PARENT SESSION
Poster Session 30: Soil Ecology.

Wednesday, August 4 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

The influence of elevated CO₂ and soil depth on fine root dynamics in a Florida oak-scrub ecosystem.

Stover, Daniel^*,1, Day, Frank¹, Bacalan, Vincent¹, Drake, Bert², Pagel, Alisha¹, ¹ Old Dominion University, Norfolk, VA, USA² Smithsonian Environmental Research Center, Edgewater, MD, USA

ABSTRACT- Fine root dynamics (i.e. turnover and mortality) have the potential to influence the sequestration of carbon into the soil. However, few studies have partitioned such measurements along a soil profile. Minirhizotron tubes were utilized to monitor the effects of elevated (700 ppm) and ambient (350 ppm) atmospheric CO₂ on the rhizosphere in an oak-scrub ecosystem at Kennedy Space Center, Florida. Using four 25 cm depth categories, fine root density, mortality, productivity and turnover were measured and compared to overall combined treatments. Early root length density treatment effects have disappeared; however, a general trend of decreasing density is observed with increasing depth along the soil profile. This response is also inversely related to the relative soil moisture as measured by time domain reflectometry. Fine root dynamics also follow this general trend with the 25-50 cm depth class have the highest dynamic response to all variables measured. In addition, all measured variables appear to be increasing over time. Greater production in the ambient treatment compared to the elevated suggests that our system is approaching root closure and might begin to deploy roots deeper into the rhizosphere or that turnover is masking any further treatment effects in the elevated chambers.

Key words: minirhizotron, root, carbon dioxide, soil profile