关键词: 湿地松, 材脂兼用林, 最优轮伐期, 林地期望价值

Abstract:

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.

Key words: slash pine, timber and resin plantations, optimal rotation, land expect value (LEV)