Assessing Spatial Patterns of Plant Communities at Varying Stages of Succession

Abstract

There is a well known connection between the structural complexity of vegetative stands and ecosystem properties. Developing methods to quantify this structural complexity is an important goal for ecologists. We present an efficient and easily implemented field technique for calculating the shape of forest canopies, and the shape of forest stands as succession occurs, using fractal geometry. Fractal geometry can be used to describe complex, non-Euclidean objects that are common in natural systems. We tested the use of this tool in 22 vegetative and forested plots in Western New York State, USA. We found an asymptotic relationship for fractal dimension ( D ) as a function of basal area ( BA ; r 2 = 0.68). In a randomization test to investigate the robustness of D to different tree canopy shapes, we found that D was sensitive to canopy shape switching, suggesting that the method is able to differentiate among similar forests comprised of species having different shaped crowns. We conclude that the shape is conserved in vegetative areas as they progress from one stage of succession to the next (range of mean D : 2.56 to 2.68 across stages). Furthermore, we conclude that the shape filling properties—i.e., distribution of trunks and limbs in a forested area, measured as mean distance—are also conserved across vegetational chronosequences (F = 1.3189, df = 8, 3, p = 0.3341).