Applying fractal analysis to stem distribution maps

The position and size of trees is basic information available for most forest-research sites. Based on such information, various stand structural indices and measures can be calculated that describe the two-dimensional or three-dimensional forest structure. We used fractal analysis to calculate the box-dimension (D_b) as a measure of structural complexity that can be derived from stem positions and stem diameters. D_b is supposed to combine information on tree size, tree distribution and stem density in a single meaningful measure. We wanted to know how powerful the method is if applied to two-dimensional stem distribution maps. Based on 125 research plots (coniferous, deciduous and mixed stands) we found that across typical forest systems in Germany there is no benefit from using the box-dimension. Stem number and mean tree diameter determined D_b values and there was almost no sensitivity observed for existing differences in stem distribution pattern. We conclude that D_b is a measure of stand density but, for the investigated forests, it does not provide information on tree distribution pattern if applied to the stem base maps.