Addressing Wildfire Hazard in Mount Spokane State Park

Abstract

As the climate warms, extreme disturbance events are demarcating a new normal which is apparent when looking at the change in fire regimes from historical conditions. With the prevalence of wildfire across the West, land managers like the Washington State Parks and Recreation Commission (WSPRC) are concerned about the implications this new normal brings to the table. Mt. Spokane State Park, one of the largest under their jurisdiction, is a park of concern for wildfire not only because of its size and location, but its diversity in forests and human usage. Over the course of two summer field seasons, 151 plots were established across the park to address the historical context, current risk and future implications wildfire brings to Mt. Spokane State Park. To question: (1) What is the historical context of fire in the area and what past fire events have happened in and around the park?; (2) What does the park look like on the ground currently?; and (3) How would that change over time under different fire and management scenarios? To answer these questions site, ground fuel, tree, and tree core data were collected at every plot when able to be used with a family of forest simulator models developed by the USFS, the Forest Vegetation Simulator otherwise known as FVS with the Fire and Fuel Extension (FFE-FVS). With FVS, simulations were run on plot data both individually and in USNVC groupings to look at what would happen when you do or do not add fire to two different approaches, do nothing or do something with a management prescription over the course of 60 years on potential wildfire. Through analysis of structural, fuel, and fire outputs of interest over time as well as literature research and tree cores, presence of past fire activities, areas of high fire hazard and treatment effectiveness were identified. Of the 62 tree cores harvested across the park, only four had fire scars indicating the park has had small fire events in the last 100 years, but due to thorough past harvesting, determining historical fire conditions through just this methodology was not possible. The plots belonging to USNVC grouping, Northern Rocky Mountain Mesic Montane Mixed Conifer Forest, are of priority for management treatments due to high flame lengths and higher potential for crown fires. This grouping was also statistically different in many of the FVS outputs of interest when compared to the other groupings. Simulated thinning and slash treatments can reduce the probability of active crown fires, especially after removing at least 40% of the basal areas of trees under 20 inches in dbh with its effects lasting decades. It was not as effective when looking at stand structure and fuel variables over time when comparing fire scenarios that did and did not include management as many of the variables that were significantly different in 2039 were not so 20 to 40 years later indicating a need for recurring management. Mt. Spokane’s simulated dominant fire type over time following the do nothing scenario was conditional crown fire. It indicates two outcomes for stands with this fire type; surface fire behavior, if fire were to enter the stand as a surface fire; or active crown fire, if fire were to enter the stand as a passive or active crown fire. The goal of this work is to provide land managers information on fire hazard and forest conditions through on the ground data, modeling with FVS, and satellite imagery, which can assist with future management decisions.