Background
The authors write that "peatland ecosystems are vast global repositories of organic matter, containing an estimated 455 Gt of carbon (Gorham, 1991)," and they suggest, therefore, that it is important to determine how they will likely respond to projected increases in the air's CO2 content.

What was done
Fenner et al. collected intact peat monoliths -- comprised predominantly of Sphagnum (S. subnitens Russ. and Warnst.) and Festuca ovina L., with small amounts of Juncus effusus L. and Polytrichum commune Hedw. -- in perfusion systems that allow for fine control of the water table and lateral water movements, which they maintained for approximately three years in Solardomes with atmospheric CO2 concentrations of ambient or ambient plus 235 ppm, while daily supplying the mini-ecosystems with synthetic rainwater that was comparable in volume and nutrient content to that received at the site from which the monoliths were extracted.

What was learned
At the end of their 3-year experiment, the seven UK researchers found that "species composition showed a shift from a Sphagnum-dominated community to one in which vascular monocotyledonous species dominated," as S. subnitens cover declined by 39% under elevated CO2, whereas J. effusus cover increased, from less than 1% in the control perfusion systems to 40% in the systems exposed to elevated CO2. Concomitantly, they found that "aboveground plant biomass showed a substantial increase under elevated CO2 (115%, P < 0.01) as did belowground biomass (96%, P < 0.01)." Furthermore, they report that "J. effusus roots were observed to be particularly thick, deep, and extensive under elevated CO2."

What it means
As the air's CO2 content continues to climb ever higher, so too should the carbon content of the planet's peatlands continue to rise -- and dramatically so -- especially if ecosystem productivity responds like it did in the monoliths studied by Fenner et al. The researchers themselves, however, suggest just the opposite; but their reason for doing so derives from their believing in the validity of the tremendous warming that is predicted to accompany the increase in atmospheric CO2 by the world's newest Nobel Peace Prize winner, i.e., the IPCC (and Al Gore). We feel a greater allegiance to sticking with what is more surely known, among which things are the results of Fenner et al.'s own experimentation.

Reference
Gorham, E. 1991. Northern peatlands: role in the carbon cycle and probable responses to climatic warming. Ecological Applications 1: 185-192.