凋落物及氮添加对针阔叶林土壤活性有机碳的影响

In order to explore the effect of litter on forest soil nitrogen and the regulation of nitrogen deposition, this study was carried out considering the subtropical natural broadleaf forest and artificial coniferous forest soil and litter. Four treatments were designed, such as soil (control), soil with litter addition (3 times litter addition), soil with nitrogen addition (120mg/kg), and soil with both litter and nitrogen addition (3 times litter addition, and 120mg/kg), in the leaching experiment for one year. After incubation experiment, soil soluble carbon in bulk soil and soil readily oxidized organic carbon (ROC) in particle size fractions by physical classification were analyzed.The results showed that, compared with the control, litter addition in coniferous forest increased the total soil soluble sugar, while litter decreased the total soil soluble sugar in broad-leaved forest; under the condition of litter addition, nitrogen addition significantly increased soil DOC and soluble sugar content in coniferous forest. The distribution proportion of each soil particle size fraction was found significantly difference. Nitrogen addition tended to reduce the proportion of the large particle size and increase that of small particle size for coniferous forest soil, while broadleaf forest was observed inverse. Nitrogen addition to coniferous forest soil significantly reduced the ROC content of soil particle size components >2000μm, 53-20μm, 20-2μm.Litter addition significantly reduced the ROC content of 250-53μm, 20-2μm particle size. The co-addition of litter and nitrogen increased the ROC content of 2000-250μm, 250-53μm particle size. In broad-leaved forest soil nitrogen addition or litter addition decreased the ROC content of 53-20μm particle size, but had no effect on 250-53μm particle size, and the other particle size components increased the ROC content. Litter and nitrogen additions significantly increased the ROC content of >2000μm, 2000-250μm, and <2μm particle size in broad-leaved forest soils. It can be concluded that the ROC of different forest types in response to litter and nitrogen addition treatments has significant differences, which is expected to provide a reference for scientific management and carbon management of subtropical forest stands.