve of surface soil(0-20cm)organic carbon with land use in the order:forest land>cultivated land>gradd land>construction land>water>unused land(reserve 4.68Pg,3.33Pg,0.62Pg,0.33Pg,0.27Pg,0.20Pg,respectively);the two most large soil carbon pools are the forest land and the cultivated land,which account for,respectively,49.63%and 35.31%of the total organic pool of the study area;3)the typical landuse change types that caused soil carbon sinks are the change of dry farm land to paddy field,the change of dry farm lang to thick forest,and the change of other forest to thick forest;and the typical landuse change types that caused soil carbon sources are the changes of paddy filed to dry farm land,the change of thick forest to dry farm land,and the change of other land use to construction land,etc;4)the total carbon source caused by land use change is 71.49 Tg(71.49×109g),and the total carbon sink is 40.79Tg,so the aggregate effect of the land use changes results in an effect of soil carbon source of 30.7Tg in East China,annually carbon loss is 1.53TgC/yr during the year of 1980 and 2000.