Improving the Suitability of the DSSAT Canegro Model for Simulating Sugarcane Responses to Climate Change.

AgMIP sugarcane climate change studies have highlighted shortcomings in the Canegro sugarcane model that could negatively influence the accuracy of predictions of climate change impacts.   Simulation of high temperature effects on phenology, photosynthesis and respiration are based on extrapolation of relationships derived from research conducted at present day temperature and vapour pressure deficit (VPD) regimes.  The simulation of elevated atmospheric CO₂ ([CO₂]) impacts on transpiration and photosynthesis are also based on theory untested in sugarcane.  The purpose of this study is to use recent research findings and insights  to improve the relevant algorithms, and to assess the performance of the new model under current and future climates.

 The paper will describe the proposed changes to the simulation of: leaf and tiller phenology; root, leaf and stalk growth rates; and photosynthesis and respiration, based on available results,  theories from the literature and approaches used in other sugarcane models.   The performance of the existing and new versions of the model will be evaluated by comparing simulations to observations of canopy cover, cane yield and sucrose yield from detailed growth analysis experiments conducted at four sites, in Australia (Ayr), Brazil (Piracicaba) and South Africa (La Mercy and Komatipoort).  Model performance will also be assessed by analysing sensitivity of simulated processes and yields to different levels of increased temperature, VPD and [CO₂] at the four sites.  A 30-year daily weather data record and [CO₂] of 360 ppm will form the baseline scenario at each site.  Future climate is represented by three scenarios consisting of current temperature records elevated by 3, 6 and 9 °C and [CO₂] at 720 ppm.   

 Further model and methodology weaknesses identified will be described, and  opportunities for future research aimed at addressing these will be outlined.