PARENT SESSION
Poster Session #45: Elevated CO₂ I.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Response of roots to five years of exposure to elevated atmospheric CO₂ in an oak-scrub ecosystem in Florida.

DAY, FRANK^*,1, PAGEL, ALISHA¹, HARTWIG, CARMONY¹, HERBERT, BRANDON¹, DILUSTRO, JOHN¹, ¹ Old Dominion University, Norfolk, VA

ABSTRACT- Elevated atmospheric CO₂ has been observed to have a fertilization effect on above and belowground growth of plants. A persistent question associated with these observations is "what is the duration of these responses?" We have investigated the effects of elevated carbon dioxide on fine root growth using open top chambers with both ambient and elevated (700 ppm) CO₂ treatments in an oak-scrub ecosystem at Kennedy Space Center, Florida for more than 5 years now. The system was burned prior to the start of the study. Minirhizotron tubes were installed in each elevated and control chamber to allow observation of roots. Each tube was sampled for root length density (mm cm^-2) every three months. After 5 years of continuous exposure to elevated CO₂ levels, fine root densities in the elevated chambers continue to be higher than in the ambient chambers. However, the relative magnitude of the response to elevated CO₂ the past 3 years (less than 30 % increase in root density) has been considerably less than the response during the first two years of the study (181 % increase in root density in December 1997). The results suggest that ambient and elevated chambers may be approaching closure of the root systems following the burn, but due to CO₂ fertilization, the elevated chambers got a head start.

KEY WORDS: fine roots, CO₂, oak-scrub