Sensitivity Analysis on Long-Term Fiber Supply Simulations in Georgia

Abstract

We used long-term simulation analysis in a spatially explicit forest management model called OPTIONS to investigate the impact of the rotation age, intensive management practices, and harvesting limits on wood production, harvesting opportunities, and long-term resource sustainability. The initial forest inventory is compiled from data sets of the US Forest Service Forest Inventory Analysis Unit, various GIS data, Landsat 5 Thematic Mapper imagery, and simplified assumptions about the spatial distribution of different forest cover types. We determined the parameters of the model from published and unpublished literature and from interviews with experts in the area of forest management in the southeastern United States. The sensitivity analyses reveal the impacts of the individual factors of the rotation age, intensive management practices, and harvesting limits and of the interaction of these factors on the sustainability of the forest resources. The results of the analyses suggest that the current timberland in Georgia can easily sustain the current level of harvesting with the current level of intensive management practices for different choices of the rotation ages. The volume available for harvesting would increase with an increasing rate of transition to intensively managed plantations (IMPs) regardless of the level of harvesting limits and rotation age. To ensure sustainability of forest resources under an increasing harvest scenario, part of new plantations would be required to convert to intensive management. The higher the harvesting limit, the more intensively managed plantations needed. The patterns of the changes in the volume available for harvesting by species groups were different for cases of keeping current harvesting limits and IMP levels versus applying increasing harvesting limits and an increasing transition rate to IMPs. Harvestable volumes are significantly different among each level of the three analyzed factors: transition rate to IMPs, rotation age, and harvesting limits. The study informs land use and policy decisionmakers about potential sensitivities of Georgia forest resource productivities to changes in forest practices-related rules and regulations.

Spatially Explicit Biomass Supply Sustainability Analysis for Bioenergy Mill Siting in Georgia, USA

“…Based on a methodology framework for analysis of various management practices and regulatory constraints and their impacts on resource and harvesting sustainability [13,14,27] investigated the impact of the rotation age, intensive management practices, and harvesting limits on wood production, harvesting opportunities, and long-term resource sustainability via long-term simulation analysis in a spatially explicit estate management simulation software called OPTIONS.…”

“…Finally, the harvesting priority by cut type and species groups was defined. The detailed definition and model inputs were described in [13,14] and [27]. Based on the ages, heights, and corresponding site index values in the FIA database, five site index classes (base age 50) were assigned to different stands:…”

“…Since even the short rotation age of the IMP in a high-site-index stand is larger than 20 years, and the goal is to find SHL by year 2020, which is less than one rotation period, for each procurement area with four different radii, the assumption of a constant IMP proportion would be reasonable. If the goal is to find SHL for a long period of time, say by year 2050, an appropriate set of transition rates to IMP should be considered in the scenarios (see [13,14] for the detail).…”

“…[27] describes analysis of long-term wood production sustainability in Georgia at the state scale, while different aspects of related studies consider various ecological aspects of current forest management practices in the state including: analysis of green-up and adjacency constraints (e.g., [54]), assessment of the impacts of stream management zones and road beautifying buffers on forest inventory in Georgia [55,56], and impacts of intensive management practices on the outcomes of these long-term simulations for Georgia (e.g., [24, and 13]. General sensitivity analysis of the considered simulations (e.g., [14,57]) were also conducted.…”

“…In the face of urban expansion and environmental pressure to reduce the numbers of acres dedicated to plantation forestry, the dramatic increase in production of intensively managed plantations may well be the solution allowing us to maintain sufficient forest biomass supplies to meet the growing demand of modern societies. Indeed, some projections have indicated that intensive pine plantation management could lead to sustainable or even increased future wood production despite a decline in the forestland base [12][13][14].…”