Developing FCCS Fuelbeds for the Lake Tahoe Basin

Project Description

FERA collaborated with the Pacific Southwest Region to develop a set of past, current, and future fuelbeds for the Lake Tahoe basin using the Fuel Characteristic Classification System (FCCS). The system provides fuel characteristics; carbon accounting; surface fire, crown fire and available fuel potentials; and fire behavior calculations under various weather scenarios for each fuelbed developed. Following assignment of the fuelbeds to the basin landscape, levels of fire risk, smoke/pollutant production, carbon gain or loss, and threats or benefits to other resources were compared among the various treatment alternatives considered by the Interdisciplinary Team and Lake Tahoe Basin Management Unit Vegetation and Fuels Managment staff. This was done to improve the planning of restoration projects and serve as a common platform of communication among managers, decisionmakers, and the public.

Purpose and Scope

As fire models become more sophisticated and widely used, there is an increasing need to accurately quantify and classify the structural and geographical diversity of wildland fuels. Defining these fuelbeds provided information for current and future fire and fuel models, enabling managers to better plan restoration projects, quantify potential fire behavior, fire effects, and smoke emissions, account for carbon, and protect and enhance wildlife habitat throughout the Lake Tahoe Basin Management Unit (LTBMU).

Although the LTBMU has fire behavior fuel model maps, those do not provide a representation of realistic fuels required by today’s planning processes. Consequently, the LTBMU collaborated with the Fire and Environmental Research and Applications (FERA) team of the Pacific Wildland Fire Research Laboratory to create a comprehensive set of Fuel Characteristic Classification System (FCCS) fuelbeds representing the past, current and potential future conditions of major forest and rangeland types, management activities, and natural disturbances occurring within the LTBMU.

Methods

A team of LTBMU fire ecologists and fire and fuel experts were gathered to list a set of important fuelbed types for the unit. A fuelbed pathway (similar to a successional forest pathway but for fuelbeds as they change over time) was created for each fuelbed type. The pathways identified fuelbeds to construct representing major forest types, natural succession, common management activities and natural disturbances over time. In addition, 20 fuelbeds were added to the fuelbed list that did not fall within the key fuel types identified by the LTBMU managers, but allow a more complete assignment of fuelbeds to vegetation classes found in the LTBMU.

FCCS version 2.1 was used to calculate (1) FCCS surface fire behavior, crown fire, and available fuels potentials; and (2) reaction intensity, rate of spread, and flame length for each fuelbed at three moisture scenarios (low, medium, and high), mid-flame windspeeds (0, 3, 7 mph) and slopes (0, 30, 70%).

General information on the fuelbed types, fuelbed pathways, fuelbeds, fire potentials, surface fire behavior prediction, and fire behavior fuel model crosswalk were compiled into a Lake Tahoe Basin Fuelbed Pathway Handbook. The fuelbed types and pathways information is summarized in schematics and tables that include the fuelbed names, description, the age class, and any management actions or natural change agents associated with each fuelbed.

Photos were collected and added to the handbook to illustrate general structural features of the fuelbeds only and were not intended to represent actual species composition or fuel loadings.

To map FCCS fuelbeds we used CALVEG data for the Lake Tahoe Basin Management Unit. The vegetation type (Regional Dominance type) and overstory tree size class were used to create unique classes. These unique vegetation classes matched closely with the fuelbed type, age, and characteristics of the pathways and fuelbeds and a simple crosswalk was created. Once a fuelbed map produced, it was discovered that there were more vegetation classes than fuelbed types developed for the basin and the map coverage was less than 90 percent. To improve map coverage, 20 additional fuelbeds outside the fuelbed types were constructed and added to the map to achieve a +99.5 percent fuelbed coverage of the Lake Tahoe Basin Management Unit.

Key Findings

There were 6 fuelbed types identified by the LTBMU managers and six fuelbed pathways developed to account for natural succession, fuels management activities, and natural and human change agents. Harvest types, fuel treatments, and natural change agents were considered when constructing the pathways and included: clearcut, pre-commercial thin, select-cut, salvage, pile and burn, pile and no burn, prescribed fire, mastication; crown wildfire, ground wildfire, insect and disease, avalanche, and none. The fuelbed types and number of fuelbeds constructed for each type include:

• Jeffrey and white fir (28 fuelbeds)
• Red fir (22 fuelbeds)
• Wet lodgepole pine (eight fuelbeds)
• Whitebark pine, lodgepole pine (eight fuelbeds)
• Moutain hemlock (six fuelbeds) Mixed conifer (28 fuelbeds)

Twenty additional fuelbeds were identified and constructed to account for vegetation not covered by the six fuelbed types but that represented a significant portion of the LTBMU landscape.

The total loading ranged from 1.4 tons per acre for the low sagebrush additional fuelbed LF308 with only shrub biomass to mixed conifer LT064 fuelbed 80-120 years old with a substantial tree bole and woody fuel mass. The shrub, grass, woody fuel, and litter fuelbed categories drive the surface fire behavior reaction intensity, spread rate and flamelength for surface fire behavior. Total biomass for these four categories ranged from 1.1 tons per acre for the additional bitterbrush fuelbed CO208 with no litter and small woody fuels to 17.7 tons per acre for the mixed conifer fuelbed LT088 120+ years.

FCCS surface fire behavior, crown fire, and available fuels potentials; reaction intensity, rate of spread, and flame length; suggested crosswalks to the original and standard fuel models are presented in summary tables of the Lake Tahoe Fuelbed Pathway Handbook