| Taking different forests of Fengyang Mountanin in Zhejiang Province for instance, thechanges of soil organic carbon, soil labile carbon, organic carbon in aggregates of naturalsecondary forest and plantation had been compared in this research, The results showed that:(1)The content of soil total organic carbon and labile carbon of plantation were higherthan natural secondary forest. With the deepening of soil layer, the changes were reduced.Theaverage soil organic carbon content ranked in the order of Cunninghamia lanceolata forest of35years old（11.11g·kg-1）＞Coniferous and broad-leaved mixed forest of35years old（10.10g·kg-1）＞Cryptomeria fortunei forest of30years old（9.75g·kg-1）＞Evergreenbroad-leaved forest of40years old（9.57g·kg-1）＞Cunninghamia lanceolata forest of40yearsold（9.24g·kg-1）＞Coniferous and broad-leaved mixed forest of30years old（8.95g·kg-1） at0-60cm depth. The soil organic carbon density ranked in the order of Cunninghamialanceolata forest of40years old（1.18kg·m-2）＞Cunninghamia lanceolata forest of35yearsold（1.17kg·m-2）＞Evergreen broad-leaved forest of40years old（1.15kg·m-2）＞Cryptomeriafortunei forest of30years old（1.06kg·m-2）> Coniferous and broad-leaved mixed forest of30years old （1.05kg·m-2）＞Coniferous and broad-leaved mixed forest of30years old（1.03kg·m-2）; The highest content of soil labile carbon was in the Chemically Stable Carbonat2.3251g·kg-1and the lowest was in the Water Soluble Organic Carbon at0.2480g·kg-1.(2)Seasonal influence on soil total organic carbon of different forests was small butseasonal influence on soil labile carbon was large. With the deepening of soil layer, thechanges were reduced.The soil organic carbon content of Evergreen broad-leaved forest insummer and spring were higher than in winter and autumn; The soil organic carbon content ofCunninghamia lanceolata forest and Cryptomeria fortunei forest in winter and spring werehigher than in autumn and summer; The soil organic carbon content of Coniferous andbroad-leaved mixed forest in spring and winter were higher than in autumn and summer. Theminimum value of WSOC appeared in summer at0.2223g·kg-1. Seasonal influence on ROCfeatured as summer firstly, spring secondly, autumn thirdly and winter lastly and themaximum value was1.1777g·kg-1.(3)Through the analysis of correlation existing between various nutrient factors, the resultshowed that soil physical and chemical properties significantly affected soil organic carbonand soil labile carbon. It showed significantly positive correlation among different types ofsoil organic carbons above the coefficient of0.903.Fitting precision of monadic linearregression equations were above90%,which showed that there was a closed connectionbetween soil nutrients and soil organic carbons. (4)The soil granule structure was dominated by macro-aggregate(>5mm),micro-aggregate（<0.25mm）contained less.It showed obvious differences between natural secondary forestand plantation.The soil aggregate ratio of organic carbon in the middle size were the highest at16.34g·kg-1for0～20cm soil layer and it was in <0.5mm aggregate at10.09g·kg-1for20～40cm soil layer. The soil aggregate ratio of ROC in the middle size were the highest for both0～20cm and20～40cm soil layers. The highest value for chemically stable carbon of naturalsecondary forest was in <0.5mm aggregate. However, the highest value for chemically stablecarbon of plantation was in>0.5mm aggregate.The contribution rate of <0.5mm aggregate onsoil organic carbon and labile carbon was lower than17%, but the>5mm aggregate’scontribution rate was higher than32%. |
