Application of large- and medium-scale aerial photographs to forest vegetation management: A case study

Five experimental conifer release treatments applied to each of four, three- to seven-year-old spruce plantations resulted in a mosaic of woody and herbaceous vegetation complexes after two growing seasons. A combination of 1:5000-scale overview and 1:500-scale sample photographs were evaluated as a means of mapping and quantifying cover in each of eight vegetation and two non-vegetation categories. On 23-cm format, 1:5000-scale photographs, blocks were stereoscopically stratified into areas (> 25 m(2)) of uniform vegetation. A random selection of eighty 70-mm format, 1:500 photo samples were then used as "training sites" to calibrate strata assessment on the 1:5000 photographs. Remaining sample plots were used to verify the accuracy of the: final map product. Verification plots suggested that principle vegetation components such as tall, mid, and low shrub, grass, and herbaceous species were estimated to within 5-10% cover, at least 70% of the time. Errors for lesser components, such as dead shrub, conifer, bare ground and slash were 2-5% cover. Ferns could not be discerned at the 1:5000 scale and there was evidence of occasional confusion between herbaceous species and other life forms, including mid shrub, low shrub, and grass categories. Operational applications of the methodology are discussed.