Modeling Plant Competition with the Gaps Object-oriented Dynamic Simulation Model

Modeling inter-species competition is a natural application for dynamic simulation models of agricultural systems. We extended a dynamic simulation model of the soil-plant-atmosphere system, GAPS, to include the case where multiple plant species are growing in competition. The competition model was implemented as an object hierarchy which exchanges information with a crop model hierarchy by means of access procedures. Crop models, atmospheric procedures, and soil-plant water interface procedures required minimal change in order to support the competition model. We implemented two competition models: modified ALMANAC and ‘winner-takes-all’. The modified ALMANAC model requires that crop models of competing plants simulate leaf area index, single-crop light interception, and canopy height. Using this information, the ALMANAC model partitions solar radiation among the competitors. GAPS is written in the object-oriented language Turbo Pascal.