UBC Theses and Dissertations
Determining harvest schedules and profitability under the risk of fire disturbance Peter, Brian
This thesis demonstrates a method of determining harvest schedules based on the uncertainty of natural disturbance, and explores the interactions between disturbances and harvest scheduling. A model of wildfire occurrence is first developed, and the effects of wildfire on forest growth, landscape attributes, and harvesting are evaluated. A method to determine an appropriate harvest target is developed that considers the risk tolerance of the forest owner. The impacts of various model assumptions on estimates of sustainable timber supply are then examined through sensitivity analyses. The impacts on timber supply when natural disturbance is explicitly simulated are more complex than simple reductions to the total amount cut and may be of interest to forest managers who wish to predict the long-term, supply profile. A 'buffer' that ensures a sustainable harvest in the face of disturbance is demonstrated in terms of reduced harvest volumes and excess available timber. Sustainable harvest flows within this model are sensitive to both risk tolerance and the time span considered. Assumptions on the ability to salvage disturbed areas and the effects of disturbance suppression further complicate our choice of harvest target, and our lack of ability to constrain the largest disturbances over time may reduce harvest rates, as well as increasing the range of variation in landscape attributes. Estimates of profit from changing rates of forest harvesting provide a measure of the cost of natural disturbance, and when wildfires are suppressed, profit provides a measure of the value of suppression. On a 288,000-hectare area in northeastern BC, the cost of historical natural disturbance was estimated at $4 million per year. Suppressing 98.3% of disturbance events had a value of $1.8 million per year and increased the value of the forest by 50%. Increasing risk tolerance produced higher short-term profits on this landscape, though as buffers are drawn down over the long-term, profits increased very little, and were accompanied by periods with much lower profits.
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