How do we study the effect of CO2 on plants?

Dr. Bert Drake designed these open-top chambers in the 1980's to allow his team of researchers to regulate both the concentration of CO2 around wetland plants and the duration of CO2 exposure.

Mid-Atlantic Marsh

Fifteen marshland sites are being monitored, representing pure grass communities, pure sedge communites, and mixed communities. In each there are five chambers exposed to normal CO2, five exposed to elevated CO2, and five no-chamber control sites. These sites were established in 1986 and have been exposed to either normal ambient or elevated CO2 levels ever since.
    The species being studied belong to two photosynthetic types that represent most of the plant life on earth. The sedge, Scirpus olneyi, belongs to a class called C3 plants, which includes more than 95 percent of the plant species on earth. (Trees, for example, are also C3 plants.) C4 plants, such as the common marsh grass, Spartina patens, and other herbaceous plants, are abundant in arid, hot environments. They include such crop plants as sugar cane, corn, and soybeans, and are the second most prevalent photosynthetic type.

Florida Scrub Oak

Since May of 1996, SERC's CO2 lab has operated 16 open top chambers in a scrub oak ecosystem on the Merritt Island Wildlife Refuge, Cape Canaveral, Florida, at normal ambient or elevated (normal ambient plus 350 ppm) atmospheric CO2 in a long-term study of ecosystem carbon cycling. The chambers are large (3.5meters in diameter by 2.5 meters high) octagonal open top chambers.
    This study was initiated because we wanted to determine the effects of elevated CO2 on an ecosystem that could serve as a surrogate for a forest small enough to be contained within open top chambers not more than 4 meters tall. We were looking for vegetation which was woody, perennial, and deciduous, and that had a mature nutrient cycle. We found all of these features in the scrub oak of the Merritt Island Wildlife refuge in Florida, part of which is occupied by the Kennedy Space Center.