A new model to simulate forest growth

Tree development within a forest largely depends on how much space they have both on the ground and in the air, around the treetops. Trees compete to dominate the space they need to develop, and this relates these biological systems directly to Voronoi diagrams. A Voronoi diagram can be seen as the space partition as a result of expanding the sites in the diagram.

Vorest users can examine what impact the space the trees take up has on the development of a forest. This includes the space transfer dynamics between neighbouring trees dictated by their life strategies, and the outcome in terms of tree growth and mortality. Vorest’s simulation process is based on the fact that any tree is surrounded by an influence region of variable size that determines the future growth of the individual tree.

User flexibility

Vorest automatically calculates the influence regions, but offers users a wide range of options for deciding how growth should be simulated depending on this region. The application outputs two key classes of visual information.

First, Vorest represents the Voronoi diagram modelling the influence regions of each of the trees loaded in the program at any point of their growth. Second, it generates a more or less detailed representation of what the trees could really be expected to look like in their natural environment. The application then is able to generate a detailed 3D scene of what the forest really looks like.

Users will be able to manipulate this scene using textures to improve soil appearance or even by configuring the SkyBox representation. This produces a basic, but effective 3D background effect. The application has a straightforward and easy-to-use interface, and users have no need of computing expertise to operate the system.

The model was developed by Manuel Abellanas and Carlos Vilas from the Department of Applied Mathematics at the Universidad Politécnica de Madrid’s School of Computing and by Begoña Abellanas from the Department of Forestry Engineering at the Universidad de Córdoba. They were advised by Professor Oscar García from Canada’s Northern British Columbia University, who was a visiting professor at the Department of Applied Mathematics this year.

Useful models

Forest simulation models or forest growth models are very useful for forest managers and forestry researchers in many respects. A forest growth model aims to describe the dynamics of the forest closely and precisely enough to meet the needs of the forester or forestry researcher.

Dynamics includes all the change processes throughout the forest’s or tree’s lifetime. The primary changes in the forestry field are related to the incorporation, growth and death of trees, a forest’s key asset. There are many forest growth models. Vorest models the individual tree.

The most common uses of these models for managers are to forecast timber production or, less often, other forestry products (cones, cork, etc.) and to simulate different forestry management alternatives with a view to decision making. The models help to forecast what long-term effects a forestry management intervention is likely to have on both timber production and the future conditions of the actual forest, as well as the impact of interventions on other forest values.

For forestry researchers, models are most useful as tools for researching forest dynamics. A forest growth model like Vorest describes the dynamics of the forest closely and precisely enough to meet the needs of forestry managers or forestry researchers.