Soil organic carbon(SOC)and its correlations with soil properties were studied under the four stand types of Larix olgensis natural forest

Larix olgensis plantation

natural mixed broad-leaved forest

and natural mixed coniferous and broad-leaved forest in the eastern part of Changbai Mountains.Results showed that the SOC contents had significant differences among different soil layers under the four stand types.The SOC content gradually decreased with the increase of soil depth

and SOC was mainly distributed in the topsoil(0-20cm).The average SOC content under the stand types followed the order of natural mixed coniferous and broad-leaved forest(33.64±17.48g/kg)>Larix olgensis natural forest(25.30±15.09g/kg)>natural mixed broad-leaved forest(22.13±13.74g/kg)>Larix olgensis plantation(19.23±12.35g/kg).The SOC density in 0-60cm layer under natural mixed coniferous and broad-leaved forest was 21.44±8.31kg/m2

higher than that under the other three stand types.In different soil layers

the correlations between the SOC density and soil physiochemical properties were different.The SOC content had significant negative correlations with soil bulk density

but positive correlations with soil moisture

soil total N and P

and available K.For different stand types

SOC had positive correlations with soil total N

but had great differences in correlation with soil properties.