湿地松材脂兼用林最优轮伐期的经济分析--以江西省景德镇市枫树山林场为例

Economic Analysis on Optimal Rotation Period of Slash Pine Plantations Used for Timber and Resin—A Case Study in A State-Owned Fengshushan Forestry Farm of Jingdezhen,Jiangxi Province

【目的】我国湿地松材脂兼用林的轮伐期是在用材林数量成熟龄的基础上适当延长得到的。虽然该轮伐期可以取得一定的经济效益,但能否获得最优的经济效益尚缺乏科学依据。本研究通过分析湿地松经营中木材和松脂对经济绩效的贡献,确定采脂和采伐的时间节点及其影响因素,为保证湿地松人工林经营效益的最大化和林产品生产的可持续性提供科学依据。【方法】基于江西省景德镇市枫树山林场湿地松人工林生产实践,构建考虑木材和松脂两类产出的Faustmann模型,计算林地期望价值(LEV)。然后:1)通过比较材脂兼用林和用材林的收入现金流,阐明木材和松脂在湿地松人工林收入中的贡献;2)在不同折现率下,对湿地松两类人工林的LEV和最优轮伐期(T*)进行比较;3)设置活立木价格、松脂价格和林分经营成本的变化范围,评估在不同折现率下,LEV和T*对这些影响因素变化的敏感性。【结果】1)经营材脂兼用林的名义现金收入较高,但如果经营时间足够长,湿地松用材林和材脂兼用林的名义现金收入将趋同。虽然松脂收入提高了林分的LEV,但是,木材收入对总的名义收入的贡献将影响LEV的变化。2)湿地松材脂兼用林的T*比用材林的T*长。若其他条件不变,折现率增加,用材林的T*缩短,但材脂兼用林的T*略微延长。3)活立木价格对湿地松用材林的LEV和T*有正向影响,但在木材价格下降时对材脂兼用林T*的影响不明显。松脂价格对材脂兼用林的LEV有正向影响,但对T*的影响不明显,只在高折现率时,价格下降,T*下降。人工成本对湿地松用材林T*有正向影响,对材脂兼用林的T*没有影响。【结论】1)湿地松材脂兼用林比用材林具有更强的创收能力。木材收入对材脂兼用林总收入的贡献是不可忽视的。湿地松人工林经营要以木材和松脂收入总额最大化为目标,采脂的同时要兼顾木材的生长。2)对湿地松人工林进行采脂确实延长了T*。但在当前的价格水平下,如果折现率超过10%,人工林经营将无利可图。因此,低折现率有利于松脂的长期生产。3)材脂兼用林的T*对松脂价格、人工成本和较低木材价格时的变化反应不敏感。从投资的角度看,湿地松人工林的盈利能力主要取决于折现率。折现率对材脂兼用林T*的影响与木材收入占林分总收入的比重有关,比重越高,折现率对T*的负向影响就越大。4)采脂起始时间的确定会影响LEV和T*,当林分接近成熟时松脂形成较多,采脂对林分生长的影响逐渐减弱,最为合适的采脂起始年龄。

【Objective】The rotation period of slash pine timber and resin plantations in China is appropriately extended on the basis of the mature age of timber plantations.Although certain economic benefits can be obtained in this rotation,there is still no scientific basis for whether the optimal economic benefits can be obtained.By analyzing the contribution of timber and pine resin to the economic performance of slash pine management,this study determined the time timeline of resin tapping and forest harvesting and the influencing factors,which can provide a scientific basis for maximizing the management benefit of slash pine plantations and the sustainability of forest product production.【Method】Based on the production practice of slash pine plantations in Fengshushan forestry farm of Jingdezhen,Jiangxi Province,a Faustmann model was established to calculate the land expected value(LEV)in considering the yield of resin and output of timber.Then 1)the contribution of timber and resin to the income of slash pine plantations was clarified by comparing the income cash flow of timber and resin mixed use plantations and timber plantations;2)The LEV and optimal rotation period(T*)of the two types of slash pine plantations were compared under 4 different discount rates;3)The sensitivity of LEV and T*to the changes of these factors under the different discount rates was evaluated by setting the change range of the prices of timber,resin and operating costs.【Result】1)The nominal cash income of timber and resin plantations is higher,but if the management period is long enough,the nominal cash income of slash pine timber plantations and timber and resin plantations will converge.Although the resin income increased the LEV of stand,the contribution of timber income to the total nominal income will affect the change of LEV.2)The T*of timber and resin plantations is longer than that of timber plantations.If other conditions remain unchanged,the T*of timber plantations will be shortened with the increase of discount rate,but the T*of timber and resin plantations will be slightly prolonged.3)The price of timber has a positive effect on LEV and T*of slash pine timber plantations,but it has no obvious effect on T*of timber and resin plantations when the price of timber decreases.The price of resin has a positive effect on the LEV of timber and resin plantations,but the effect on T*is not obvious.Only when the discount rate is high,the price decreases and T*decreases.Labor cost has a positive effect on T*of timber plantations,but has no effect on T*of timber and resin plantations.【Conclusion】1)Slash pine timber and resin plantations have stronger income generating capacity than timber plantations.The contribution of timber income to the total income of timber and resin plantations cannot be ignored.The management of slash pine plantations should aim at maximizing the total income of timber and resin,at the same time,the growth of trees should be considered.2)The resin harvesting does prolong the T*of slash pine plantations.However,under the current price level,if the discount rate exceeds 10%,forest management will be unprofitable.Therefore,low discount rate is beneficial to the long-term production of resin.3)T*of timber and resin plantations is not sensitive to the change of resin price,labor cost and lower timber price.From the perspective of investment,the profitability of slash pine plantations mainly depends on the discount rate.The effect of discount rate on T*is related to the proportion of timber income in total stand income.The higher the proportion is,the greater the negative effect of discount rate on T*is.4)The determination of the starting time of resin tapping will affect LEV and T*and the most appropriate time is when the stand is close to maturity.By then more resin is formed,and the effect of resin tapping on stand growth is gradually weakened.