1. Burn Baby Burn! Prescribed Burning as a Silvicultural Method Dee Asbury & Erin Bodine Math 164: Scientific Computing 29 – April - 2003

2. Motivation History of wildfire suppression –Smokey-the-Bear Effect “Only you can prevent forest fires!” Ideology: any forest fire is BAD! –Shift of control burn Suppress wildfires Use control or prescribed burns to simulate natural forest cycles Maintenance of forest diversity –Want to maintain a balance between the various tree populations if a forest –Many tree species suffer without fire Ground litter too deep for shallow root trees Fire replenishes nutrients in top soil Seeds remain dormant, fire releases seeds from cones

3. The Questions How can prescribed burns be used to maintain forest diversity? How will forest equilibrium be affected by fire suppression? Can we find an optimal burn frequency to yield desired forest dynamics?

4. The Biology: A Hardwood and Pine Tree Forest Hardwoods – Fire Haters! –Hardwoods have a deep root system –Fire has phoenix effect on hardwoods –Spread rapidly Pine Trees – Fire Lovers! –Pine trees have a shallow root system –Fire causes pine cones to open –Pine trees have greater fire tolerance Dynamics –Hardwoods will crowd out pine trees!

5. The Model: An Overview The model uses time dependent transition matrices to calculate –annual tree populations –forest diversity The three transition matrices are –growth (G) –replacement (R) –death (D)

6. The Model: Growth Matrix Example of a growth matrix Transition matrix models four height classes

7. The Model: Replacement Vector Example of a replacement vector All replacements occur in smallest height class

8. The Model: Death Matrix Example of a death matrix Transition matrix models four height classes

9. Results: Maximum Fire Suppression

10. Results: Control Burn

12. Results: Answers to the Questions How can prescribed burns be used to maintain forest diversity? –Prescribed burns, at the appropriate frequency, can maintain the desired forest diversity. How will forest equilibrium be affected by fire suppression? –In the pine/hardwood forest frequent fires will maintain a pine forest, infrequent fires will maintain a hardwood forest. Can we find an optimal burn frequency to yield desired forest dynamics? –Close! Populations are slowly declining over time.

13. Extensions Model carrying capacities more accurately. Model effects of fire frequency on local wildlife. Model effect of fire frequency on biomass instead of tree populations. Add dynamics of shrubs and other flora. Add effects of other methods of silviculture (i.e. logging and thinning).