Soil Organic Carbon Density, Storage Spatial Distribution And The Analysis Of The Influencing Factors In Hunan Province

According to the second soil survey data of Hunan Province, this thesis estimated the organic carbon density and storage of the main soil types in Hunan Province. ArcGIS has been adopted for the study and analysis of the spatial distribution patterns of the soil organic carbon density and the causes that contribute to it. The thesis, with the data of the forth forest resources plan design and inventory report as the reference point, estimated the organic carbon density, the storage and the characteristic of the spatial distribution of the surface soil of different forest types in Hunan Province. It also provides valuable data for the evaluation of the role of Hunan soil in regional carbon balance, and for the research of national carbon cycle. The results show that:1. The soil organic carbon density, carbon storage and characteristic distribution of the main soil types in Hunan Province:The total storage of terrestrial soil organic carbon in Hunan is about 1.845×10 t. Carbon storage in various soil types is arranged in decreasing order:red soil> paddy soil> yellow soil> calcareous soil> yellow brown soil> purple soil> alluvial soil> coarse bone soil> Mountain Meadow soil> rocky soil. The organic carbon density of the main soil type in Hunan Province range between 66.42-183.97tC·hm-2 and the average density of the organic carbon is 116.30 tC·hm-2. The average organic carbon density of different soil types in Hunan Province below is in decreasing order:mountain meadow soil>yellow brown soil>paddy soil> rocky soil> yellow> red soil> calcareous soil> coarse bone soil> alluvial soil> purple soil. The spatial distribution pattern of the soil organic carbon density in each region of Hunan is relatively well-distributed and the soil organic carbon density is mainly range between 90-140 tChm·2.2. The soil organic carbon density, carbon storage and characteristic distribution of surface soil (0-20cm) in Hunan Province.The differences of the density of the surface soil organic carbon (0-20cm) was small, changing in the range of 40.19tC·hm-2-44.12 tC·hm-2, with an average of 42.31 tC·hm-2. The difference of the density of the surface soil organic carbon in five different geographical regions was also small. The southwest is higher than the northeast, and the order follows that: Southern Mountain>Western Region> The Middle Hilly area>Eastern mountain> Dongting Lake Plain Area. The storage of the surface (0-20cm) soil organic carbon is 713.69×106t, which is 38.68% of the soil organic carbon in Hunan Province. The spatial distribution of the reserve of surface soil organic carbon is similar to the terrain feature of Hunan. The south, east and the west is mountains, the middle is hills, the north is lakes and plains. Plains, mountains and hills are in opposite arrangement.3. Factors that influence soil organic carbon density, carbon storage in Hunan Province:The density of soil organic carbon is related to the precipitation and temperature in five natural geographic area of Hunan Province. But the climate is not the main factor that affects the spatial distribution of the density of soil organic carbon in Hunan province. The Soil organic carbon content (SOC) is related to the height(x)(p<0.05), which indicates that the soil organic carbon content increases with the elevation of altitude. The same type of soil has different parent rocks, then the organic carbon content is also different. Vegetation and soil are closely related, soil organic carbon content under different vegetation types are different. The order of soil organic carbon content under different vegetation types follows that:broad-leaved forest> fir forest> bamboo> economic forest> shrub forest> conifer Forest, Which shows that different types of vegetation make different contribution to soil organic carbon content. The results also shows that:the surface soil organic carbon is negatively correlated to the soil(ph)(p>0.05), soil organic carbon (SOC) and soil total N content was significantly positively correlated (P<0.01), and soil organic carbon and clay content were positively correlated (P<0.05).4. The SOC density and storage of the main types of vegetation soil (0-30cm) in Hunan Province.The soil organic carbon content of different forest types in Hunan Province varied from 12.25 to 19.30g·kg-1 The soil organic carbon content of surface was significantly higher than the deep soil. There are some differences between different soil organic carbon density of forest types, which varies from 31.722 to 45.854 tC·hm-2, and the average of the density was 32.11tC·hm-2, the decreasing order was that:bamboo forest> broad-leaved forest> economic forest> fir forest> conifer forest> shrub forest. The average density of soil organic carbon of different forest types decreased with the depth of soil. The total storage of organic carbon of forest soil (0-30cm) is 68641.81×104t, accounting for 37.18% of the total storage of soil organic carbon in Hunan. The storage of soil organic carbon in different forest arranges from 5063.28×104 to 16658.96×104t. And the storage of soil organic carbon in forest also decreased with the depth of soil.5. The density of organic carbon and the spatial distribution of the main vegetation surface soil (0-30cm) in Hunan Province.The weighted average density of soil carbon in forest is 62.67 tC·hm-2.It is in Yiyang city that has the largest weighted carbon density, is 64.78 tC·hm-2, and Xiangtan City has the smallest, is 61.11 tC·hm-2. And the density in other cities slightly changed from 61.11 to 64.78 tC·hm-2. Huaihua has the largest storage of soil organic carbon, is109.03×106 t, accounting for 15.88% of the total reserves of soil organic carbon in the forest in Hunan. The storage of soil organic carbon in forest in Xiangtan is 1.92×106t,which is the smallest. The storage of every type of forest follows the order:fir forest> coniferous forest> economic forest >broad-leaved forest> shrub forest> bamboo forest.