Influence of canopy structure assumptions on predictions from Beer's law. A comparison of deterministic and stochastic simulations

Since Monsi and Saeki introduced the use of Beer's law to describe light extinction in plant canopies, this law has experienced wide use. Many authors have proposed models for describing foliage distribution within the canopy, with many different crown distribution assumptions. This paper explores seven canopy models and the consequences of these canopy models on prediction of light extinction. These seven canopy models range from three-dimensional homogeneity of the entire canopy space to a three-dimensional crowns predicted for each tree. Light extinction predictions using both deterministic and stochastic methods allow examination of different sources of variation within the canopy. Average light extinction at the base of the canopy was found to be equivalent for all models and assumptions, The models varied markedly, however, in the pattern of the average light extinction within the canopy, as well as in the variation expressed at specific points within the canopy. Discussion of the implications of these simulations, given the various assumptions and objectives, provide some suggestion as to the appropriate use of Beer's law.