农户经营杉木林的碳汇供给及其影响因素

Carbon Sequestration Supply and Its Influencing Factors for Farmers Operating Fir in Chinese Southern Collective Forest Zone

基于我国南方集体林区浙江、江西、福建三省202户农户杉木林经营数据,结合已有生长模型,采用生物量转换和扩展因子法,测算了杉木林生态系统固碳量,并采用修正的Hartman模型,在林地期望价值最大化的决策目标下,估算出了碳汇价格、利率、木材价格变动对杉木林碳汇供给量的影响。结果表明:①最优轮伐期及碳汇供给量与碳汇价格成正相关,与利率、木材价格成负相关。②在碳汇价格变化情况下,最优轮伐期由大到小依次为,劣等地>中等地>优等地,相反,碳汇供给量依次为,优等地>中等地>劣等地,劣等地的最优轮伐期和碳汇供给量变动幅度要明显大于中等地和优等地。③利率在7%-8%变动时,优等地的最优轮伐期和碳汇供给量均未发生变化;利率在4%-5%变动时,中等地最优轮伐期和碳汇供给量均未发生变化;而在1%-8%的变动区间,劣等地的最优轮伐期和碳汇供给量均在不断缩短和降低。④当木材价格上升10%或下降10%时,对优等地的最优轮伐期和碳汇供给量均未产生影响;对中等地而言,仅当木材价格下降10%时,最优轮伐期和碳汇供给量均发生变动;而对劣等地而言,木材价格上升或下降都对两者产生影响。研究得出如下结论:碳汇价格、利率、木材价格对杉木林经营最优轮伐期及杉木碳汇供给量有重要影响,在碳汇价格、利率、木材价格变化情况下,不同立地条件的碳汇供给价格弹性、利率弹性、木材价格弹性存在显著差异。立地条件通过影响杉木营林成本和产出量,从而对杉木林经营的最优轮伐期及碳汇供给量产生较大影响,立地条件越差的地块对碳汇供给量越敏感,随着碳汇价格逐步上升、利率和木材价格的逐步提高,碳汇供给变化为劣等地大于中等地和优等地,而碳汇供给量为优等地大于中等地和劣等地。

Based on the Chinese fir management data of 202 households in Zhejiang, Jiangxi and Fujian provinces, we estimated the ecosystem carbon sink of Chinese fir using existing growth model and biomass conversion and expansion factor method. Then we estimated the influence of its carbon sink supply under different carbon prices, interest rates and timber prices, with the maximization of land expected value and the modified Hartnmn model. The result shows that ： the optimal rotation age and supply of carbon sink have a positive relationship with carbon price, but has a negative relationship with interest rates and timber price. When the carbon price changes, the optimal rotation age of different site conditions in descending order are inferior land, medium land and excellen land; on the contrary, the supply of carbon sink in descending order are excellent land, medium land and inferiol land. The change of optimal rotation age and carbon sink inferior land is larger than that of medimn land and excellent land. When the interest rate changes from 7% to 8%, the optimal rotation age and supply of carbon sink of excellent land remain the same, but the medium land changes when the interse rate changes from 4% to 5%, and the inferior land changes when the interest rate changes from l%to 8%. When the timber price riss by 10% or decreases by 10%, none of the optimal rotation age and supply of carbon sink changes, and for medium land, the changes happen when the timber price decreases by 10%, but for inferior land the changes happen when the timber price rises or decreases. The conclusions are as follows： the carbon sink prices, interest rates, timber prices all have important impacts on the optimal rotation age and supply of carbon sink. There are significant differences with site conditions among elasticity of carbon sink price, elasticity of imerest rate and elasticity of timber price when they change. The site conditions have an important impact on the optimal rotation age and supply of carbon sink by affecting silvicultural costs and volume of output. The worse the site condition, the more sensitive elasticity of carbon sink, supply. As the price of carbon sink, interest rates and the price of timber gradually rises, the carbon sink change of inferior land is greater than that of medium land and excellent land, but the amount of excellent land is greater than that of medium land and inferior land.