Forest Floor Consumption and Smoke Characterization in Boreal Forest Fuelbed Types of Alaska

Project Description

The four primary objectives of the boreal forest wildfire study were to:

• Develop a model that predicts forest floor consumption.
• Provide modified combustion efficiency (MCE) for residual smoldering.
• Determine emission factors of major smoldering emission species.
• Determine the rate of carbon release and estimated total fuel consumption for residual smoldering combustion

In completing this project, we surpassed our original objectives by collecting more data than originally proposed, across a fuel moisture range rarely observed in Alaska.

The fuel consumption model and emission factors are implemented into Consume 3.0, which in turn supports a large number of clients, including BlueSky, Fire Effects Tradeoff Model (FETM), Fire Emissions Production Simulator (FEPS), and the Fuel Analysis, Smoke Tracking, and Report Access Computer System (FASTRACS).

This research makes Consume 3.0 and other fuel consumption, fire effects, and smoke production models more robust by account for boreal forest fuelbed types, thereby aiding managers, planners, and researchers in developing environmentally, socially, and legally responsible land management plans. This knowledge enables a more effective and informed use of emission production and wildfire/prescribed fire tradeoff models, which provide improved wildland fire emissions and carbon accounting in the Alaska boreal forest types, and at other local, regional, and global scales.

We acknowledge funding from the Joint Fire Science Program under Project #03-1-3-08.

Purpose and Scope

Land managers can use the predictions of fuel consumed in a fire to help determine when and where to conduct a prescribed burn or to plan for a wildland fire for use to achieve desired objectives while reducing effects on other resources.

Methods

Forest floor consumption was measured at 24 black spruce and white spruce forested sites on U.S. Fish and Wildlife Service, Alaska State Department of Natural Resources, and Bureau of Land Management sites during eight wildfires that occurred in Alaska in 2003 and 2004 (table 1). Figure 2 displays a higher resolution map with the location of plots inventoried and plots burned on the Porcupine, Chicken, Wall Street, and Gardiner wildfires in 2004.

Forest floor reduction was measured as the dependent variable according to procedures adapted from Beaufait et al. (1977; table 2 https://babel.hathitrust.org/cgi/pt?id=umn.31951d02988195r;view=1up;seq=3). Nine to 18 permanent plots were established in an area in front of an active wildfire. Within each plot, 16 forest floor pins were inserted 1.5 feet apart into the forest floor, clipped flush with the lichen, moss, or duff surface around each plot. Because the forest floor is often very deep, lightweight welding rods >60 cm in length were used as forest floor reduction pins.

Several possible independent variables were measured. One forest floor plug about 6 inches square down to mineral soil was collected near each permanent plot. Depths of live moss, dead moss, upper duff, and lower duff layers were measured. Each plug was then separated into live moss, dead moss, upper duff, and lower duff layers, and placed into a labeled and sealed plastic bags. To determine fuel moisture, all samples were oven dried at 70 °C for 96 hours and weighed before and after drying. We also collected shrub and grass moisture content samples. Weather data collected before the burn at each site included temperature, wind speed, and relative humidity.

Following the fire front, each plot was relocated, and the depth of the burn was measured at each forest floor reduction pin. A measurement from the top of the pin to mineral soil provided a total forest floor depth.

Implementation

An equation for fuel consumption in the boreal forest of Alaska was added to improve results from the preexisting software Consume 3.0.

Key Findings

The fuel moisture content of the upper forest floor can be obtained from forest floor samples that are collected, oven dried, and weighed to determine gravimetric fuel moisture content. The preburn forest floor depths require onsite measurements to be collected.

Project Deliverables

• The consumption equation derived during these experiments on the boreal forest floor is:
  Proportion forest floor reduction (%100) = 0.9161 minus (0.0020 × fuel moisture in the lower duff[%]).
• A secondary deliverable is a table of emission factors used to predict emissions from boreal forest wildland fire.
• Consumption algorithm and emission factors developed from this project have been included in the consumption section of Fuel and Fire Tools (FFT).
• The user’s guide, online help, and tutorial that accompany Consume 3.0 have been updated.
• The RX 310 and RX 410 curriculum has been modified to account for the new information.

Additional products and technology transfer have been completed that exceeded the scope of the project.