Abstract: To address the seasonal dynamics of soil organic carbon and its driving factors in different vegetation types in mountainous region of eastern Liaoning, the concentration and dynamics of soil organic carbon (SOC), soil dissolved organic carbon (DOC) and soil microbial biomass carbon (MBC) were examined in different soil layers of Larix gemlinii plantation, Quercus mongolica-Juglans mandshurica secondary forest, and Acer secondary forest. The relationships between SOC, DOC, MBC and biomass, soil physicalchemical and climate factors were also analyzed. Our results showed that the concentrations of SOC, DOC, MBC in different forest types displayed a vertical distribution with decreasing order of 0-10 cm>10-20 cm>20-30 cm. In addition, the concentrations of SOC, DOC and MBC in the Q. mongolica-J. mandshurica forest were higher than those of Larixforests and Acer forests. The concentrations of SOC, DOC and MBC had significant seasonal dynamics, with the highest concentrations in summer. The SOC and MBC had positive correlations with soil water content, pH and soil temperature, and had negative correlations with soil bulk density and precipitation. The concentration of DOC had positive correlations with soil water content, pH and precipitation, and had a negative correlation with soil bulk density. The concentrations of SOC, DOC and MBC had negative correlations with the stem and root biomass of tree and decomposition layer of litter, and had positive correlations with belowground biomass of shrubherb layer and biomass of semidecomposed layer of litter. The relationships between SOC, DOC and MBC and their driving factors were remarkably different among forest types, indicating that the interactive effects of forest type and climate made a unique microenvironment for different forest types, which affected the content and seasonal changes of soil SOC, DOC and MBC. The SOC, DOC and MBC storage in Q. mongolica-J. mandshurica forest were higher than those in other two forest types, indicating that it was beneficial to nutrient accumulation. The Q. mongolica-J. mandshurica forest is a suitable model for the construction and reconstruction of forest structure adjustment and soil restoration in the mountain area of eastern Liaoning.

Key words: fine root morphology, root bag method, plastic response, nutrient foraging, nitrogen deposition