Soil Carbon Turnover Characteristics And Its Influential Factors In Bamboo Forests

Soil carbon turnover characteristics in bamboo forests has been studied using laboratory and field experiment. Soil adsorption capacity and several soil carbon turnover indications e.g. soil organic carbon, soluble organic carbon and microbial biomass carbon were determined to study the fixation and release of carbon in the bamboo forest soil. The main original conclusions were shown as follows:1. All the three models including IM, Langmuir, Freundlich and Temkin isotherm models can successfully describe soluble organic nitrogen (SON) and soluble organic carbon (SOC) sorption phenomena under low sorption concentration in the bamboo forest, tea garden and pear orchard soils. However, these models cannot suitable for the high concentration range except Langmuir equation. The three soils had similar adsorption ability of SON. Variation of SOC adsorption was observed among different soils with the following order:bamboo forests soil> tea garden soil> pear orchard soil. More adsorption of SON than SOC suggested the high potential of SOC leaching from soils. Compared with the original soil, the adsorption rates of SON and SOC were higher in the soil without free iron and aluminium oxide and lower in the soil without amorphous iron and aluminium oxide. The adsorption rates of SON rate increased but the adsorption rates of SOC rate decreased in the soil when organic matter was removed.2. The dynamics of soil organic carbon and microbial biomass carbon were investigated in bamboo (Phyllostachys pubescens) forests in the Taihu catchment. The results showed that there were no significant difference of soil organic carbon among different seasons and fertilizer treatments. The content of soil soluble organic carbon (SOC) ranged from 102.5 mg·kg-1 to 200.2 mg·kg-1, and the content of microbial biomass carbon ranged from 150.8 mg·kg-1 to 431.3 mg·kg-1. Soil SOC was significantly higher in January than July (p=0.0220), while microbial biomass carbon in January was significantly lower than that in June (p=0.0087). Compared with CK, SOC content in FFP significantly reduced (p=0.0107).3. The dynamic of soil respiration and its influential factors under field conditions were investigated in bamboo (Phyllostachys pubescens) forests in the Taihu catchment. The results showed that the soil temperature in 5cm depth was significantly correlated with air temperature. Soil respiration appeared single-peak curve and soil respiration rates were significantly correlated with the soil temperature. The minimum of soil respiration rates appeared in January with CK 0.13 g·m-2·h-1,SSNM 0.14 g·m-2·h-1, FFP 0.17 g·m-2·h-1 and the maximum was in July. Soil respiration rates had no significant difference in different soil water contents and fertilizer treatments. The total amount of CO2 released from bamboo forests soils during a year can be obtained using the model F=a·ebT, which were 50.24t-hm-2 in CK,49.87 t·hm-2 in SSNM and 50.72 t·hm-2 in FFP.