Modeling plant competition with the GAPS object-oriented dynamic simulation model

Modeling interspecies competition is a natural application for dynamic simu lation models of agricultural systems. We extended a dynamic simulation mod el of the soil-plant-atmosphere system, GAPS, to include the case where mul tiple plant species are growing in competition. The competition model was i mplemented as an object hierarchy that exchanges information with a crop mo del hierarchy by means of access procedures. Crop models, atmospheric proce dures, and soil-plant water interface procedures required minimal change in order to support the competition model. We implemented two competition mod els: modified ALMANAC and winner-takes-all. The modified ALMANAC model requ ires that crop models of competing plants simulate leaf area index, single- crop light interception, and canopy height. Using this information, the ALM ANAC model partitions solar radiation among the competitors. GAPS is writte n in the object-oriented language Turbo Pascal.