Study On The Dynamics Of Soil Carbon In A Secondary Oak Forest And A Pine Plantation In North Sub-tropical Area, South-eastern China

The dynamics and its main influence factors of soil organic carbon, soil labile carbon, soil microbial biomass carbon, soil respiration and plant litter fall input were studied in a secondary oak forest and a pine plantation in Xiashu Forest Experimental Site of Nanjing Forestry University, Jiangsu Province, South-eastern China. The field experients lasts two years with randomized block design. The results showed that: (1) There were significant diurnal variation and seasonal variation of soil respiration both in oak forest and pine plantation, the seasonal variation of soil respiration was mainly controlled by soil temperature, which was maximum in summer and minimum in winter, the Q₁₀ value in oak forest was higher than in pine plantation; (2) There were significant seasonal fluctuations of soil microbial biomass carbon both in secondary oak forest and pine plantation, which maintained at a lower level through the growing season in summer, but at a higher level during non-growing season in winter, the fluctuation of soil microbial biomass carbon wasn't directly regulated by soil temperature, soil moisture, or aboveground litter fall input, which might be regulated by the availability of soil carbon and soil nutrients or competition for soil nutrients from plant roots at local scales within northern subtropical forests; (3) Land use change significantly influenced the soil respiration and soil microbial biomass, the land use change from forest to cropland may potentially increase the release of soil carbon dioxide; (4) There were determinate seasonal fluctuations of soil organic carbon and soil labile carbon in both secondary oak forest and pine plantation, but the characteristics of the seasonal fluctuations of soil organic carbon or soil labile carbon were different with different land types and different treatments, there were apparent downtrend of soil organic carbon in both oak forest and pine plantation, but the downtrend in oak forest was more significant than in pine plantation, the input and decomposition of plant litter fall had important influence on maintaining the pool size of soil organic carbon and soil labile carbon.