Distribution Characteristics Of Carbon Stocks In Urban-rural Interlocking Belt In Chengdu

Urbanization has become a global phenomenon, accompanied with a series of regional climate problem, especially greenhouse effect which main caused by carbon dioxide. In order to mitigate regional greenhouse effect, it is important to realize the effect of urbanization on regional carbon dioxide. It is the key that analyze the effect of urbanization on regional soil and vegetation carbon stocks, and reveal the effect machine. Our article selects the urban-rural interlocking belt as study area, analysis the urbanization process, estimate SOC density/stocks, SIC density/stocks and vegetation C stocks, and choose the land use, construction density, road density, the distance from urban core, population and economic and urban soil age as urbanization factors, discuss the effect on SOC density and SIC density, reveal the effect machine, in order to provide reference for mitigate greenhouse effect. The main research result as following:(1) Wenjiang urban area expansion develop rapidly from 15% to 56%, half of area finished urbanization. Regional land use convert from rural land use to urban types, as cultivated land and forest land to construction and road. Urban area laterally distribute from west to east, and rural area distribute in north and south of region. The expansion of urbanization from east and west side to middle area, and from west to north and south area. The expansion types present industry land, residential land and road. Total population of Wenjiang district increase nearly 90 000, and present stable growth trend. Regional GDP expand 6 times, per net income of farmers and urban resident disposable income growth respectively to four times and three times as much. The rapid growth of population and economy promote the improvement of regional urbanization level, rapid urbanization influence soil carbon pools.(2) SOC density ranged from 0.63?9.05 kg C m-2, with a mean value of 2.81 kg C m-2. SIC density ranged from 0.02-0.23 kg C m-2, with a mean of 0.12 kg C m-2. SOC density/stocks show decreasing trend from up to down in the soil profile, by contrast the SIC present opposite trend. SOC and SIC density present lower in urban area than rural area from spatial distribution. Total carbon stocks among land use types present following, land with tree is 279.08×106 kg, paddy field is 238.37×106 kg, impermeable surface is 237.30x106 kg, vegetable field 125.92×106 kg, urban green space is 103.30×106 kg, land with shrub is 67.26×106 kg, unoccupied land is 65.56×106 kg, nursery garden is 29.57×106 kg. Regional total carbon stock is 1146.35×106 kg, SOC stock is 1083.93X106 kg, SIC stock is 46.67×106 kg, vegetation C stock is 15.75×106 kg.(3) The SOC densities of urban land types as construction land, road, industry land, road grass, road woodland, residential grass and residential woodland are significantly lower than rural land use types, the SIC densities of industry land, road grass, road woodland and residential grass are significantly lower than rural land use types. The effect of construction on SOC and SIC density is same as road density, in surface 0-40 cm layer, SOC and SIC density decrease with construction and road density, and in bottom 40-100 cm soil layer, SOC and SIC density increase with construction and road density. By contrast, SOC and SIC density increase with the distance from urban core in surface 0-40 cm soil layer, and decrease in bottom 40-100 cm layer. There are the better population and economy situation, the lower SOC and SIC density. Soil would accumulate SOC and SIC with increasing urban soil age.(4) In urbanization process, soil will loss SOC and SIC during the conversion from rural land use to urban land use. Accompanied increasing construction and road density, closer to urban center, there are higher urbanization level, where the SOC and SIC density is lower. Urbanization lead to soil loss SOC and SIC. During urbanization, artificial disturbance on soil result in the decomposition of soil organic matter and carbonate, is the basis factor to effect on SOC and SIC density of urbanization. Urban soil will accumulate SOC and SIC with increasing age until compensate for SOC and SIC during land conversion. In order to mitigate greenhouse effect, one hand we need to reduce artificial disturbance on soil, and decrease the decomposition of soil organic matter and carbonate. On the other hand, we need to improve the management of urban green space to enhance the ability of accumulation C.