关键词: 林业补贴, 森林生态效益, 最优砍伐决策模型, 定量分析

Abstract: To encourage afforestation and improve the social welfare,governments provide subs-i-dies to support the forestry.Different types of subsidies give different results.Some can improve the social welfare,but the others cannot.The reason is that the subsidy changes the benefit and cost cash flow during the farmers'planting process and influences the time that maximizes the net present value of the farmers,which causes the optimal harvest time delayed or ahead to the social one.In order to distinguish the different effects,this paper sets up a quantitative model for forestry management,which includes the social benefit due to carbon sequestration of forest.Then the model is employed to analyze a subsidy provided by a city government in East China to support a local forest farm.The result shows the optimal harvesting age excluding social benefits is 19 years.When including social benefits,the optimal harvesting age increases from 19 year to 31 years as the carbon price rises from 0 yuan/t to 1 000 yuan/t.The inclusion of subsidies to encourage afforestation shortens the optimal harvesting age to 11 years from the forest owner's point of view.Compared with no subsidy,the subsidy causes much more social loss,which increases from 7 750 yuan/t to 17 704 yuan/t.The reason is that the subsidy brings forward the optimal harvest time,and the farm owner will not concern the externalities of the forest.The result indicates that not only to consider the social benefit but also to maximize the net social present value is important to a reasonable forestry subsidy.

Key words: ecology benefit of forest, optimal harvest model, quantitative analysis, forestry subsidy