COTCO2 - A COTTON GROWTH SIMULATION-MODEL FOR GLOBAL CHANGE

In conjunction with the Free-Air-CO2-Enrichment (FACE) project, a new, physiologically based, mechanistic, modular simulation model of cotto n (Gossypium hirsutum L.) physiology, growth, development, yield and w ater use has been constructed. It is named COTCO2 for cotton response to atmospheric CO2 concentration. The model is capable of predicting c otton crop responses to elevated atmospheric CO2 concentrations and po tential concomitant changing climate variables. The major plant proces ses known to be influenced by CO2 are simulated explicitly, i.e. photo synthesis, photorespiration, and stomatal conductance, and its role in leaf energy balance. The model explicitly simulates the impact of atm ospheric CO2 concentration on C3 photosynthesis and photorespiration a t the level of carboxylation and oxygenation. Growth is simulated for individual organs, i.e. leaf blade, stem segment, taproot and lateral roots, and fruit which includes squares and bolls. Potential growth is calculated and the carbohydrate and nitrogen required to meet this po tential are calculated. Actual growth is based on substrate availabili ty, the potential growth, and water stress. Our intent here is to desc ribe the overall structure of the model, its present status, and futur e development plans. Further development, documentation, calibration, and validation of the model is in progress. The long range goal of the project is to provide quantitative estimates of global cotton product ion in a future higher-CO2 world.