Forest regeneration appraisal with large-scale aerial photographs

The operational feasibility of using large-scale aerial photographs to quantify coniferous forest stocking and regeneration density, was assessed over 6 cutovers with a 1,700 ha total area. The project involved two stages: one to pre-stratify cutover stocking levels using 1:10,000 general-coverage, colour photos; and the second to sample intensively, stocking and density using 1:500 large-scale photos. The accuracy, cost and practical problems in using large-scale sampling photos for regeneration assessment were determined. Accuracy assessment included detectability of young trees, species interpretation, and reliability of stocking and density measurements. Stocking estimates were on average, only five percent lower than field survey results but could be calibrated using regression techniques. Large differences between field survey and photo estimates of density in stems/ha suggested such counts should not be made from large-scale photos. Density count differences were attributable to seedlings occurring in dense patches or clumps where field counts were also difficult. If survey objectives and methods are carefully planned, large-scale photos can be a suitable tool for assessing and monitoring the stocking and survival rates of coniferous forest regeneration. Key words: Forest regeneration appraisal, silviculture, inventory, sampling, large-scale photography.