Spatially Explicit Optimization Of Forest Management Strategy Based On The Tradeoff Between Timber Production And Carbon Sequestration

Forests provide a wide range of products and ecosystem services for humans,which are closely related to human well-being and sustainable development.In recent years,as public understanding of forest ecosystem services enhanced,the demands on forests also diversified.Forest management is shifting from single-objective management focused on timber production to multi-objective management focused on meeting the needs of multiple ecosystem services.However,to achieve a balance among various objectives,there is a need to determine the corresponding optimal management measures according to the response of different forest stands or landscapes to different ecosystem services.This requires a more refined planning method of forest management in time and space.In addition,carbon sequestration is of particular interest as China has proposed targets of emission peak and carbon neutrality.Forest farms are the main body of forest management at landscape-scale in China,which have long sought for the ways to jointly maximize timber production and other ecosystem services.It becomes a challenge for forest management planning to rationalize management measures that can achieve a balance between timber production and carbon sequestration.In this study,a spatially explicit forest multi-objective planning model with simulated annealing algorithm as the core was developed by taking a typical state-owned forest farm in the south(Paiyashan forest farm in Jing County,Hunan Province)as the case,and using the forest survey data in 2019.The model was coded in Python and linked to GIS.In the model,forest classification management and the adjustment of the plantation age structure to the normal distribution were main constraints.We obtained the spatial and temporal allocation schemes of clear cutting and selective cutting measures at the level of forest management units during the planning horizon,achieved the objective of age structure adjustment of plantation forests.The effects of social preferences and market prices on optimal forest management were also quantified and analyzed.The main results are as follows:(1)Due to the constraints of classification management and age structure adjustment of plantation forests,the harvesting intensity of each optimized scenario was higher than that of the no cutting scenario in the first 30 years,and the existing forest volume and existing carbon stock of each optimized scenario were gradually better than those of the no cutting scenario from the 30th year onward.(2)Representing possible social preferences by assigning different weights to the net present value of timber and carbon sequestration.As the net present value(NPV)weight of timber increased,the proportion of both selective cutting and clear cutting increased.Among all scenarios,T100C0 had the highest proportion of the total area under selective and clear cutting,and TOC 100 had the lowest proportion.In terms of age structure adjustment,the optimized scenarios all adjusted the fir plantation forest to an even distribution of age class 1-6 within the first 50 years of the planning horizon,with the area of each target age class being about 1/6 of the total area of the Chinese fir plantation forest(320.8 ha),and the Masson pine plantation forest to an even distribution of age class 1-4,with the area of each target age class being about 1/4 of the total area of the timber forest of Masson pine(160 ha).(3)Among the different social preference scenarios,the scenario with the highest carbon sequestration weight,TOC 100,had better existing volume than the other optimized scenarios since 35th year,which was higher by about 8.6 × 104m3,and the existing carbon stock was better than the other optimized scenarios from 25th year,which was higher by about 4.7 × 104 t.The differences in harvesting intensity and forest existing resource dynamics among the other optimized scenarios with non-zero weight of timber NPV were small.(4)As the price of timber increases,the intensity of forest harvesting increases and the amount of existing forest volume and carbon stock decrease.When the carbon price was fixed at a medium and high price,changing the price of timber had a small impact on forest management.When the price of timber fixed at a low price,changing the price of carbon had greater impact on forest management.Fixed the price of timber at a medium and high price,changing the price of carbon had less impact on forest management.In summary,this study aimed at the synergy and trade-off between timber production and carbon sequestration,combined simulated annealing algorithms with GIS in constructing a forest planning model to obtain the optimal spatial configuration plan of forest management measures,while considering the adjustment of forest management schemes under social preference and market price scenarios.The results provide technical support for forest management and its adaptation to market regulation in the context of ecological construction,and have great significance for the policy formulation of forest quality improvement and carbon management.