| A unit of Lasting Forests
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A Total Forest Management Plan
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Resource condition and change can be monitored using photography. A good photographic monitoring program can reduce the subjectivity in recording site conditions and provide a permanent record of site conditions for comparison over time. The following photographs from a Master of Science thesis (Streeter 1965) suggests one comparison.
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| Photo sequence indicating vegetational changes from 1924 to 1964 looking across the Gallatin River towards Black Butte, Yellowstone National Park, A, 1924; B, 1949; C, 1961; D, 1964 by R.G. Streeter, 1965 |
A systematic photographic monitoring program will typically be designed with the ability to produce replicable records by easy-to-use methods and permit ready retrieval of those records. (Brewer and Berrier 1984) To accomplish this, referenced and relocatable camera or tevevision positions are necessary from which images can be taken periodically for comparison.
The techniques described here are described more fully by Brewer and Berrier (1984) and Rinehart et al. (1978). Each of the sites (at least 5) described above will be marked on topographic maps, a GPS coordinate determined, and described. The camera point in each site should be chosen so that it provides the most advantageous perspective of the expected change. Permanent landmarks such as boulders or powerline towers will be used to describe a site with respect to the camera point.
The camera points will be marked and referenced with permanent markers. Several types of markers were considered for this purpose. Copper-covered steel survey stakes 18-inches long were chosen in coniunction with numbered aluminum tags nailed to witness trees for reference points. The metal survey stakes are relatively inexpensive (10 for $58.95, Foresters Suppliers, Inc.1985), easy to place, and require little or no maintenance. They can be driven flush with the ground to lessen the chance of vandalism. They are long enough to resist frost heaving and can be located with a metal detector or dip needle. Round, numbered aluminum tags are also available from Forestry Suppilers, Inc. for $6.95/box tags.
GPS location significantly reduces losses and improves time of re-locating points. Not only can images becompared at such points but so also can bird calls and seed collections.
At each camera point one of the metal survey stakes will be driven flush with the ground. Numbered aluminum tags will be nailed to at least 3 trees at the site for triangulating to the camera point stake. Tag numbers with bearings to the camera point, distances, and the dbh and species of witness trees should all be recorded and sketched on a map. To aid in the comparison of photos between years, the same type and speed of film and camera lens should be used each year. Accurate records need to be kept regarding these and other variables such as height of camera lens center from the ground (using a tripod), and the bearing toward which the photo is taken. Copies of previous photos should be taken along in the field to help orient the photographer. Dates and the time of day that photos are taken should be recorded and duplicated as nearly as possible in later photo missions in order to lessen variability in shadows and stages of plant growth.
To determine the rate of soil loss and entrenchment in a road or trail, two of the metal survey stakes would be driven flush with the ground, one on each side of the trail about 3 feet from the trail so that a line drawn between the stakes would be perpendicular to the trail. This site should be carefully chosen at a curve in the trail so the camera point can be located about 15 feet below the perpendicular line with a view up the trail. The camera point should also be located 3-4 feet off the trail to avoid being knocked loose by hikers or washed out. Another metal survey stake will mark the camera point or a short set of measurements given for a temporary center position for a standard white target card of known size or recognizable piece of field equipment. For the photograph, a tent stake will be placed at each of the survey stakes and a tape measure stretched between them. The tape should be at ground level at each of the tent stakes. The card will be placed on its edge direcly below and parallel to the transect line. The photograph is to be taken facing uphill to include the tape measure, the ground beneath it, and the vegatation along the trail. The card in the photograph will enable the scale of the photo to be determined. The area under the tape and the entrenchment of the trail, can be calculated from the photo once the scale is known (Rinehart et al. 1978).
Photographs do not show as much information as can be obtained by a detailed, on-site vegatation study. However, benefits of photographic monitoring include the fact that more than one observer can study the photos at any one time without visiting the site. This provides an alternative to paying experts to gather field data or accepting the subjectivty involved with reports from temporary or inexperience help.
References
Brewer,D L. and D. Berrier, 1984. Photographic techniques for monitoring resource change at backcountry sites. Gen. Tech. Rep. NE-86. Broomall, PA: U.S. Dept. of Agric., U.S.F.S.1 Northeastern For. Exp. Stat. 13 pp.
Curtis, R.O. 1983. Procedures for establishing and maintaining permanent plots for silvicultural and yield research. USDA Forest Serv. Pacific Northwest For and Range Exp. Sta., Gen. Tech Rpt. PNW-155, Portland, OR, 56 pp.
Rinehart, P.R., C.C. Hardy, and H.G. Rosenau. 1978. Measuring trail conditions with stereo photography. J. For. 76:501-503.
Streeter, R.G. 1965. Environmental factors affecting vegetational patterns in the Daly Basin of Northwestern Yellowstone National Park, Montana. Unpub MS Thesis, Virginia Polytechnic Institute, Blacksburg, Va. 83 pp.
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Last revision November 25, 2001.