Date of Award

Summer 2011

Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences


Ecological Sciences

Committee Director

Frank P. Day

Committee Member

Rebecca D. Bray

Committee Member

G. Richard Whittecar


A Florida (USA) scrub-oak ecosystem was exposed to elevated atmospheric CO2 in open-top chambers from 1996-2007. Minirhizotrons and ground-penetrating radar (GPR) were used to measure fine root (< 2 mm diameter) and coarse root (> 5 mm diameter) biomass, respectively. After 11 years of CO2 enrichment, there was a trend of greater total root biomass under elevated CO2. Fine root biomass exhibited a pattern of recovery and steady state throughout the study, with significant CO2 stimulation observed only after disturbance. Greater root biomass under elevated CO2 during recovery periods could result in greater carbon inputs belowground, alteration of the soil carbon cycle, and faster ecosystem recovery. At the end of the study, a greater proportion of fine root biomass was found deeper in the soil in plots exposed to elevated CO2. The shift of biomass deeper in the soil and pattern of recovery and steady state suggest a limit on the soils' capacity to support fine roots. The dominant plants were not limited by water or nutrients, indicating that root responses to CO2 enrichment were likely constrained by soil resource space.