Measured and modeled biomass growth in relation to photosynthesis acclimation of a bioenergy crop (Reed canary grass) under elevated temperature, CO ₂ enrichment and different water regimes

The seasonal biomass growth and photosynthesis performance of a bioenergy crop, Reed canary grass (Phalaris arundinacea L.) under elevated temperature (ambient + 3.5 °C), CO ₂ enrichment (700 μmol mol ^-1) and different water regimes, was examined. To quantify the contributions of acclimated photosynthesis to biomass growth under the environmental treatments, a simplified model was parameterized to simulate the seasonal biomass accumulation of this bioenergy crop. As a result, we found that during the early growing periods, the photosynthesis, leaf development and above-ground biomass growth of the plants were enhanced under elevated temperature conditions, due to higher temperature sum for crop development compared to ambient temperature conditions. However, elevation of temperature resulted also in earlier senescence and lower total biomass of RCG at the final harvest, which effect was the most pronounced with low soil water table. As a comparison, CO ₂ enrichment increased significantly the leaf development, photosynthesis and total biomass growth over the whole growing season. Under the combined elevation of temperature and CO ₂, the acclimation of photosynthesis and total biomass of the plants at the final harvest was similar to those caused by elevated temperature alone. In general, high water table favored the photosynthesis and biomass growth of the plants. To conclude, the simplified model built for this bioenergy crop simulated well the dynamics of seasonal canopy photosynthesis and biomass growth, and with good accuracy. Meanwhile, the uncertainty of model was also discussed.