Past Fires Shed Light on Future

Wildfires are often viewed as hazards to people, property, and wildlife. However, scientists at the Fort Collins Science Center (FORT), Biological Resources Discipline, U.S. Geological Survey and their colleagues from the University of Arizona's Laboratory of Tree-Ring Research are gaining new insights on the role of fire in maintaining healthy forest ecosystems.

During the past eight years, scientists have sampled and dated over 3,300 fire scars from about 400 trees, snags, logs, and stumps in the Jemez and Sangre de Cristo Mountains of northern New Mexico to help define the natural range of variability among fires. Specifically, scientists are investigating historical fire frequencies, extent, seasonalities (when fires are most likely to burn), and intensities, and comparing them to current fire regimes.

Findings thus far indicate that high-frequency, low-intensity surface fires were once widespread in the Jemez Mountains and helped maintain open forests with grassy understories. Since the late 1800's, livestock grazing and fire suppression have inhibited natural fire regimes, causing changes in plant species composition, increased tree densities, and a buildup of ground fuels in most forests. "These changes threaten the health of forests in the Jemez Mountains," states Craig Allen, a research ecologist at FORT, "by increasing the chances of unnaturally severe insect outbreaks and large, uncontrollable crown fires." Allen further notes that the information gained from studying fire histories provides scientists and resource managers with a better understanding of the natural role of fire in sustaining and renewing ecosystems.

Research findings strongly support the use of prescribed fires as a management tool for maintaining healthy forest habitats. Frequent, low-intensity fires control vegetation patterns, prevent the buildup of heavy ground fuels, recycle nutrients, and may play a role in controlling some forest diseases.

Related BRD research examines the effects of modern fires on ecosystem components and processes, including vegetation succession, erosion, the nitrogen cycle, breeding birds (including Mexican spotted owls), elk, and arthropods. This research involves collaborative efforts between the National Park Service, U.S. Forest Service, University of New Mexico, Los Alamos National Laboratory, University of Arizona's Laboratory of Tree-Ring Research, and the U.S. Geological Survey. Some of this fire ecology research will be presented in the upcoming publication:

"Fire Effects in Southwestern Forests: Proceedings of the Second Symposium on the La Mesa Fire". C.D. Allen (tech. ed.). 1996. USDA Forest Service, Rocky Mtn. Forest and Range Experiment Station, General Technical Report, Fort Collins, Colorado.