Dynamics Change And Quantification Of Sequestration Potential For Soil Organic Carbon In Croplands In Liaoning Province

Soil carbon pool is a predominant component of global carbon cycle,with high incoming and outcoming carbon fluxes. As a kind of special soil, compared with natural soil, cropland is significantly disturbed by human activity, which large consequential carbon stock transfers with atmosphere. Source/sink of soil carbon has become a hot topic in the research field of soil science. So this paper taked Liaoning Province cropland SOC as research object, by the collection of historical data and processing of experimental data and method of GIS, clarified the dynamic evolution and storage, estimated soil sequestration potential aim to improve the SOC storage, establish target of fertilizing soil and alleviation greenhouse effect.The main results were as follows:(1) The average content of SOC for cropland decreased by 2.3g/kg in Liaoning Province during past 25 years. The contents reduced from middle to easthern, while increased in southern coast and west. A comparison of semivariograms of SOC between two periods(1980 and 2005) showed that both belonged to medium spatial correlation. The correlation distance showed that the distributed uniformities of two period SOC contents impaired, and variabilities intensify in small region, and the whole distribution is becoming complex.(2) The average SOC density was 9.27kg/m2 in one meter depth in the 2nd Soil Survey and decreased by 0.37kg/m2 in cultivated layer. The estimates of SOC storages to the depths of one meter and 20cm in cropland in 1980s were 313.52Tg and 97.65Tg, and 20cm in 2005 was 112.15Tg which increased by 14.5Tg since 1980.(3) CENTURY model can give better simulation of the dynamic evolution for SOC. Farming management measure in different phases has a greater effect on evolution of SOC; the general trend was declining slowly. The storage of SOC in cultivated layer declined from 112.15Tg to 104.68Tg in one hundred years since 2005.(4) The results of estimation of SOC sequestration potential with model which established based on long-term experiment showed that SOC density at the saturation state would reach an average of 4.74kg/m2 in cultivated layer. Using SOC density in 2005 as a reference, cropland soils in Liaoning Province are expected to sequester an additional 85.80Tg C, which could be achieved in 27-99 years when agricultural management is improved.