Effects of natural forest types on soil carbon fractions in north-east China

Tree species have strong influence on soil carbon storage but the interactions are not well understood. using the path analysis method,the response of soil carbon pool to changes in tree species were studied by comparing soil organic carbon quantity and quality in primary mixed broadleaved korean pine (pinus koraiensis and quercus mongolica),natural korean larch (larix olgensis) and natural chinese pine (pinus tabulaeformis) forests in north-east china. results showed that the effects of tree species on soil total organic carbon,recalcitrant organic carbon and microbial biomass carbon occurred at 0-40 cm depth. the mixed forest increased organic carbon and carbon fraction concentration over pure korean larch and chinese pine stands. path analyses suggested that the effects of tree species on soil organic carbon mostly passed through direct effects on recalcitrant organic carbon and indirect effects on microbial biomass carbon but not through water-soluble organic carbon. microbial biomass carbon may be used as a sensitive indicator of changes in soil organic carbon. moreover,the response of recalcitrant organic carbon to forest conversion will also determine the magnitude of feedback of soil carbon to forest type due to its large storage in soil. © forest research institute malaysia.