Effects Of Land Use Change On Carbon Fractions In Soil Aggregates

The soil organic carbon pool is about three times the biotic pool and twice the atmospheric pool.Any change in soil carbon pool will lead to change of atmospheric pool and climate change.About 25% of the current total anthropogenic emissions of CO₂ are estimated to be caused by land use change.It is essential to assess the impact of land use change on terrestrial carbon dynamic. It is not clear about soil processes and mechanisms of soil organic carbon stabilization,especially the effect of land use change on soil organic carbon.Herein it is need to evaluate the influence of land use on soil carbon fractions.The purpose of this research was to assess impact of land use on total organic soil carbon and soil carbon fractions in aggregates.Soil samples were collected from adjacent natural forest, plantation,secondary forest, agricultural land for comparison of total organic carbon,light fraction(LF) carbon,particulate organic matter(POM) carbon,microbial biomass carbon (MBC),free light fraction carbon(free LF C),intra-aggregate particulate organic matter(iPOM) carbon, mineral-associated carbon(mSOC). Understanding how these soil organic carbon fractions behave in response to changes in land use will aid in assessing sources and sinks of carbon associated with forest conversion in subtropical region of China.Total soil carbon, light frction carbon,particulate organic matter carbon, microbial biomass carbon in soil and soil aggregates decreased due to forest conversion,particularly in macroaggregates.LF C and POM C were sensitive to the change of land use,but MBC and MBC quotient had minimal impact on different land use.Total amounts of free LF and iPOM were significantly larger in the natural forest than in other land use practices.The results indicate that the iPOM accounted for much of the losses of soil organic carbon due to conversion.Therefore,the LF C and POM C were much more affected by forest conversion than the total aggregate organic carbon and MBC.Of the different POM fractions,losses of the iPOM due to conversion was more pronounced than free LF fraction.The observed changes in soil aggregation and SOM should provide a practical tool to complement further chemical, biological and physical soil tests to project a sustainable and productive agriculture in this environment.