| The soil carbon pool is the largest active carbon sink of the Earth system and the main carbon source of GHG. Soil carbon pool plays an important role in the global carbon cycle. Its accumulation, circulation and release have important influence on atmospheric CO2concentration. Carbonate area covers about one-third of the land surface of China, it is an important component of ehe earth surface system. It stores more than6.0×16t C, soil is the product of the long therm interaction of various spheres in the Earth system, also it is the support of spheres, and it is the largest carbon pool in global system. The land use types is the most important factor of affecting terrestrial ecosystem carbon cycling and carbon accumulation. Study of land use type affect the stability of soil organic carbon pool and change of the organic carbon pool components has an important theoretical and practical significance.Based on qualitative and quantitative analyses, the objective of this study is to understand soil organic carbon stability under different land uses. The mains tudy contains soil organic carbon fractions, three carbon pools and their turnover time and their infulence factors under different land use. The soil samples were taken from four different typical land uses (cultivated land, shrub, orchard and forest) in karst area and clasolite area respectively under the same micro-climate conditions. The soil samples were taken from0-20cm,20-40cm,40-60cm in all above landuses. Meanwhile, statistical methods were used to analyze and categorize indicators for the purpose of simplifying and selecting indicators, and find a few non-observation of latent variables to explain the original variables by factor analysis and cluster analysis. Thorough a large number of field work and laboratory experiments, the major resules are as follows:1. The four land types soil organic carbon contents is15.41-15.4120.10g/kg,13.07-31.16g/kg,9.3814.74g/kg,30.8237.52g/kg respecitively. In general, organic carbon contents in natural soil were higher than that in agricultural soil, and organic carbon content of0-20cm soil depth was greater than that of20-40cm and40-60cm.2.The results of soil organic carbon decomposition incubation experiment get the four land types soil organic carbon mineralization rate is forest land> shrub> cultivated land> orchard, the difference between40-60cm of is not obvious, show that the decomposition of organic carbon rate and total organic carbon storage size were positively correlated.3.On the base of first order dynamic model, combining with a laboratory soil incubation experiment, the dynamic of soil organic carbon (SOC) decompositions, three carbon pool sizes and average turnover time are analyzed, including cultivated land, shrub, orchard and forest four different land use types brown calcareous soil of typical karst area in Maocun of Guilin. The results show that four soil types t active SOC pool are0.094-0.188g/kg,0.124-0.308g/kg,0.094-0.113g/kg0.462-0.622g/kg respectively. The size of active SOC pool is smallest, respectively accounts to0.61-0.93%,0.95-1.24%,0.77-1.00%,1.49-1.66%. Slow SOC pool are12.06-13.85g/kg,11.17-23.45g/kg,5.36-10.27g/kg,21.66-68.12g/kg, respectively account to21.13-30.18%,13.58-23.46%,29.54-46.58%,30.39-33.84%, and the average turnover time is7a,8a,7a,12a respectively. The Passive SOC pool is largest, respectively12.06-13.85g/kg,11.17-23.45g/kg,5.36-10.27g/kg,21.66-68.12g/kg, and account to69.18-78.26%75.27-85.47%,56.63-69.70%,64.64-68.12%. To extend the turnover time of slow SOC pool is a key factors of improve the reserve of total SOC.4.The organic carbon pool size and turnover time had significant positive correlations with total soil organic carbon, calcium carbonate content, total calcium, soil pH, total nitrogen, C/N. Humus content and soil organic carbon pool and turnover time was a significant positive correlation. The activies of soil catelase and urease significantly affect soil organic carbon content and turnover time. |
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