Distribution Of Fresh Carbon In Different Soil Aggregates

Using the stable carbon isotope (δ13C) technique, an indoor incubation experiment was carried out to study distribution of fresh carbon in soil aggregate fractions. Soil samples were collected from the region of Wuyi mountain. To trace dynamics of fresh carbon in soil aggregates,1)1%13C-labelled rice straw was applied to the soils in Wuyi mountain, which were then put under incubation at15℃and25℃for360days;2)0.25%,0.5%,1%,2%,3%,4%, and5%13C-labelled rice straw was applied to the paddy soil in Jianou, which were then put under incubation at25℃for360days;3)1%13C-labelled rice shoot and rice root were applied to the paddy soil in Jianou, which were then put under incubation at25℃for360days. The study will provide scientific insights on distribution, dynamic and turnover of soil organic carbon applied plant materials. The major results are summarized as follow:Results showed that the mass distribution of different soil aggregate fractions followed a decreasing order of250-2000μm>50-250μm<50μm in all soils from Wuyi mountain at15℃and25℃. Meanwhile the contents of soil organic carbon in soil aggregates also have the similar trend, accounting for56%-80%of the total soil organic carbon in lager size aggregate.Results showed that the proportion of the fresh carbon in soil aggregates followed a decreasing order of250-2000μm>50-250μm<50μm in all soils from Wuyi mountain at15℃and25℃, accounting for60.1%-78.3%(15℃) and66.2%-76.99%(25℃) in lager size aggregate. The fresh carbon was controlled by native soil organic carbon content, and there was a negative correlation at25℃.Results also showed that the proportion of the fresh carbon in soil aggregates followed a decreasing order of250-2000μm><50μm>50-250μm in0.25%treatment, but250-2000μm>50-250μm><50μm in5%treatment. The rice root addition campared with rice shoot application all show that250-2000μm is significantly higher than other aggregates, there’s no significant difference between50-250μm and<50μm, and there is significant difference between two treatments for<50μm.