The Conductance model of plant growth and competition in monoculture and species mixtures: a review

Over the past two decades, an ecophysiological model has been developed for annual horticultural crops and weeds, which has the powerful ability to predict the growth of plants in monoculture and mixed species stands from parameter values derived from plants grown in isolation, even if the species display contrasting canopy architecture. The model can also simulate the effects of different spatial arrangements on plant growth. The purpose of the model is to describe, in simple yet mechanistically-based terms, the effects of contrasting environments and competitive interactions on the growth of individual plants. In the simplest form of the model, growth is described by an empirical growth equation, using time calculated from an integration of the growth-promoting effects of environmental factors. More complex versions of the model include a self-shading component, which provides an algorithm for inter-plant competition based on crown zone areas. This model is termed the 'Conductance model' and this article outlines its development, applications to date, goodness of fit to experimental data, and discusses its strengths and weaknesses and scope for further testing and application. This article, which is dedicated to the late David Aikman, also sets out how the model can be applied to simulating weed-crop competition from simple data sets.