Spatial Forest Harvest Scheduling for Areas Involving Carbon and Timber Management Goals

Forest carbon sequestration has become an important ecological service for human society. Given the widespread attention paid to global climate change over the last few decades, a potential need has arisen to develop forest management plans that integrate carbon management and other spatial and non-spatial goals. The objective of this research was to develop a spatial forest planning process by which one could assess either a carbon stocks objective, a timber production objective, or a spatial objective related to the arrangement of forest management activities. This process was used to evaluate the maximization of (1) volume scheduled for harvest; (2) carbon stocks; and (3) spatial aggregation of the management activities through a utility function where all are equally weighted objectives. The process was employed for the development of 30-year plans for a forested landscape in northeast China that was approximately 120,000 ha in size. In addition, the sensitivity of the results with respect to four initial forest age structures was tested. Constraints mainly included those related to the need for an even flow of scheduled harvest volume and to the need to adhere to a maximum harvest opening size. The proposed scheduling process employed a simulated annealing algorithm to schedule harvests in an attempt to produce a high value of the utility function. Results showed that carbon stocks in the case study forests could significantly increase in the next 30 years under the proposed harvesting plans. Of the case study forest landscapes, the values of both the utility function and the computing time required were significantly different between different initial forest age structures (p < 0.05), i.e., the older forest landscape obtained the highest average solution value (0.6594 +/- 0.0013) with the fastest processing speed (2.45 min per solution). For a fixed harvest level, the average carbon density (tons per hectare) at the end of planning horizon also increased by 4.48 +/- 9.61 t/ha, 8.73 +/- 10.85 t/ha, 2.99 +/- 9.19 t/ha and 1.03 +/- 9.77 t/ha when maximizing the total utility functions for the actual, young, normal and older forests, respectively, when compared those at their initial conditions. This heuristic spatial forest planning process can allow forest managers to examine a number of different management activities, for both timber production and carbon stocks, prior to selecting a preferred alternative.