Study On Soil Organic Carbon Stocks And Soil Nutrients Spatial Differentiation In Jianghan Plain Using GIS

Soil carbon pool is the most important thing in terrestrial ecosystem carbon.The small changes in soil organic carbon could influence the concentration of greenhouse gases in the atmosphere causing the global climate change. Farmland soil was affected by human activities for a long time, so the organic carbon pool is also changing. As a result, the study that the estimation of soil organic carbon density and reserves, spatial variability and influence factors could provide the evidence for impvoving the concentration of soil organic carbon.This study based on the data of soil testing and fertilizer recommendation using the 3071 samples within the scope of Jianghan plain in Hubei province and established database of soil. GIS technology was used to study the top layer soil nutrient spatial variability characteristics, the density of soil organic carbon and organic carbon and their spacial changes in Jianghan plain and estimated the potential of soil organic carbon in J ianghan plain. In addition, this paper also explored the influence factors of soil organic carbon.The main results were as follows:(1) This paper researched the variability of soil organic matter, total nitrogen, total phosphorus, total potassium and p H, available phosphorus and available potassium of farmland soils in Jianghan plain. The results showed the variation coefficient from hight to low was available phosphorus, available potassium, total potassium, total nitrogen, total phosphorus, organic matter, p H value. The largest coefficient of variation was available phosphorus, so the available phosphorus was highly variable, the other indicators were belonged to medium variation. The research based on soil database of Jianghan plain showed that most of soil p H is neutral, but the area with more rivers and lakes were alkaline soil. The spatial variability characteristics of soil nutrient were mainly influenced by soil parent material, topography factors and fertilizer.(2) This paper calculated soil organic carbon density of different farmland soil types in Jianghan plain based on the soil spatial database using Arc GIS technology. The results showed the soil organic carbon density from hight to low was paddy soil, fluvo-aquic soil, yellow brown soil, purple soil, calcareous soil. soil organic carbon was consistent with organic carbon density. Paddy soil organic carbon density and reserves significantly greater than the dry land, and the proportion of organic carbon was similar to proportions of paddy field and dry land in Jianghan plain.The maximum and minimum of soil organic carbon density was Yingcheng and Tianmen city, respectively. The maximum and minimum of soil organic carbon pool was Jianli and Shashi city, respectively.(3)This study estimated the potential of carbon sequestration through a carbon sequestration potential model which was established based on the long-term trial in Jianghan plain. The results illustrated that the mean of organic carbon density in Jianghan plain was 3.33 kg/m2. the average of soil organic carbon sequestration potential(SOCP) was 8.18 kg/m2 and the soil carbon potential was 4.85 kg/m2. The spacial variability of SOCP was obvious in Jianghan plain. The SOCP in southwest was slightly higher than that of northeast region in Jianghan plain. The maximum and minimum of SOCP was Gong’an and Xiantao city, respectively. However, the growth potential of the largest carbon density was Zhijiang city and this change was in line with the distribution of the climate and soil properties. The soil organic carbon of top layer(0-20cm) under saturation value was 175.1907 million tons, so it could increase 103.8588 million tons of carbon sequestration.(4) This study explored the factors influenced soil organic carbon from natural and human management respects. the results displayed that some soil nutrient factors had a significant influence on soil organic carbon, they were total nitrogen, total potassium alkali solution nitrogen and CEC. The p H had poor correlation with soil organic carbon. Soil parent material and soil physical properties had a significant impact on soil organic carbon content. The soil organic carbon content from hight to low with diferent soil textures were clay loam soil, clay soil, loam soil, sandy soil, respectively. The soil organic carbon content from hight to low with diferent soil types were paddy soil, fluvo-aquic soil, yellow brown soil, respectively. The soil organic carbon content from hight to low with soil from diferent parent materials were crystalline rock weathered,red sandstone weathered, quaternary red clay, Carbonate rock weathered,river and lake sediments, argillaceous rocks weathered, respectively. Farmland management measures had important influence on soil organic carbon content, such as crop rotation system and irrigation level. The soil organic carbon content from hight to low with diferent irrigation level were fully satisfy, basic content, no- irrigation, respectively. The soil organic carbon content from hight to low with diferent rotation systems were oil-rice, vegetable-rice, wheat-rice, wheat-corn, citrus.