Voronoi diagrams to model forest dynamics in French Guiana

Voronoi tessellation is an exhaustive partitioning of space in a finite set of non-overlapping continuous regions called Voronoi polygons. Such construction is defined from a finite set of distinct points. To each point (also called generator point) is associated the region of the plane which is nearer to this particular generator point than to any other (Okabe et al. 1992). In plant ecology, plant coordinates are used for generator points. Plants, being sedentary, experience the environment only in their immediate neighbourhood. Brown (1965) and Mead (1966) were the first ecologists to represent the space that closely surrounds a plant by Voronoi polygons. Brown uses Voronoi polygons as “area potentially available” to a plant, i.e. the available area for a plant to satisfy its needs in water, nutrients and light. A generator point can also be compared to a tree trunk and the associated polygon to the ‘crown projection area’ of the corresponding tree, used by foresters (Bouchon 1979). Voronoi tessellation (Fig.1) gives a detailed description of the position, size and shape of individual plants in relation to the number and proximity of their contiguous neighbours. Hence, polygon features reflect local variations in plant density.