Application of L-systems to geometrical construction of chamise and juniper shrubs

Improved models of fire spread and fire characteristics are desired for live shrub fuels, since the majority of existing research efforts focus on either dead fuel beds or crown fires in trees. Efforts have been made to improve live fuel modeling, including detailed studies of individual leaf combustion, with results incorporated into a shrub combustion model for broadleaf species. However, this approach was not well-suited to non-broadleaf shrubs since their fuel consists of long needle-covered branches rather than easily discretized leaves. Methods were therefore developed to simulate the branching structure of chamise (Adenostoma fasciculatum) and Utah juniper (Juniperus osteosperma). The plant structure was based on a form of fractal theory called Lindenmayer systems (i.e., L-systems). Correlations to predict branch number from crown diameter were made based on data from the literature, to ensure that the modeled shrubs would have the same bulk density as live shrubs. The structure model was designed to match the specific characteristics of each species, such as branching angles, the number of stems exiting at ground level, and the fuel element length. This method can be used to generate shrub geometries for detailed shrub combustion models or for realistic artistic renditions.