Ottmar, Roger D.; Vihnanek, Robert E. 2002. Stereo photo series for quantifying natural fuels. Volume IIa: hardwoods with spruce in Alaska. PMS 836. Boise, ID: National Wildfire Coordinating Group, National Interagency Fire Center. 41 p.

A series of single and stereo photographs display a range of natural conditions and fuel loadings in hardwood ecosystems undergoing succession to spruce in Alaska. Each group of photos includes inventory information summarizing vegetation composition, structure and loading, woody material loading and density by size class, forest floor depth and loading, and various site characteristics. The natural fuels photo series is designed to help land managers appraise fuel and vegetation conditions in natural settings.

Keywords: Woody material, biomass, fuel loading, natural fuels, Alaska hardwoods, quaking aspen, Populus tremuloides, paper birch, Betula papyrifera, balsam poplar, Populus balsamifera, white spruce, Picea glauca, black spruce, Picea mariana.

COOPERATORS
This publication was developed by the USDA Forest Service, Pacific Northwest Research Station, Fire and Environmental Research Applications Team with funding provided, in part, by the Joint Fire Science Program.

ACKNOWLEDGMENTS
Special recognition is due Larry Vanderlinden, U.S. Fish and Wildlife Service, Alaska Regional Office; Ed Berg, U.S. Fish and Wildlife Service, Kenai National Wildlife Refuge; Tammy DeFries, Skip Theisen, and Jennifer Allen, Bureau of Land Management, Alaska Fire Service; Ray Kraemer, Alaska Department of Natural Resources, Division of Forestry; and Dale Haggstrom, Alaska Department of Fish and Game. Matt Cerney, Crystal Raymond, Vanessa Kenoyer, Cynthia Tyler, Shelaine Curd, and Diana Olson, USDA Forest Service, Pacific Northwest Research Station, worked on this project in the field and in the office.

AUTHORS
ROGER D. OTTMAR is a research forester and ROBERT E. VIHNANEK is a supervisory forester, USDA Forest Service, Pacific Northwest Research Station, Pacific Wildland Fire Sciences Laboratory, 400 N 34th Street, Suite 201 Seattle, Washington  98103.

PHOTOGRAPH AND INFORMATION ARRANGEMENT
The photographs and accompanying data summaries are presented as single sites organized into two series. Each site contains a wide-angle (50 mm) view photograph, general site, stand, and understory vegetation information, summaries of overstory structure and composition, forest floor depth, loading and constancy, and dead and down woody material loading and density by size class.

Figure 1--Photo series sample area layout. Forty random azimuth line transects (one at each point on the 30- and 150-foot arcs, and two at each point on the 60-, 90-, and 120-foot arcs) and 10-15 clipped vegetation plots (two to three per arc) were located within the sample area. Trees, shrubs and seedlings were inventoried on 12 systematically located sample plots.

SITE INFORMATION
The camera point of each site was located with a global positioning system (GPS) receiver using the WGS-84 datum. Vegetation type (Viereck et al. 1992) and Society of American Foresters (SAF) cover type (Eyre 1980), indicators of current vegetation condition, were assigned for all sites. When available, the fire history of each site was included, based on communications with local land managers. Total unit biomass was computed as a combination of aboveground (understory vegetation, saplings, and trees), forest floor, and woody material biomass.

STAND INFORMATION
Tree species present at each site are listed in order of abundance and the percentages of live stems and dead stems are reported for each species.¹ Crown closure of hardwoods and spruce was measured with a forest densitometer at 95 systematically located points in the sample area. Seedling composition and density were estimated using twelve 0.005-acre circular plots representing 43 percent of the sample area; all trees less than 4.5 feet tall were considered seedlings. Understory spruce coverage (includes spruce with heights to approximately 6 feet) was estimated using line intercept transects (Canfield 1941). Other understory species coverages were estimated using line intercept transects and are listed in order of abundance. The listing of understory species was not meant to be a complete vegetation inventory and may represent only a portion of the actual species richness of the sampled areas.

1See below for a list of scientific and common species names used in this volume.

