Perspectives on issues of soil carbon pools and global change -With suggestions for studying organic carbon sequestration in paddy soils of China

Carbon sequestration is one of the research targets for mitigating the carbon sink saturation trend and seeking feasible carbon management strategies of terrestrial ecosystem.Soil organic carbon(SOC)has been shown as one of the largest and most mobile carbon pools of the earth surface ecosystem.For the last decade,increasing attention has been given to the SOC pool change in relation to the sink or source effect of air CO 2 and to the dynamics under global change scenarios.Carbon sequestration agriculture has been recognized as the key approaches to sustainable agriculture in western countries.The research of SOC sequestration has been increasingly directed to SOC partitioning and binding behavior in soil aggregates(soil particle fractions)by constitutional characterization with modern SOC structure analysis technologies such as 13 C NMR.The lability of SOC has become one of the research foci in understanding the long term effects of SOC pool under climatic change and environmental stresses.However,uncertainty of SOC turnover is still in debt when interpreting the results from short term laboratory incubation by using both soil warming and air CO 2 doubling treatments.Despite of arguments on the general SOC loss,an increasing trend of SOC in paddy soils has been evidenced by many pilot experiments and statewide soil survey data since 1980s in China.Nevertheless,less is understood on SOC distribution,binding mechanisms in paddy soils of China and their changes in response to agricultural practices,soil fertility evolution and environmental stresses.Interaction of physical,chemical and biological features in paddy soils,association of SOC with mineral and bioorganic materials in aggregates deserves urgent research needs.