Reference
Day, F.P., Schroeder, R.E., Stover, D.B., Brown, A.L.P., Butnor, J.R., Dilustro, J., Hungate, B.A., Dijkstra, P., Duval, B.D., Seiler, T.J., Drake, B.G. and Hinkle, C.R. 2013. The effects of 11 years of CO2 enrichment on roots in a Florida scrub-oak ecosystem. New Phytologist 200: 778-787.
Background
The site of this study was the Kennedy Space Center on Merritt Island National Wildlife Refuge on the east coast of Florida, USA, where the soil is acidic, well-drained and nutrient-poor, and where the climate is subtropical with a wet season between late June and October and a dry season between April and early June. At this site, lightening-induced fire is the chief ecosystem disturbance, exhibiting a 7-15-year cycle, while other natural disturbances are periodic drought and severe weather from tropical storms and hurricanes.
What was done
In this particular study, Day et al. report the belowground root responses of a scrub-oak ecosystem, where half of the study's open-top chambers enclosing groups of the trees were exposed to eleven years of atmospheric CO2 enrichment to approximately 350 ppm above the ambient concentration. This they did by measuring fine root production, turnover and biomass using mini-rhizotrons, coarse root biomass using ground-penetrating radar, and total root biomass using soil cores.
What was learned
The twelve researchers report that "total root biomass was as much as five times greater than aboveground biomass in this system, reflecting the importance of belowground structures as a carbon reservoir." They also note that the belowground biomass was temporally dynamic and underwent natural cycles that are "affected by ecosystem disturbances in systems with strong disturbance regimes." More specifically, they state that "strong CO2 effects on fine root biomass were seen after disturbance by fire and hurricane during periods of recovery followed by periods in which CO2 effects diminished."
What it means
In the concluding words of Day et al., "elevated CO2 may enhance root growth following disturbance and potentially speed up the recovery." Indeed, it would appear that even following the massive aboveground destruction caused by both fires and hurricanes, atmospheric CO2 enrichment is able to bring scrub-oak ecosystems back from the brink, so to speak, to once again flourish, as the life-giving gas stimulates root production and the acquisition of needed-but-scarce soil nutrients.