Modeling a coniferous forest canopy

Abstract

A naturally regenerated Douglas fir stand was modeled by assuming the canopy to be a composite of individual model crowns. The model crown was developed by normalizing total needle surface area per branch position with respect to the maximum foliage surface area and position in the crown. Because of the similarity of foliage distribution between the trees which were examined, it was assumed that all trees in the forest could be represented by this double normalized model crown. The model forest canopy was compiled by scaling model crowns to length of live crown and surface area representative of trees of the respective size classes. The composite forest canopy was obtained by multiplying the number of trees in each size class by its respective surface area (the scaled model crown) and then summing these products. The cumulative plant surface area obtained from the composite canopy was compared with wind profiles obtained within the forest. The results indicate that the plant surface area distributions, as obtained by this method, are valid in that they satisfactorily account for the shape of the wind profiles within the forest. It is suggested that this method of plant surface area determination may be satisfactory for many other types of vegetation.