Abstract
Two fractal dimensions of tree crown images, Ds for silhouettes and Do for outlines, were examined in relation to crown transparency (CT) using 137 standard photographs for the visual assessments of CT in the European forest health monitoring program. The automatic thresholding and the dilation method were applied using NIH Image to estimate Ds and Do. It was found that Ds and Do can not necessarily specify a level of CT, and rather, they were associated with the two components of CT, the foliated area and foliage transparency. A new measure DSO (=Ds-Do) is proposed and tends to decrease curvilinearly with increasing CT, with DSO being close to 0 at CT=100%.
