Estimating forest fuels in the Southwest using forest inventory data

Abstract

Catastrophic wildfires occurring over the last several years have led land management agencies to focus on reducing hazardous fuels. These wildland fuel reduction projects will likely be concentrated in shorter interval, fire-adapted ecosystems that have been moderately or significantly altered from their historical range. But where are these situations located? What are their fuel characteristics? Who owns them? Describing fuel characteristics on these lands is not simple, but Forest Inventory and Analysis (FIA) data may be helpful. One objective of this study was to demonstrate the linkages between forest inventory data and hazardous fuel characteristics and to identify information gaps and needed relationships. A second objective was to estimate and contrast overstory and understory biomass, especially in high fire-risk areas. Restricting analysis to Arizona, New Mexico, and Utah, we estimate that understory biomass accounts for 4 to 8 percent (20 to 42 million tons) of total forest biomass. Additionally, we estimate that around 57 percent (619 million tons) of the estimated 1.08 billion tons of biomass is found on high firerisk forest lands. Of these 619 million tons, approximately 434 million tons is associated with larger diameter (> 10 inches) overstory trees, both live and dead, and most is found on nonreserved forestlands (lands where tree utilization is not precluded by statute or administrative designation) administered by the USDA Forest Service. We found that FIA data provides useful data on 92-96 percent of biomass, but we did encounter problems with estimating understory biomass. Some of the problems we encountered included a lack of widely applicable understory biomass equations, no equations for estimating tree seedling biomass using percent cover, and many biomass equations for shrubs that use diameter, a measurement that is not collected by FIA.

Parent Publication

• Proceedings of the 2002 fire conference: managing fire and fuels in the remaining wildlands and open spaces of the Southwestern United States

Citation

Gebert, Krista M.; Schuster, Ervin G.; Woudenberg, Sharon; OBrien, Renee. 2008. Estimating forest fuels in the Southwest using forest inventory data. In: Proceedings of the 2002 Fire Conference: Managing fire and fuels in the remaining wildlands and open spaces of the Southwestern United States; December 2-5, 2002; San Diego, CA. Gen. Tech. Rep. PSW-GTR-189. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 39-48.