COTCO 2 : a cotton growth simulation model for global change 1 Gerard

In conjunction with the Free-Air-CO2-Enrichment (FACE) project, a new, physiologically based, mechanistic, modular simulation model of cotton (Gossypium hirsutum L.) physiology, growth, development, yield and water use has been constructed. It is named COTCO2 for cotton response to atmospheric CO 2 concentration. The model is capable of predicting cotton crop responses to elevated atmospheric CO2 concentrations and potential concomitant changing climate variables. The major plant processes known to be influenced by CO2 are simulated explicitly, i.e. photosynthesis, photorespiration, and stomatal conductance, and its role in leaf energy balance. The model explicitly simulates the impact of atmospheric CO2 concentration on C3 photosynthesis and photorespiration at 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 potential are calculated. Actual growth is based on substrate availability, the potential growth, and water stress. Our intent here is to describe the overall structure of the model, its present status, and future 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 production in a future higher-CO2 world. 1 Contribution from the Agricultural Research Service, US Department of Agriculture. Supported in part by the US Department of Energy, Carbon Dioxide Research Division, Office of Health and Environmental Research, Atmospheric and Climate Research Division under Interagency Agreement No. DE-AI05-88ER69014. * Corresponding author 0168-1923/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0168-1923(94)05041-4 290 G.W. Wall et al. / Agricultural and Forest Meteorology' 70 (1994) 289-342