Watershed

1. MONTANA BITTERROOT NATIONAL FOREST IDAHO Modeling Impacts of Potential Climate Change and Associated Wildfire Occurrences on the Levels of Sustainable Resources Jimmie D. Chew, jchew@fs.fed.us Christine Stalling, cstalling@fs.fed.us Barry Bollenbacher, bbollenbacher@fs.fed.us Rocky Mtn Research Station Rocky Mtn Research Station Northern Region Potential Old Growth Conditions Wildfire Abstract The potential impacts of changing climate on sustainable natural resource goals is examined in the context of a National Forest over a 300 year planning horizon using a spatially explicit, stochastic, landscape level simulation model. Spatial and temporal changes are simulated using data representing a National Forest located in the Northern Rocky Mountains to examine the influence of wildfire, insect and disease activities as they occur at various levels resulting from warm and dry climate cycles and higher probabilities of extreme fire events over a planning period. Differences in the long term sustained yield for wood products, acres that have the potential to provide old growth conditions, the frequency of wildfire with significant impacts on water quality, and the acres of wildfire in a wildland-urban interface are compared. Fuel reduction treatments are examined at 2 levels for the scenario with the highest occurrence of wildfire over the planning period. • Simulated fire levels resulting from climate scenarios representative of the 1950s – 1990s were comparable to actual fire events that occurred between 1879 and 2002. • Addition of warm and dry cycles every 4th decade resulted in a minor increase in fire levels. • Increased probabilities of fire events under extreme wind conditions resulted in significant increases in the total acres burned. • The current and increased levels of treatments reduced total acres burned, but not to the historic level. • Increased levels of fire resulted in a significant reduction in the percent of plant communities with potential as old growth on the Forest. • Treatment scenarios resulted in minor gains in potential old growth communities. • Potential old growth plant communities were considered to be those that had a • quadratic mean diameter of 15 inches or greater. Insect and Disease Watershed No Treatments The Model The Forest Current treatments SIMulating Patterns and Processes at Landscape scaLEs Increased treatments • Potential for watershed damage was based on 300 year simulations. • Damaged watersheds were those with more than ten percent of their area impacted by stand replacing fire. Total decades of stand replacing fire occurring on more than 10 percent of drainage Increased fire resulted in reduced levels of insect and disease activity. Insect and disease levels increased when treatments reduced levels of fire on the Forest. http://www.fs.fed.us/rm/missoula/4151/SIMPPLLE Wildland Urban Interface Long Term Sustained Yield The Simulation Scenarios • Climate representing conditions of the 1950s – 1990s and a 2 percent probability of extreme fire events. • Five sets of simulations were run with warm, dry cycles every fourth decade. • The probability of an extreme fire event occurring along with the warm and dry cycles were set at 2, 5, and 10 percent. • Two sets of simulations were run with treatments, warm, dry cycles, and a 10% probability of extreme fire. • Increased fire resulted in a reduction of long term sustained yield. • Reduction of fire through treatments increased the long term sustained yield. • Harvest levels were set at 1% per year of the 15 inch DBH and larger size classes on land allocated for forest production. • Fuel reduction treatments were applied to polygons with probabilities of stand replacing fire greater than zero following 300 year simulations. • Comparison of treated to non-treated scenarios showed a reduction in fire due to treatments but little difference between the 2 treatment scenarios. Poster Presenter, Elizabeth Bella Ecologist, Seward Ranger District, Chugach NF