Problem And Approach

Severe wildfires in 2000 testify to the hazardous forest conditions over large areas of New Mexico. The costly consequences of these fires have served to strengthen public support for management actions. However, developing plans to address hazardous conditions at a strategic level requires a fundamental understanding of the problems at hand, and the potential effectiveness and costs of treatments to address them. Consequently, we designed this study to meet the following objectives:

• Profile forest conditions in New Mexico
• Assess fire hazard
• Evaluate effectiveness of hazard reduction treatments
• Estimate treatment costs.

Forest Inventory and Analysis (FIA) data for the state of New Mexico provided us the means to profile forest conditions statewide, and then assess fire hazard. We evaluated fire hazard using the Fire and Fuels Extension (FFE) to the Forest Vegetation Simulator (FVS). Hazard was quantified in terms of Crowning Index, which is the windspeed necessary to sustain a crown fire once a fire has reached the main canopy. Crowning Index values less than 25 miles per hour (mph) were rated high hazard, 25-50 mph as moderate hazard, and greater than 50 mph as low hazard. Fire hazard was evaluated for nine major forest types; however, our analysis primarily focused on short-interval, fireadapted ecosystems. In New Mexico, these are the Ponderosa Pine and Dry Mixed Conifer (PP/DMC) forests where people and property are especially at risk.

We collaborated with representatives from federal, state, and tribal land management entities to develop three treatment prescriptions for reducing fire hazard:

1) Thin-from-Below: remove all trees smaller than 9"
2) Diameter-Limit: reserve all trees >16”; however, if reserve BA <50 ft2/ac, reserve additional trees <16” until BA=50 ft2/ac
3) Comprehensive: ecologically-based; reserve a target basal area of 40-50 ft2/ac, primarily comprised of larger trees.

Fire hazard (i.e., Crowning Index) for each of the three treatments was evaluated immediately after treatment using FFE. Treatment costs and revenues for New Mexico were estimated using a harvest cost model and data bases maintained at the University of Montana. Land management agencies and the private sector provided cost estimates for treating activity fuels.

We used FVS to project post-treatment conditions forward 30 years for each of the treatment alternatives, and then evaluated Crowning Index again using FFE. Projection allowed us to evaluate the durability of hazard reduction treatments through time.

Please open the PDF Document below for the full text

A Strategic Assessment of Fire Hazard in New Mexico