氮沉降对杉木人工林土壤团聚体及其有机碳分布的影响

Distribution of Water-stable Aggregates and Organic Carbon in Response to Simulated Nitrogen Deposition in a Chinese Fir Plantation

在杉木人工林中开展模拟氮沉降实验,设计N0(对照)、N1(60kg/hm2)、N2(120kg/hm2)和N3(240kg/hm2)4种氮沉降水平,通过对杉木人工林进行8年模拟氮沉降试验后,研究土壤水稳性团聚体及其有机碳的响应。结果表明:1～0.5mm粒径水稳性团聚体含量在各氮沉降处理占总水稳性团聚体的比例均最大,<0.053mm粒径的含量最小。各级团聚体含量从高到低依次为1～0.5mm,>2mm,2～1mm,0.5～0.25mm,0.25～0.053mm,<0.053mm。与对照(N0)相比,中低氮处理(N1、N2)提高了水稳性大团聚体(>0.25mm)的含量以及团聚体平均重量直径,而高氮处理(N3)表现出一定的抑制作用。各氮沉降处理中,>2mm粒径的团聚体有机碳含量最高,但处理间差异不显著。土壤水稳性团聚体有机碳储量在氮沉降处理下有所增加,以低氮处理(N1)最高,说明氮沉降增加在一定程度上促进了土壤的固碳潜力。

The effects of 8-year-long simulated nitrogen deposition on the distribution of water-stable aggregates and concentrations of soil organic carbon in a Chinese fir plantation located in Sanming,Fujian province were investigated.Nitrogen loadings were designed N0(control),N1,N2and N3at the doses of 0,60,120,240kg/hm2,respectively.Bulk soil samples was separated into six aggregate-sizes(>2mm,1～ 2mm,0.5～1mm,0.25～0.5mm,0.053～0.25mm and <0.053mm)and the associated soil organic carbon contents were determined.Results showed that the size groups of soil water-stable aggregates were in the order of 1～0.5mm,>2mm,2～1mm,0.5～0.25mm,0.25～0.053mm,<0.053mm.Compared with the control(N0),N1and N2treatments significantly increased the content of water-stable aggregates(>0.25 mm)and soil aggregates mean weight diameter,but N3treatment showed inhibition effect.Contents of soil organic carbon was highest in>2mm fraction of soil aggregates,but no significant difference was found among treatments.Nitrogen additions promoted carbon stocks of soil water-stable aggregates,which was highest in N1treatment.Results indicated that increasing of nitrogen deposition would increase the potential of soil carbon sequestration in the subtropical regions.