Category: Ecological Research
Title: Changes in Ponderosa Pine Forests of the Mt. Logan Wilderness.
Author: * Waltz, A.E.M. , * Fule, P.Z.
Subject: Ponderosa pine (Pinus ponderosa), Mt. Logan, Fire scars, Pre-settlement
Abstract: Ponderosa pine forests in the Mt. Logan Wilderness on the Arizona Strip have become dense with young trees and highly susceptible to catastrophic wildfire due to exclusion of the natural frequent-fire regime and the effects of livestock grazing and logging associated with Euro-American land use practices. As part of a broader regional ecological restoration study, the Mt. Logan Wilderness was sampled for fire scarred trees, vegetation, and fuels between 1995 and 1997. Reconstructed fire histories show that fires recurred about every 5-6 years prior to settlement, with larger fires burning every 9-12 years. Frequent fires ceased after 1869-1879 in the Mt. Logan Wilderness, coincident with the time of Euro-American settlement, beginning a fire-free period that has lasted up to the present except for a few fires in the 1930s. Current forests are dense, ranging from approximately 700 to 3,000 trees/ha, and dominated by small trees. At both unthinned and thinned sites on basalt soils within the wilderness, tree canopy cover is over 50(percent) and tree basal area is high, 39-40 m2/ha. Understory cover and species diversity are generally low, but slightly higher on cinder soils where shrubs form an important understory community and where tree density is somewhat reduced. Living and dead fuels, including plants, woody debris, and the forest floor , will easily support high-intensity wildfires. In contrast, the presettlement forest was relatively open, with tree densities ranging from approximately 80-100 trees/ha and basal areas ranging from 10-15 m2/ha, dominated by large ponderosa pine trees. In ecological terms, prospects are good for restoring the Mt. Logan Wilderness to emulate the ecological structure and fire disturbance regime of the presettlement reference condition. The current forest is similar to nearby ecosystems where thinning, burning, and fuel treatments are being implemented. However, ecological information is only one component contributing to the debate over appropriate management values and practices in wilderness areas on public lands.
Source: ERI Research Progress Report
Publisher: NAU Ecological Restoration Institute, http://www.eri.nau.edu