COMPARISON OF METHODS FOR ESTIMATING FOREST OVERSTORY COVER - DIFFERENCES AMONG TECHNIQUES

Thirteen techniques for estimating forest overstory cover or mean crown completeness were tested for differences in angle of view of the technique and interaction with mean crown completeness or height to base of live crown. With increasing angle of view from common locations, mean estimates of mean crown completeness increased and the standard deviation decreased. For techniques with angles of view >30° there was interaction among techniques with changing overstory cover. As mean crown completeness increased, the differences between wide- and narrow-angled techniques decreased and converged to 0 at a rate dependent on angle of view. The estimate of mean crown completeness generally increased with height to base of live crown. The more narrow the angle of view the greater was the effect of increasing height to base of live crown. -from Authors