UNDERSTORY VEGETATION
Lifeforms were divided into tall shrub, low shrub (shrub species that typically do not reach heights greater than 5 feet), herbaceous (forb and graminoid species), and seedling (tree species only) categories. The two most abundant species for each understory vegetation lifeform category are listed, with the cumulative coverage of all applicable species reported for each category. Low shrub and herbaceous vegetation heights were measured at 25 points located systematically throughout the sample area. Low shrub and herbaceous vegetation biomass was determined by sampling 12 square, clipped vegetation plots (2.69 square feet each) also located systematically throughout the sample area (fig. 1). All live and dead low shrub and herbaceous vegetation within each square plot was clipped at ground level, separated and returned to the laboratory for oven drying. Understory vegetation and other collected material were oven-dried at a minimum of 158 °F for at least 48 hours before weighing and determination of area loading. Tall shrubs (Alnus spp. and Salix spp.) and tree seedlings were measured in twelve 0.005-acre circular plots. Coverages were not estimated for these lifeform categories. Tall shrub average height is the average height of shrubs greater than 4.5 feet tall. Tree seedling heights were not measured. Biomass was calculated for tall shrubs from species- and size-specific allometric equations (Roussopoulos and Loomis 1979). Tree seedling biomass was calculated by assuming a typical size (Ottmar and Vihnanek unpublished data) and using the appropriate species- and size-specific allometric equation (Barney et al. 1978, Brown 1976, Roussopoulos and Loomis 1979, Telfer 1969). Equations for Picea mariana were substituted for Picea glauca and .Tsuga mertensiana

SAPLINGS AND TREES
As with tall shrubs and tree seedlings, overstory trees and saplings were sampled in twelve 0.005-acre circular plots located systematically throughout the sample area (fig. 1). Tree measurement data were summarized by d.b.h. size class and by tree status (all, live, or dead). The two most abundant tree species for each size class are listed with their relative density of live and dead stems. Height to crown base (reported as ladder fuel height in previous photo series volumes) was defined as the height of the lowest, continuous live or dead branch material of the tree canopy, and height to live crown was defined as the height of the lowest continuous live branches of the tree canopy. Live crown mass (live branches and foliage) and aboveground mass (crown and bole) values were calculated from species- and size-specific allometric equations (Barney et al. 1978; Brown 1978; Harding and Grigal 1985; Roussopoulos and Loomis 1979; Singh 1981, 1984; Stocks 1980; Yarie and VanCleve 1983).

FOREST FLOOR INFORMATION
Surface material and duff depth were calculated as the average of measurements taken every 5 feet between the 30- and 150-foot arcs of the three center transects for a total of 75 measurements (fig. 1). Duff depths were measured from the bottom of the surface material layer to the top of the mineral soil layer (or to ice). The depth of the different forest floor types was calculated as an average of the depth only where that type was encountered during sampling. Therefore, the depths reported for the different forest floor types are not unit-wide averages, and do not necessarily sum to total depth. Loading of each surface material and duff type was calculated from bulk density values derived from field measurements (table 1), and was weighted by depth and constancy. Constancy is an indicator of how consistently the various forest floor components occur in the sample area, and is expressed as a percentage of the total number of measurements. The amount of exposed mineral soil at each site can be estimated by subtracting the constancy of the total forest floor from 100 percent.

WOODY MATERIAL
Measurement techniques used for inventorying dead and down woody material were patterned after the planar intersect method outlined by Brown (1974) and described by Maxwell and Ward (1980). Forty transects of random azimuth starting at 25 systematically located points within the sample area were used to determine woody material loading and density (fig. 1). Woody material data are reported by size classes that correspond to timelag fuel classes used in fire behavior modeling (see, for example, Burgan and Rothermel 1984).² Woody material in 10-hour, and 100-hour and larger size classes was tallied on transects that were 10 feet and 30 feet long, respectively. Woody material loading in the 1-hour size class (and the 10-hour and 100-hour size classes for several of the sites) was determined by collecting, oven drying, and weighing all pieces in twelve 2.69-square-foot sample plots. The decay class and the actual diameter at the point of intersection were measured for all pieces >3 inches in diameter. All woody material <=3 inches in diameter was considered sound. Woody material loading and woody material density were calculated from relationships that use number of pieces intersected and transect length (and wood specific gravity for loading) developed by Brown (1974) and Safranyik and Linton (1987), respectively.

