Abstract:

In order to understand the biodegradation and the role of DOC in carbon cycle in farmland ecosystems, with incubation experiments, the author selected three kinds of paddy soil which were the red paddy soil, huangni soil and wushan soil, and then extracted the DOC from paddy soil to estimate the biodegradation of the DOC. The results showed that: the DOC content and three kinds of paddy soils were 31.64-49.25 g/kg, wushan soil had a slightly higher DOC content than huangni soil, while red paddy soil had the lowest DOC content. During the 42 days of incubation, there was a broad range of biodegradation DOC (from 54.8% to 66.6% of total DOC), and decreased in the order of huangni soil, wushan soil, red paddy soil. The law was consistent with a double exponential decay model. DOC was composed of two different degradation rate constituents which were labile DOC and refractory DOC, the turnaround time of easily degradable part (labile DOC) was within 1-2 days and the turnaround time of hard degradable part (refractory DOC) was within 64-278 days. During the incubation, the ratio of complex structure dissolved organic matter in DOC solution increased in the period of early incubation, and then declined in the late period, which was related to the rapid biodegradation of labile composition in DOC solution.