Study on the Soil Organic Carbon Storage and Vertical Distribution of Several Forest Types in Mountain Area of Northeast Guangdong

There are four main forest types in Northeast Guangdong,and the forest types are natural evergreen broad-leaved forest,pine and broad-leaved mixed forest,P.Massioniana forest and artificial eucalyptus forest.Using the method of field investigation,soil sampling and laboratory analysis,the storage and distribution of soil organic carbon for the four main forest types in Meijiang district have been discussed.The results were as follow:(1) The average soil organic carbon content for the four forest types was 8.14～12.24 g/kg,the soil organic carbon content in evergreen broad-leaved forest was highest but lowest in eucalypt forest.Soil organic carbon contents generally decreased with depth,but decrease range was different for the four forest types,and change range of broad-leaved forest is highest(72.04%).The soil organic carbon assembled obviously in surface layer soils.(2) Soil carbon density in the four forest types change greatly,with a range of 1.57～5.18 kg/m2 for five soil depth intervals.Soil carbon density decreased generally with the depth,too.Soil carbon density under natural vegetation was significantly higher than that under secondary vegetation.For the whole soil section,soil carbon density in all forest types varied from 12.28～15.90 kg/m2,and their total mean values were 14.14 kg/m2.(3) The total mean value of carbon storage was 141.43 t/hm2 in the four forest types.By comparisons,soil carbon storage of the main forest types in mountain area of Northeast Guangdong was lower than that of other regions,and the four main forest types had lower proportion of carbon contained in the upper soil layer.These results showed that human impact was one of factors that exert a tremendous influence on soil carbon storage.