21-hour, 10-hour and 100-hour fuels are defined as woody material <=0.25 inch, 0.26-1.0 inch and 1.1-3.0 inches, respectively.

SPECIES LIST
Scientific and common species names are from Hitchcock and Cronquist (1973), unless otherwise noted.

LITERATURE CITED

Barney, R.J.; VanCleve, K.; Schlentner, R. 1978. Biomass distribution and crown characteristics in two Alaskan Picea mariana ecosystems. Canadian Journal of Forest Research. 8: 36-41.

Brown, J.K. 1974. Handbook for inventorying downed woody material. Gen. Tech. Rep. INT-16. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 24 p.

Brown, J.K. 1976. Estimating shrub biomass from basal stem diameters. Canadian Journal of Forest Research. 6: 153-158.

Brown, J.K. 1978. Weight and density of crowns of Rocky Mountain conifers. Res. Pap. INT-197. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 56 p.

Burgan, R.E.; Rothermel, R.C. 1984. BEHAVE: fire behavior prediction and fuel modeling system--FUEL subsystem. Gen. Tech. Rep. INT-167. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 126 p.

Canfield, R.H. 1941. Application of the line interception method in sampling range vegetation. Journal of Forestry. 39: 388-394.

Eyre, F.H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [+ map]. Forestry Canada Fire Danger Group. 1992. Development and structure of the Canadian Forest Fire Behavior Prediction System. Inf. Rep. ST-X-3. Ottawa, ON: Environment Canada, Canadian Forestry Service, Headquarters. 64 p.

Harding, R.B.; Grigal, D.F. 1985. Individual tree biomass equations for plantation-grown white spruce in northern Minnesota. Canadian Journal of Forest Research 15: 738-739.

Little, E.L.; Pauley, S.S. 1958. A natural hybrid between black and white spruce in Minnesota. American Midland Naturalist. 60(1): 202-211.

Maxwell, W.G.; Ward, F.R. 1980. Guidelines for developing or supplementing natural photo series. Res. Note PNW-358. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 16 p.

Roussopoulos, P.J.; Loomis, R.M. 1979. Weights and dimensional properties of shrubs and small trees of the Great Lakes conifer forest. Res. Pap. NC-178. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station. 6 p.

Safranyik, L.; Linton, D.A. 1987. Line intersect sampling for the density and bark area of logging residue susceptible to the spruce beetle, Dendroctonus rufipennis (Kirby). Inf. Rep. BC-X-295. Victoria, BC: Canadian Forestry Service, Pacific Forestry Centre. 10 p.

Singh, T. 1981. Biomass equations for ten major tree species of the prairie provinces. Inf. Rep. NOR-X-242. Edmonton, AB: Environment Canada, Canadian Forestry Service, Northern Forestry Research Centre. 35 p.

Singh, T. 1984. Biomass equations for six major tree species of the Northwest Territories. Inf. Rep. NOR-X-257. Edmonton, AB: Environment Canada, Canadian Forestry Service, Northern Forestry Research Centre. 22 p.

Stocks, B.J. 1980. Black spruce crown weights in northern Ontario. Canadian Journal of Forest Research. 10: 498-501.

Telfer, E.S. 1969. Weight-diameter relationships for 22 woody plant species. Canadian Journal of Botany. 47: 1851-1855.

Viereck, L.A.; Dyrness, C.T.; Batten, A.R.; Wenzlick, K.J. 1992. The Alaska vegetation classification. Gen. Tech. Rep. PNW-GTR-286. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 278 p.

Viereck, L.A.; Little, E.L. 1972. Alaska trees and shrubs. Agriculture Handbook No. 410. Washington, DC: U.S. Department of Agriculture, Forest Service. 265 p.

Yarie, J.; VanCleve, K. 1983. Biomass and productivity of white spruce stands in interior Alaska. Canadian Journal of Forest Research. 13: 767-772.