It is generally assumed that insect and disease epidemics, such as those caused by the mountain pine beetle, predispose damaged forests to high fire danger by creating highly flammable fuel conditions.

While this may certainly be true in some forests, these dangerous fuel conditions many only occur for a short time when evaluated at a landscape level. Others feel these epidemics may cause high surface fuel loadings when the dead material from dead trees falls to the ground. These high fuel loadings may result in abnormally severe fires. This study will evaluate, through intensive field collections and simulation modeling, the effect that exogenous disturbance events, namely fire and beetles, have on future fire hazard and risk. We will measure surface fuel deposition and decomposition rates for a number of forest types after wildfire events and after beetle epidemics to quantitatively describe fuel dynamics to ultimately estimate resultant fire behavior in heavy mortality stands for up to 10 years after the disturbance. Fuel deposition will be measured using semi-annual collections of fallen biomass sorted into six fuel components (fallen foliage, twigs, branches, large branches, logs, and all other material). This litterfall will be collected using a network of seven, one meter square litter traps installed on plots established on seven sites across the northern Rocky Mountains USA. We will also measure decomposition using litter bags installed in one sets of five bags for three surface woody fuel components and monitor biomass loss from the bags each year for 5-10 years. We will also measure stand and fuel characteristics of the plot using FIREMON techniques at the beginning, and every year till the end of the study. We will last quantify fire behavior for each plot using collected or measured tree and fuels data, local weather summaries coupled to the BehavePlus fire model and the NEXUS crown fire model. We will summarize and report fuel deposition and decomposition rates in these disturbed stands over the 10 year period and the describe fire hazard in these stands for each of the 10 years.

PRICIPAL INVESTIGATOR

Robert E. Keane, Deputy Program Manager, Fire, Fuel, and Smoke Science (FFS); Research Ecologist; Director, Fire Modeling Institute (FMI)

Staff

Jhen Rawling, Violet Holley, Signe Leirfallom, Laurie Dickinson, Curtis Johnson

GOALS AND OBJECTIVES

The project has one primary objective and a number of specific objectives:

• Determine if recently disturbed stands in the northern Rocky Mountains have high fire hazard

This objective will be achieved using the following steps described as sub-objectives;

• Measure the litterfall and decomposition rates of major fuel components across major forest types in the northern Rocky Mountains after a major disturbance event for 10 years
• Measure stand conditions at the beginning, and every year to year 10 of this study
• Implement findings in ecosystem models containing explicit simulations of fuels dynamics
• Model fire behavior and fuel conditions in these stands for the decade after the disturbance events using the collected stand data
• Model fire behavior and fuel conditions after the 10 years of this study using ecosystem models parameterized using the data from this study

The audience for this effort is managers and researchers interested in describing and sampling fuels after stand-replacement disturbances for future fire behavior and effects prediction. This research may lead to new methods of prioritizing fuel treatments after major insect, disease, or fire events and it will provide important parameters and values for fuel sampling efforts.

METHODS AND RESULTS

We have established one plot on a number of sites that represent major forest types across Montana and Idaho (Table 1). Three plots in the Red River lodgepole pine stands were established immediately after a mountain pine beetle epidemic in 2002 near Elk City ID and were originally part of the FUELDYN study (Keane 2008). The remaining sites were established in the summer of 2007. These sites were selected using strict topographic criteria: flat, near road, hidden from view.

Table 1. List of sites that are included in this study

At each plot, we will measure a number of topographic, vegetation, and ecosystem characteristics on 0.1 acre (0.04 ha) circular plots using the FIREMON sampling methodology (Lutes and others 2006). All plot measurements will be done in the autumn for every site and at the time of installation of the litter traps. We will fill out a FIREMON PD, TD, FL, and SC form, along with a separate log inventory form, each year for each plot. The plot measurements will be taken in the early summer if possible.

At each plot, we have installed 7 litter traps to collect fallen biomass. The litter traps were constructed by creating a 1x1 meter frame (inside dimensions) with 2x9 cm (1x6 inch) boards and then tacking a coarse grid hardware cloth on the bottom of the frame to allow water drainage and minimize losses from accumulated material due to decomposition and wind (Figure 5). We also tacked a plastic screen (mesh size 0.7 mm) on top of the hardware cloth to block fine material from falling through the coarse hardware grid and to facilitate litter collection. All collected material is sorted to size class and fuel type and placed in paper bags that are later dried at 85 degC for two days then weighed. We will use litter bags to estimate the rate of decay for the four fuel components of freshly fallen foliage, twigs, branches, and large branches. We will make these bags by sewing a fiberglass screen with a pore size of about 2 mm for the top with a rumen bag or pool cover material with a pore size of 0.055 mm for the bottom. We will put approximately 100-150 g of material taken from the small sample of fuels collected from the litter traps (see previous section) into each bag. At each plot, we will install one set of five bags for the three fine woody fuel components (1, 10, and 100 hour timelag). One set was placed near plot center, with another at about 7 meters (23 feet) northwest of plot center, and the third about 7 meters southeast of plot center. Decomposition is measured over three years by taking one bag from each wire set every 12 months. The litter bags will be placed in paper bags and brought back to the laboratory to be dried at 80oC for three days and weighted to the nearest 0.01 g with the weight, tag number and tag date recorded for analysis.

REFERENCES

Keane, R.E. 2008. Biophysical controls on surface fuel litterfall and decomposition in the northern Rocky Mountains, USA. Canadian Journal Forest Research 38:1431-1445

Keane, Robert E. 2008. Surface fuel litterfall and decomposition in the northern Rocky Mountains, USA. USDA Forest Service Rocky Mountain Research Station Research Paper RMRS-RP-70. 22 pages

Lutes, D. C., R. E. Keane, J. F. Caratti, C. H. Key, N. C. Benson, S. Sutherland, and L. J. Gangi. 2006[in press]. FIREMON: Fire effects monitoring and inventory system. General Technical Report RMRS-GTR-164-CD, USDA Forest Service Rocky Mountain Research Station, Fort Collins, CO USA

FUNDING ORGANIZATIONS

This work is currently being funded by RMRS and Missoula Fire Fuels and Smoke Program.

PROJECT STATUS

This is a 10 year study where litter and decomposition will be measured from 2001 (Red River) and 2007 to 2017.

ADDITIONAL INFORMATION

FUELDIST study plan