ecologists no relation carbon dioxide
Free-Air Carbon dioxide Enrichment (FACE) is a method used by ecologists and plant biologists that raises the concentration of CO2 in a specified area and allows the response of plant growth to be measured. Experiments using FACE are required because most studies looking at the effect of elevated CO2 concentrations have been conducted in labs and where there are many missing factors including plant competition. Measuring the effect of elevated CO2 using FACE is a more natural way of estimating how plant growth will change in the future as the CO2 concentration rises in the atmosphere. FACE also allows the effect of elevated CO2 on plants that cannot be grown in small spaces (trees for example) to be measured. However, FACE experiments carry significantly higher costs relative to greenhouse experiments.Results
In 2004, a meta-analysis of 15 years of FACE studies, found the response to elevated CO2 using FACE only slightly increases yield in crop plants (5-7% in rice and 8% in wheat). These responses were lower than was expected from previous studies that measured the effect in labs or enclosures. This has important consequences as previous projections of food production have assumed that decreases in yield as a result of climate change would be offset by increases in yield due to elevated CO2.As of 2010, a more complete picture is emerging, with significant difference in response being observed for different plant species, water availabilities and the concentration of ozone. For example, the 2007-2010 Horsham FACE project (using wheat crops) in Victoria, Australia, found "The effect of eCO2 was to increase crop biomass at maturity by 20% and anthesis root biomass increased by 49%". This study also concludes that "a wide gene pool needs to be investigated to see if particular cultivars are able to respond more to eCO2". Increased atmospheric carbon dioxide has been found to reduce plant water use, and consequently, the uptake of nitrogen, so particularly benefiting crop yields in arid regions. The carbohydrate content of crops is increased from photosynthesis, but protein content is reduced due to lower nitrogen uptake. Legumes and their symbiotic "nitrogen fixing" bacteria appear to benefit more from increased carbon dioxide levels than most other species.
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