Research On Ecological Benefit Evaluation Of Grain For Green Project In Beiiing

Grain for green project is an important ecological construction project in China, which is also one of the ten key ecologic projects globally. It carries tremendous practical meaning for the improvement of ecological environment in the new century. The ecological benefit and value assessment of post project has also become a hotspot that draws great attention. The paper summarized and explored the evaluation method for "grain for green project" on the basis of analyzing and discussing the relevant theory. In ways of soil and water conservation, carbon sequestration and oxygen generation, atmosphere purification, biodiversity protection, and nutrient accumulation, the paper applied RS, GIS and the theories mention above, and took the grain for green project in Beijing from 2000 to2004 as an example to assess the general benefit by adopting quality and quantitative combination method as well as quantitative dominated method.It was revealed that1) Ever since the implementation of the project, the size of forest has increased by 36666.67hm2 with ecological benefit that is worth 1.9350271 billion yuan per year.2) Among the composition proportion of the general value brought about by the project, the order is:water conservation>carbon sequestration and oxygen generation>biodiversity protection>soil conservation>nutrient accumulation>air purification.3) Due to the grain for green project, the precipitation intercepted each year reachs 75.2164million ton besides reducing 37.6 thousand ton of soil erosion per year. The amount of carbon sequestration by forest biomass is 86797.48 ton and soil carbon sequestration is 15473.33 ton annually. The oxygen generated by the forest biomass reached 231371.21 ton per year. The amount of sulfur dioxide, nitric dioxide and fluoride absorbed is 4009022.58kg,21996080kg,127743.08kg respectively with 508701.37 kg of blocked dust. After the project, the increasing amount of nitrogen, phosphorus and potassium is 2590.97 ton,599.42 ton and 894.24 ton respectively.Base on the evaluation result above, the paper displayed the construction outcome of grain for green project and discussed the following development policy, which provided better and more scientific guidance for ecology construction, and made sure that the project progressed steadfastly towards the direction of improving policy, strengthening outcome, guaranteeing quality so as to further promote the validity and continuity of the project.