| The Grain for Green Project(GGP) as a major Chinese forestry ecological engineering has been conducted 15 years from1999 with tentative experiments to 2014. The second stage of GGP was initiated after 2014. The project significantly achieved restoration and improvement the ecological environment in the middle west of China, especially the regions containing the upper and middle reaches of China’s Yangtze and Yellow River. After the project implementation, the forest area increased significantly and the arable land was protected effectively. The project improved the food production and farmers’ income, accelerated economic restructuring and promoted the overall development of social, economic and ecological benefits. The regions containing the upper and middle reaches of China’s Yangtze and Yellow River were not only Chinese important ecological function areas, but also key areas of GGP implementation and monitoring ecological benefits. The study of ecological benefits on GGP in the region, will provide important science and technology support for the new round of GGP implementation.This study coupled Grain for Green Project data of resources area by the end of 2013, ecological benefits monitoring stations of the project in the study area, position observation station of the forest ecosystem, the long-term observation data of other auxiliary observation sites and social public data released by authorities or institutions. We used the technology of continuous observation, inventory of a complete index system of forest ecosystem services and established distributed calculation model based on 7 indicators, included water conservation, soil conservation to evaluated and analyzed the physical accounts and value of ecological benefits of GGP in provinces and regions containing the upper and middle reaches of China’s Yangtze and Yellow River. Furtherly, this paper explored the theoretical method of valuing physical accounts in the forest ecosystem services assessment and the conversion rate from forest ecosystem functions to ecosystem services. We identified the correlation of influence factors for the ecological benefits of GGP in the study area used data envelopment analysis, size analysis and grey relational analysis model. Main conclusions were as follows:(1) Ecological benefits physical accounts from GGP in provinces containing the upper and middle reaches of China’s Yangtze and Yellow River: the quality of water conservation, solid soil, protecting fertilizer, carbon accumulation, trees release oxygen nutrients, providing air negative ions, absorbing pollutants, absorbing dust and windbreak and sand-fixation were respectively 0.731 billion m3/a, 447 million t/a, 15.2432 million t /a, 34.4854 million t/a, 81.7571 million t/a, 794200 t/a, 6.62 × 1025 /a, 2.4833 million t/a, 322 million t/a, 179 million t/a. Those valuing physical accounts(present price in 2014): the total value of ecological benefits from GGP in the study area was 1.00715 trillion Yuan/a. Water conservation, soil conservation, carbon sequestration, trees release oxygen to accumulate nutrients, purifying atmospheric environment, biodiversity conservation and forest protection were respectively 68.028 billion Yuan/a, 94.176 billion Yuan/a, 156.021 billion Yuan/a, 14.336 billion Yuan/a, 191.977 billion Yuan/a, 144.487 billion Yuan/a and 38.125 billion Yuan/a.(2) The principle of Equivalent substitution and Equivalent weight balance was enough important to advocate in valuing physical accounts in the forest ecosystem services. The principle brought the forest services’ proportions into correspondence with the practical forest situation by keeping balance among many price parameters with consideration to not only the theories of economics and commodity markets but also the principle and process of ecosystem services.(3)Taking air particulate matters absorption of plantation ecosystem to a case, this paper discussed the conversion rate of forest ecosystem function to this service. The ability to absorb particulate matters of different tree species had no connection to the conversion rate of the functions to services. Cedrus deodara and Taxus cuspidata Sieb had the highest conversion rates, respectively, which were 95% and 85%, Pinus bungeana and Platycladus orientalis had the lowest conversion rates, which were 47% and 48%. The conversion rate of plantation ecosystem absorbing air particulate matter function to the service in heavily air pollution area was high. And the conversion rate of the cities with fine air superiority and lower content of particulate matters was relatively low. It was mainly due to the blade microstructure features.(4) The afforestation brought the ecological benefits of soil and water conservation through the ground and underground structures. Protecting fertilizer efficiency was related to soil condition in engineering area, and was closely affected by surface vegetation coverage, vegetation type, slope, soil type and other factors. The ability of carbon sequestration and releasing oxygen depended on tree species and forest category, plantation age, and so on. The ecological benefit of trees accumulating nutrients was closely related to forest net primary productivity, which associated with hydrothermal conditions and tree species composition. The ecological benefit of purifying atmospheric environmental was closely related to leaf area of vegetation, canopy structure, leaf table fur, chemical composition and leaf waxy structure. The leaf of broad leaf tree species with a rough surface structure had a better effect on capturing and entrap particles. Trees in sandstorm regions played a significant role on ecological benefit by lowering wind speed, weakening the wind, fixing sand and preventing from wind erosion.(5) The results of input and output envelopment of model analysis of GGP data showed that all of the provinces in the study area are effective on technology and scale. The size of its policy guidance and adjusting the direction were certainly scientific, and had less component of blindness. Soil and water conservation benefits(including conserving water and soil conservation) in the study area played a leading role on forest ecosystem services. Carbon sequestration and nutrient accumulation, purifying the atmosphere environment and biodiversity protection services to background environment, hydrothermal conditions, and tree species selection of returning farmland area ware associated. It had the regional characteristic. Farmland returning to woodland category selection and forest tending, should be targeted to increase technical efficiency and scale efficiency, and then improved the ecological benefit value of GGP.(6) We made effort to located the direct and indirect effect of various factors which impacted GGP using path analysis model. The results showed forest ecological benefits of GGP in the study area, had a very significant positive correlation with returning farmland to forest and project investment amount, and had a significant positive correlation with area of engineering resources, waste hills or un-reclaimed lands which were suitable for afforestation and ecological forest resources. The investment amount of GGP had the biggest directly effects to the project ecological benefits in the study area. Its direct path coefficient was 2.9074.The resource area of the project and three vegetation recovery types significantly influenced the indirect effects of the project ecological benefits. Their indirect path coefficients respectively were 4.5470, 5.0123, 5.0592 and 4.1461.The investment amount of GGP, returning farmland to forest, resources area of the project and ecological forest, and the interaction between them as dominant factors, jointly controlled the intensity and direction of the conversion process. |
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