A cost-effective system for injecting pure CO 2 into open top chambers: design and performance

Global average temperature is expected to rise between 0.2°C and 4.8°C by the end of the century, and globally atmospheric carbon dioxide concentration is expected to increase from a mean of 400 µmol mol -1 in 2013 to 550-650 µmol mol -1 within the next 50-80 years. Studies suggest there has already been an effect of warmer temperatures on grape growth and development, such as grape phenology, with harvest dates advancing and vintages becoming shorter over the past 30 years in Australia. Such changes create logistical problems for wineries and diminish grape quality. In addition, increasing carbon dioxide concentrations ([CO 2]) are likely to alter grape vine growth and development. Understanding the combined effect of elevated carbon dioxide concentration (e[CO 2]) and temperature together with their interactions on grape and wine qualities is necessary for industry adaption to future climate change. Therefore a system was developed to elevate [CO 2] to 650 µmol mol -1 and increase temperature by 2 °C around the grapevines in open top chambers (OTC) to simulate climate warming. The temporal and spatial distribution of CO 2 gas at the center of the OTC was maintained to within 72 µmol mol -1 standard deviation of the target (650 µmol mol -1 ), which is comparable to the distribution reported in Free Air CO 2 Enrichment (FACE) systems. The injection system described in this article consumed 60 g m -3 h -1 of CO 2 which is less than one-fifth of the CO 2 consumed by the Australian Grains Free Air CO 2 Enrichment system (318 g m -3 h -1 ) and a circular OTC (316 g m -3 h -1 ) used in a previous study as well as very similar to the consumption of the ForestFACE (50 g m -3 h -1 ). The cost-effective CO 2 injection system proposed here is therefore recommended for use inside OTCs in evaluating the effects of e[CO 2] in combination with elevated temperature in woody perennial crops.