Processes And Mechanisms Of Soil Carbon Sequestration Under Three Forest Types In Dagang Mountain, Jiangxi Province

It gets more and more general approval of the international community to improve terrestrial ecosystem carbon through the afforestation and reforestation. The most direct impact is to increase the amount of vegetation and soil carbon sequestration for improving forest ecosystem carbon sequestration. At present, the estimation of vegetation carbon sequestration is relatively accurate, and soil carbon sequestration is researched quite weak. Butit is certain that soil carbon storage is very huge. A small change will cause the significant changes of atmospheric CO2. Therefore, it is necessary to study soil carbon sequestration and related processes in forest ecosystems for accurate assessment. Natural forest ecosystems have stable structure and rich biodiversity, and play an important role in conditioning atmosphere, water conservation, clean air, etc. So, we choosed 3 kinds of typical forest types that were Phyllostachys pubescens(PP), Castanopsis rargesn(CR) and Pinus massoniana(PM) in Dagang Mountain, Jiangxi province in China. Soil carbon storage was measured by distributed measuring method of soil carbon pole in forest ecosystem. Test plots were collected to investigate the effects of forest types on soil organic carbon, litter decomposition, fine root decomposition, soil respiration, soil carbon mineralization and microbial properties. Regulation mechanism of soil microbial biomass carbon, water soluble carbon and recalcitrant carbon to soil carbon stability was analysied byPath Analysis.Principal Component Analysis(PCA) was usedto evaluate comprehensive onsoil carbon sequestration. The main results are as follows:(1) Soil organic carbon stocks in CR and PP forest were higher than that in PM forest. The higher production and lower C/N of litter and fine root can accelerate soil carbon sequestration. However, the soils in PP forest contained more unstable carbon proportion, indicated by lower percentage of recalcitrant carbon. The higher lignin contents of litter leaf and fine root were conducive to soil carbon stability. Our findings highlight that future strategy of tree species selection in south subtropical China needs to consider the potential effects of tree species on the chemical composition of soil organic carbon in addition to the quantity of soil organic carbon stock.(2) The differences of soil carbon pool and fractions in different forests can be attributed to the differences of soil carbon input and output. The carbon input from litter leaf was higher in CR forest than in PP and PM forests, but carbon input of fine root was the highest in PP forest. The most of carbon input in soil biological decomposition process returned carbon dioxide to the atmosphere. Soil respiration and carbon mineralization rate were higher in CR forest than in PP and PM forests. It suggests those processes of soil carbon conversion led to higher soil carbon sequestration in CR and PP forests in contrast with PM forest. Therefore, the future strategy of tree species selection in China needs to consider the potential effects of tree species on soil carbon conversion process.(3) Based on carbon balance principle, principal component analysis method was used to comprehensivly assess soil carbon sequestration in the different forest types. The results showed that litter production and microbial biomass carbon were the main control factors of soil carbon dynamics, and the cumulative variance contribution rate of both was 100%. Our results contributed to the understanding of some important mechanisms by which tree species influence soil carbon sequestration.