Evolution Of Soil Organic Carbon And Evaluation Of Carbon Sequestration Potential In Cultivated Land Of Lower Reaches Of Liaohe River Plain

Soil carbon pool is an important part of the global carbon cycle and can affect the global carbon balance. Compared with natural soil, the strength of the carbon exchange between cultivated land and atmosphere is increased due to human intervention. The research on soil carbon source and sink has become the hot topic in soil science. There are a lot of cultived land in lower reaches of Liaohe river plain and have played a key role in the carbon cycle in the Northeast of China. So the spatial and temporal variations of soil organic carbon (SOC), stock and carbon sequestration potential have been studied by using GIS technique. The main results obtained from the research are as following:(1) The SOC contents in farmland here were declined since1980. The differences of spatial distribution decreased gradually. SOC content in farmland in2010was5.05%lower than that in1980. From the changes in spatial distribution, the SOC contents appeared to increase in the south and decrease in the north. From a statistical point of view, SOC was medium spatial autocorrelation in1980and2010. The ranges of variations and the uniformity of SOC in the two periods were declined, but strengthened in a small range. The overall distribution inclined to be complexity in the past30years.(2) The land utilization type (dryland and paddy field) and the annual precipitation are the main factors influencing the changes of SOC. The SOC content reduced in dryland and increased in paddy field.(3) In the early1980s, the average SOC density in arable layer (0-20cm) was2.72kg m-2, which shows the trend of reducing from southeast to northwest in the spatial distribution; In2010the average SOC density was2.70kg m-2, which has no obvious difference in the spatial distribution. The SOC stock of arable layer in this area in1980was67.24Tg and66.53Tg in2010, with a decrease of0.71Tg.(4) The models of SOC sequestration potential in farmland here were established combining with the survey data and the field test data in past30years. The SOC sequestration potential (saturation) was predicated to reach4.95kg m-2, with an obvious spatial differentiation. According to the models established by latest survey data, the added value of density of SOC sequestration potential will be2.25kg m-2and SOC stock will be57.52Tg in farmland.