Simulation On Effect Of Tree Species Allocation On Multiple Functions Of Forests And Its Comprehensive Benefits Evaluation

Forest and forestry have been developing rapidly in China meanwhile there has been great success in forest ecological construction.However,even though the forest resources have been continuously increasing,there are still serious problems in reality such as low productivity of forestland,few forests available for timber harvest and gap between wood supply and demand.China is facing the challenge of fulfilling the increasing demand from the society on multiple functions of forests.It is needed to know how tree species selection and allocation affect the multiple functions of forests,which is extremely useful to solve the problems of balancing the economic and ecological benefits,and the long-term and short-term incomes from the very beginning considering the long period of forest growth,thus maintaining the long-term ecological stability of forest ecosystem meanwhile satisfying better the social needs.This study selected the two tree species including Pinus massoniana(conifers)and Castanopsis hystrix(broadleaves)in the Fubo Forest Farm,the Experimental center of Tropical Forestry of the Chinese Academy of Forestry(CAF)located in Pingxiang City,Guangxi.Five tree allocations of the two species were analyzed,including normal planted forest of Pinus massoniana(M1-1),dense planted forest of Pinus massoniana(M1-2),planted forest of Castanopsis hystrix(M2),mixed even-aged planted forest of Pinus massoniana-Castanopsis hystrix(M3)and mixed uneven-aged plantation forests of Pinus massoniana-Castanopsis hystrix plantation(M4),to compare the effects of the various allocation models on timber production,carbon sequestration,biodiversity and its economic efficiency.Field investigations of the sampling stands were conducted.The PICUS model was applied to simulated and predict the forest growth and productivity of timber and carbon for 50 years.The indicators like net present value(NPV)and internal rate of return(IRR)were used to analyze the economic efficiency of different allocation models.The sensitivity of the major factors like discount rate,timber price and harvesting cost on the economic efficiency was also analyzed.And finally made a comprehensive evaluation of forest ecology function and economic benefit under five tree allocations.The results of this study showed that:(1)In terms of natural regeneration capacity,the mixed even-aged planted forest was the strongest,followed by the pure stands of Castanopsis hystrix and the mixed uneven-aged stands,and the pure planted forest of Pinus massoniana were the worst.In terms of undercanopy biodiversity,this study considered mainly the species diversity.The pure planted forest of Pinus massoniana had the richest species diversity,followed by the mixed planted forest of Castanopsis hystrix and Pinus massoniana,while the worst was the pure planted forest of Castanopsis hystrix.Between the mixed planted forests,the even-aged mixed stands were richer than the uneven-aged ones.(2)The timber yield and carbon storage are apparently different under various allocation models.As for timber yield,M1-2(13.41 m3/ha/a)>M4(13.21 m3/ha/a)>M1-1(13.11 m3/ha/a)>M3(8.00 m3/ha/a)> M2(6.83 m3/ha/a),while for carbon storage,M4(2438.12 kg/ha/a)>M1-1(1624.62 kg/ha/a)>M1-2(1581.94 kg/ha/a)> M3(1490.81 kg/ha/a)> M2(1049.62 kg/ha/a).(3)Within the 50 years of simulation period,the NPV of five tree allocation models ranked as: M3(106697 yuan/ha)> M2(103044 yuan/ha)> M3(96285 yuan/ha)> M1-2(91261 yuan/ha)> M1-1(88952 yuan/ha).The internal rate of return of the five models were all higher than the opportunity cost of the proposed funds.(4)As for the sensitivity,the NPV would increase by 1.41% with the timber price increasing by 1%,and 0.27% with the cutting cost decreasing by 1%.The decreasing of discount rate would cause an exponential growth of the NPV.The lower the discount rate,the more sensitive NPV.For the different tree allocation models,M4 was the most sensitive to the change of timber price;M1-1 was the most sensitive to the change of cutting cost;M2 and M3 were medial to the change of the timber price and cutting cost.M1-1 was the most sensitive to the discount rate while M3 was the least sensitive to it.In conclusion,the even-aged mixed planted forest of Pinus massoniana and Castanopsis hystrix had the potential of providing more economic and ecological benefits in an integrated way,which makes this model of tree allocation more propagable.