Evaluation Of Ecological Benefit Of Returning Farmland To Forest Project In Three Provinces In Northeast Of China

This study was focused on the project of returning farmland to forest in northeast area in China, based on long-term ecological monitoring of forest ecosystem and dynamic data of forest resource. We researched the evaluation index system and method of the engineering of forestry ecological benefits, and evaluated quantitatively the ecological benefits of forest vegetation in water conservation, soil conservation, carbon sequestration and oxygen liberation, nutrients accumulation, atmosphere environment decontamination and biodiversity protection, so as to evaluate the ecological benefits of returning farmland to forest in northeast three provinces comprehensively, provide scientific basises for evaluations of the implementation effects of the national engineering of forestry ecological and the changes of policy, also provide technical guidance and data support for the engineering of the forestry ecological in future.The results show that:1)Compared with the wasteland in different soil depths: the Bin County of Heilongjiang province returned forest soil bulk density decreased by 9.56%～13.44%,soil porosity increased by 6.33%～23.94%; The Da’an County of Jilin province returned forest soil bulk density decreased by 8.17%～24.75%,soil porosity increased by 6.33%～23.94%.Therefore, Bin county and Da’an county returned forest can improve soil physical properties effectively;2)Compared with the wasteland in different soil depths: the Bin County of Heilongjiang province returned forest soil available nitrogen content increased by 7.52%～24.62% and available phosphorus content increased 2.55%～34.24%, available potassium content increased 32.56%～64.06%. The content of available nitrogen in the soil increased by 36.47%～96.86%, the content of available phosphorus increased by 23.11%～50.9%, the content of available potassium increased by 50.69%-81%;3)The Bin county of Heilongjiang Province returned forest soil erosion resistance has been significantly improved, and in the slope of 15 degrees, it increased most significant, which proves returned forest can curb the occurrence of soil erosion effectively. 4)It can be obtained after calculation that the project of returning farmland to forest for 14 years has conserve 20.8 billion cubic meters,3.6 billion carbon,1.37 million tons of N, P, K, sixty-five million soil, 2.35billion tons of nutrients in vegetation,2.78 billion tons of atmospheric pollutant.