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Linda Joyce
Rocky Mountain Research Station
240 West Prospect
Fort Collins, CO 80526
Phone: 970-498-2560
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 M.A. Battaglia, W.D. Shepperd, and M.J. Platten Rocky Mountain Research Station, Fort Collins, CO

Recent large fires in the Colorado Front Range and concern about the volatility of forest conditions in this ecosystem have prompted renewed interest in the need for treating these forests to reduce fuels risk. With this interest comes the need to obtain quantitative data on the fuels that exist under Front Range Forests and to understand how ground fuels vary across differing site and stocking conditions in Front Range landscapes. Here, we present data collected on the 16,700 ac Manitou Experimental Forest west of Colorado Springs, CO. The forest contains a variety of stocking and physiographic conditions in ponderosa pine and mixed conifer forest types typical of the Southern Front Range.

Overstory Sampling – Plots were laid out along a grid of pre-selected GPS coordinates in three distinctly different areas of the Experimental Forest: Trout Creek (n = 313), Hotel Gulch (n = 117), and Rampart Range (n = 49). At each plot, basal area of live and dead trees were tallied by species using 20 BAF. Elevation, slope, and aspect were recorded at Hotel Gulch and Rampart Range.

Fuels Sampling – A nested-plane fuels inventory transect (Brown and others 1982) was oriented on a random bearing from the center of each BAF plot. All fuels intersecting an imaginary vertical plane along each transect were tallied or measured by diameter and soundness class. All pieces in the 0 to ¼ and ¼ to 1 inch diameter classes were tallied in the first 6 ft. of the transect. Fuels from 1 to 3 inches in diameter were tallied up to 10 ft. away from plot center. Diameters of all sound and rotten fuels >3 inches intersecting the transect < 35 ft. from plot center were measured and recorded. Data for each plot was summed to a ton/acre basis by size and soundness class using an Excel spreadsheet program.


Trout Creek Timber Sale: This 2,700 acre area is currently undergoing a restoration harvest to reduce overall stocking and remove live fuels from the understory. This area contains nearly pure ponderosa pine forests on nearly level terrain.

Hotel Gulch: This valley bisects the eastern portion of the Forest from 7,800-9,400 ft elevation. Plots were sampled on both north and south aspects and consisted of a mixture of ponderosa pine, Douglas-fir, limber pine, aspen, and spruce. 

Rampart Range: This high elevation (9,200 – 9,500 ft.) area contained mostly lodgepole pine, Douglas-fir, and limber pine.


Mixed stands had the highest and most variable fuel loadings followed by spruce and aspen (Fig. 1).
No clear relationships between aspect (Fig. 2), elevation (Fig. 3), or plot basal area (Fig. 4) were noted.
15% of all plots contained high (25 to 50 tons per acre) fuel loadings. Most of these plots were found within the Hotel Gulch and Rampart Range areas (Fig. 5).
Average fuel loadings were low in all three areas sampled (Fig. 6).
Trout Creek had lower fuel loadings in all but the ¼ to 1 inch size class (Fig. 6).
The ¼ to 1 inch fuel class contributed the most to total fuel loadings in the Trout Creek area (Fig. 7).
The 3+ inch fuel class contributed the most to total fuel loadings in the Hotel Gulch and Rampart Range areas (Fig. 7).

Figure 1

Pico= Lodgepole pine; Pifl= Limber pine; Pipo= Ponderosa pine; Potr= Aspen; Psme= Douglas-fir; spru= Engelmann and Blue Spruce


Figure 2


Figure 3


Figure 4


Figure 5


Figure 6
Note: Different letters indicate significant difference within fuel size class between locations as calculated by Tukey’s HSD test (p = 0.05).

Figure 7

Although average fuel loadings in the Manitou Experimental Forest are low, there are pockets of high fuel loadings. Fuel loadings in areas dominated by ponderosa pine were much lower than those found in mixed conifer, spruce, and aspen stands. The diverse distribution and types of fuels across this landscape will likely influence fire behavior in different ways.

Brown, James K.; Oberheu, Rick D.; Johnston, Cameron M. 1982. Handbook for inventorying surface fuels and biomass in the interior west. USDA For. Serv. Gen. Tech. Rep. INT-129, 48p. Intermountain forest and Range Experiment station, Ogden, UT 84001.

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