Effect of global warming on vines

The aim of this project was to determine what the combined effect of elevated temperature and Carbon dioxide (CO2) levels are on vines, over multiple seasons.

Project layout: 
-          An open top chamber (OTC) facility was established in a mature Shiraz vineyard in Australia;
-          An elevated CO2 and elevated temperature treatment could be applied to the chamber;
-          The effect of elevated temperature and CO2 could be studied individually and the experimental design also studied their interaction;
-          The treatment simulated what climate is expected to be in 2075, namely a 2°C increase in temperature and an increase of 650ppm CO2 in the air;
-          Phenology and leaf physiology/photosynthesis were studied;
-          Data was collected over three seasons.

-          Higher temperatures alone affected phenology from the first season of the trial. Phenology was significantly advanced;
-          Elevated CO2 levels alone, only started affecting phenology in the third season of the trial.
-          The combination of higher temperatures plus higher CO2 levels showed phenological advances similar to that of the elevated temperatures only treatment;
-          Warmer temperatures alone did not particularly affect leaf physiology/photosynthesis;
-          Strong interactions existed between elevated temperatures combined with elevated CO2 levels. This treatment showed higher rates of photosynthesis compared to only elevated CO2.

Significance of the study
Previous studies have proven that elevated temperatures and elevated CO2 levels individually affect vine physiology and maturity. This project however showed that if both these variables increase at the same time, the effect on vines is more exacerbated. This means that the effect of global warming may affect vineyards much more than anticipated in earlier studies that only considered one of these variables at a time. Further studies need to investigate the effect of increased photosynthesis on carbohydrate availability.

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