| Since the 1980 s, China has launched a number of major ecological projects, and the implementation of these huge tasks has not only improved the ecological environment, but also has made the farmers in project area cast off poverty. However, overall quantitative research has not been carried out as to carbon stock and carbon sequestration benefits of the project, and one of the main reason is the lack of a widely accepted method of carbon sequestration for these ecological engineering. Through systematical analysis, this paper has summarized the main method of calculating carbon storage of regional scale, and on the basis that the project is divided into three categories, has proposed methodology framework for the representative engineering, and finally taking the Grain for Green Program in Jiangxi province in 2001-2009 as an example, through the use of different methods, has calculated the carbon reserve and carbon sequestration benefits. The main results are as follows:(1) Based on the characteristics and data of Grain for Green Program, as to measurement of carbon sequestration in conversion of Grain for Green Program, this paper has proposes to take means of allometric growth equation method and CASA-CENTURY model on the basis of scale in sample plot extended to regional scale; as to Natural Forest Protection Program, this paper has proposes to adopt method of confluence analysis and method of remote sensing downscaling with IPCC method/continuous function method of conversion factor combined with the inventory data and remote sensing data(China Cover); as for production area of commercial forest in the Natural Forest Protection Program, this paper has proposes to use method of CBM- CFS3 model; as for project of Returning Grazing Land to Grass Program, this paper has proposes to adopt combination method of CASA- CENTURY model.(2) Our research shows that it is impossible to use the same method on all projects because of the complexity of the project and data availability. If possible, 2 or more methods are necessary.(3) We use allometric equation method, volume to biomass methods and CBM-CFS3 model simulation method to calculate the vegetation carbon storage and use CBM-CFS3 model to calculate soil carbon storage. The results show that the allometric equation method estimates the maximum, CBM-CFS3 model estimates the smallest. CBM-CFS3 model is suitable for simulation soil carbon storage change after returning farmland to forests.(4) The vegetation carbon storage is 1.5 Tg in regions with conversion of cropland to forest calculated by four kinds of methods, which are allometric growth equation method, two kinds of volume- biomass methods and CBM- CFS3 model simulation method, soil carbon storage of 3.83 Tg calculated by CBM- CFS3 model. The vegetation carbon pool in project region has been increased 0.92 Tg, with annual average increase of 0.85Mg/hm2·a, and total carbon storage in regional conversion of cropland to forest has been increased 870129.33 Mg, with annual average increase of 0.1 Tg/a, an annual increase of 0.81 Mg/hm2·a.(5) The area of conversion of cropland to forest and of afforestation in barren hills and wastelands has accounted for 6.71% of the provincial forest area at the same period in conversion of cropland into forestland program in Jiangxi province by the end of 2009, and the average amount of carbon sink is 0.42 Tg/a in 9-year implementation of returning farmland to forest, which accounts for 0.92% of fossil fuel emissions in Jiangxi province. Along with the increase of age of forest and the improvement of afforestation measures, conversion of cropland into forestland program will exert greater benefits of carbon sink. |
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