| Larix kaempferi is one of important tree species in north sub-tropical area in China, where is the most appreciate area for L. kaempferi cultivation and in which it had been planted over 0.33 million ha. In this area, L. kaempferi grows fast at early ages and usually has better wood properties, and never occupies lands for agriculture with better acclimation ability and anti-disaster ability. Moreover, it had been proved that L. kaempferi is one kind of good pulping material compared with other kind of Larix because of its higher biomass yield and pulping yield, longest fiber, lowest kappa number and pulp beating energy consumption, easier controlled pulping procedure , stable properties of paper and the potential for paper-making. Therefore, L. kaempferi has broadly market prospects and it is significant to forest-pulp-paper integration as a species to short-rotation and pulping-making. However, due to relatively short introdction period of L. kaempferi in this area, the rotation problem of has not been researched. Consequently, how to harvest L. kaempferi scientifically has become a significant problem in L. kaempferi plantation management. Therefore, this paper studied the optimal rotation age of L. kaempferi by discussion of various maturity ages in order to guiding management and production in this area.The main methods and conclusion are:The Quantitative Maturity Age for L. kaempferi was studied by Growth Model method and non-linear regression technology. The results showed that Extended-Schumacher model was perfect to describe the stand stocks growth for L. kaempferi. The Quantitative Maturity Age of L. kaempferi in various site index and stand density ranged from 28-42a, and the stand with higher site index and stand density usually had older Quantitative Maturity Age.The Technology Maturity Age for L. kaempferi was discussed with synthetic judgment of pulping-making properties, fiber characters and physical strength of pulp of L. kaempferi with different age in sub-tropical area. The result indicated that Technology Maturity Age of L. kaempferi is 13-22a. Furthermore, the differences of pulping properties of L. kaempferi in various site index, stand density and different parts of the tree(upper, middle and lower parts of trunk and branch) were researched by ANOVA analysis. The results showed that there are no different between L. kaempferi of various site index and stand density, however, the pulping-properties of trunk is better than branch significantly. Moreover, the difference between different parts of trunk is not significant.The Economical Maturity Ages for L. kaempferi were analyzed by Improved-DCF method (Land expectation value, Annual net present value and Inner return of rate) and Real Options method which is advanced method at present, based on discussion of the appreciate discount rate for forestry management. The results indicated that the LEV maturity ages for L. kaempferi in site index 13,15,17,19 and 21 were 25-26a,24-26a,22-24a,20-23a,20-21a respectively; the corresponding ANPV maturity age were 24a,23-24a,21-22a,18-21a,18-19a respectively and the corresponding IRR maturity age were 26-27a,24-26a,21-24a,18-22a,17-19a respectively; Meanwhile, the RO maturity age were 25-27a,24-26a,22-23a,21-22a,19-22a respectively at the current pulpwood price level. The results also showed that the L. kaempferi plantation with higher site index or stand density (within reasonable range) usually had more profitable gain and shorter economical maturity age.Sensitivity analysis was evaluated to L. kaempferi in various site index and stand density with the changing of pulpwood price, discount rate and the cost of plantation management. It was indicated that the economical gain of pulpwood plantation would decreased with the increase of discount rate and decrease of pulpwood price and management cost; Furthermore, the most influential factor is discount rate, followed by pulpwood price and management cost.The Harvest Price Thresholds and the Shortest Rotation Age were concluded by discussing the economical maturity age of L. kaempferi with Real Options method. The Harvest Price Thresholds means the lowest wood price to harvest a plantation at a certain age, which means Harvest Option should be chosen when the wood price was higher than the price threshold at a certain age, otherwise Wait Option (deferring harvest) should be chosen. The Shortest Rotation Age means the shortest rotation age of a plantation as the wood price keeping at a high level, in other words, the Wait Option should be taken whatever the wood price is when the stand age to be smaller than the shortest rotation age. The results showed that the Harvest Price Thresholds decreased with the increasing of stand density and the Shortest Rotation Age of L. kaempferi plantation with the site index 13,15,17,19 and 21 were 22-25a,21-23a,19-21 and 17a respectively.The Integrated Decision-Making System of the optimal rotation age of L. kaempferi was established by Analytic Hierarchy Process (AHP) technique, following the concept of"Based on technology maturity, focused on economical maturity age, and take Quantitative maturity into consideration". The optimal rotation age of various L. kaempferi plantation with different site index were figured out by the weight of various factors determined by Integrated Decision-Making System, and it was indicated that the optimal rotation age of L. kaempferi plantation with site index 13 and 15 were18-19a, and the plantation with site index 17,19 and 21 were 17-18a.The Optimal Rotation Age is a complex integrated multiple-criteria problem which needs to be evaluated by various maturity criteria. Moreover, the economical maturity problem is a focus issue in forest management discussed by researchers all over the world. Furthermore, it will be the hotspot and focusing point that considering the optimal rotation age from economical maturity aspect in China, because the rich timber forest resource and the accelerating process of market. In this study, the Real Options method was the main method to cope with rotation age, as the pulpwood price fluctuation and management flexibility were taken fully account, which has provided flexible and sound management strategy and could be viewed as a preferable method to evaluate forest economical maturity age.As mentioned above, the Integrated Decision-Making system and various maturity ages of L. kaempferi concluded in this study have provided guidance approach and theoretical basis for L. kaempferi management and production in sub-tropical area in China. |
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