Estimating populations of whitebark pine in Mount Rainier National Park, Washington, using aerial photography
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Whitebark pine (Pinus albicaulis) abundance is declining in western North America due to white pine blister rust, fire exclusion, and mountain pine beetle. In this study, natural colour aerial photograph (23x23 cm) negatives, scales between (1:2000 and 1:6000) were used to estimate whitebark pine abundance in Mount Rainier National Park, Washington, USA. Ground truth field plots were similar to counts from aerial photographs (80.2% accuracy). Correlation analysis between subpopulation area and abundance was used to supplement incomplete aerial coverage and determine the final whitebark pine abundance in the Park. Whitebark pine density, and vegetation cover type, influenced counts from the aerial photographs. Highly clustered whitebark pine sites demonstrated 7% greater accuracy when compared to sites that exhibited little clustering. Count accuracy was 4-5% more accurate on whitebark pine dominant habitats compared to subalpine fir dominant and subalpine parkland habitat. The total number of living adult whitebark pine within park boundaries was ~22 000, with 3160 adult trees found in the Sunrise region. Aerial photography holds promise as a way to inventory and monitor whitebark pine.