不同的林业补贴产生不同的效果:可能提高社会福利,也可能降低社会福利。出现这种差别的原因是补贴使林业生产收益流发生了变化,从而使得林业生产收益最大净现值到来的时间相对于社会最优时间提前或延后。论文建立了一个以林木吸收碳来衡量森林生态效益的林业生产收益定量模型,并通过该模型对华东某市的一项林场补贴政策进行分析。分析结果是,在没有补贴的情况下,该林场最优砍伐时间为第19年,当存在补贴的情况下,林场的最优砍伐时间提前到第11年,而随着碳价格从0增加至1000元/t,社会最优砍伐时间从第19年增加到第31年,造成的社会净损失从7750元/hm²增加到17704元/hm²。鉴于此,合理的林业补贴要能够促使私人效益与社会效益相统一。

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.