ISHS Acta Horticulturae 276: II International Symposium on Computer Modelling in Fruit Research and Orchard Management
A SIMPLIFIED DRY MATTER PRODUCTION MODEL FOR APPLE USING AUTOMATIC PROGRAMMING SIMULATION SOFTWARE |
| Authors: | A.N. Lakso, R.S. Johnson |
| Abstract:
Previous research on modelling of dry matter production and yield of apple trees has resulted in complex models that have remained incomplete or inadequately described and tested. The complexity of both the physiological processes and the programming needed to describe them often limits the usefulness of these models primarily to their originators. To overcome some of these limitations, a simplified dry matter production model has been developed with the user-friendly "Stella" dynamic simulation automatic programming language on a Macintosh. This language can be used effectively by researchers not trained in programming, thus greatly expanding the potential use and testing of the model by other researchers. Compared to earlier models the model described here is simplified in several ways. The most important is that the basic time step is one day rather than one minute or hour. Using the daily integral eliminates the complexity of the diurnal changes in radiation geometry. The daily photosynthesis (P) integral is calculated as described by Charles-Edwards from maximum P rate, photochemical efficiency, daily integral of light, daylength, canopy extinction coefficient and leaf area index (or fraction of available light intercepted). Leaf area development is based on degree-day accumulation, a constant leaf area production/degree-day, the total shoot numbers and the fraction of shoots growing at any time. Respiration is driven by temperature. Wood and leaf respiration are based on surface areas; fruit respiration on weight. Estimates of dry matter/carbon ratio are varied over the season depending on estimates of costs of synthesis of dry matter components. Evaluation of the assumptions and limitations is continuing, although initial testing with data from the literature has been promising. Validation testing by growth analysis in field trees has begun. | |
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