The role of strategic planning in the management of fire-prone western Oregon forests for maximizing terrestrial carbon stocks over a 100-year horizon

Graduation date: 2011Current frameworks for analyzing forest carbon offset projects in disturbance-prone western forests often fail to address the dynamic nature of carbon pathways through time. They do not account for the probability of loss due to wildfire, which can influence the prediction of carbon storage at the end of a planning horizon. In such an environment, optimal treatment regimes over time are dependent on the decisions that affect carbon storage during the analysis period. Silvicultural regimes that include both pyrogenic and biogenic emissions from forests, as well as the storage in wood products, were modeled to demonstrate a method to maximize carbon storage.\ud Stand-level optimization is suggested as a method for demonstrating the development of treatment regimes to enable a full range of carbon storage benefits. These include a reduction in the risk of catastrophic wildfire, increased terrestrial carbon density, and the offset of treatment costs. This methodology may also provide a baseline for a full accounting of forestry carbon offset projects.\ud A model was developed to determine optimal management regimes that maximize the expected value of terrestrial carbon storage for three Douglas-fir (Pseudotsuga menziessi) dominant forests in western Oregon. Carbon storage values for treatment combinations were weighted by the probability of fire occurrence and the loss of carbon due to fire. The model employs probabilistic dynamic programming to determine the optimal timing and intensity of silvicultural treatments by way of thinning-from-below. Also determined are location-dependent management regimes that maximize aboveground carbon storage with fire-suppression efforts. The stand location in respect to roads is examined, specifically in terms of the effect that access distance and slope position have on the optimal timing and intensity of fuel treatments and silvicultural activities. Optimal regimes are determined for a range of forest stands, varying by stand distance-to-road and the slope location of the road above or below the stand.\ud Results suggest that a combination of let-grow and low-level density-reduction thinnings can store more aboveground terrestrial carbon in forests and long-lived wood products than grow-only control scenarios when fire is also present and fire-related emissions are accounted for. Additional expected carbon storage of optimal solutions compared to the 100-year gain for control scenarios ranged from 0 to 46%. This suggests that strategic planning by the optimization model can compete with the hedge method of the Voluntary Carbon Standard risk management, which employs carbon buffer pools to compensate for the risk associated with disturbance and can require the size of the buffer deposit to range from 10 to 60% of the generated carbon credits, depending on the risk class determined for a given project.\ud Results also suggest that both stand location and fire suppression efforts did not impact the maximization of aboveground terrestrial carbon storage in forests and long-lived wood products under moderate fire conditions (21 km hr⁻¹ 6-meter wind speed, 31° C air temperature, 40% herbaceous and 70% woody fuel moisture). However, it was shown that stand slope position relative to access roads did impact fire suppression efforts by affecting the response time and the type of suppression effort (e.g., head attack or rear attack). It is hypothesized that both stand location and fire suppression efforts would impact the maximization of aboveground terrestrial carbon in forests and wood products under more severe weather conditions, on steeper slopes, and over larger stand areas