Date of Award

Spring 2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Program/Concentration

Ecological Sciences

Committee Director

Frank P. Day

Committee Member

Joseph Rule

Committee Member

Kneeland Nesius

Abstract

A major gap in whole-plant ecology lies with our understanding of root system growth, function and distribution. Large belowground structures, in addition to fine roots, are of particular interest because of their role in carbon sequestration. Non-destructive methods, including ground-penetrating radar (GPR) and minirhizotron observation tubes, were used to investigate effects of elevated CO2 on root biomass, dynamics (productivity, mortality, and turnover), root persistence and architecture in a fire dominated scrub-oak ecosystem. Open-top chambers have been exposed to elevated atmospheric CO2 for the past eleven years at Kennedy Space Center, Florida. No significant sustained CO2 treatment effects were observed in fine root length density, due to root closure. Root density at lower depths increased to match abundance levels observed in the upper portions of the soil profile. CO2 significantly affected fine root production, mortality, and turnover during the early years of fumigation; however, this effect disappeared as fine root closure occurred. Survivorship analysis suggested the smallest fine root size classes (2. Overall, 86% of the total biomass was belowground with 78% allocated to coarse roots and 22% to fine roots. Coarse root architecture determinations confirmed the complexity and abundance of large belowground structures in this system. Large roots with sharp angles or that transverse the study areas were most likely to be observed in the GPR images. Large root burls were readily visualized in the GPR based architecture models. The results suggest that coarse roots may play a large role in the sequestration of carbon belowground in scrub-oak ecosystems, thus having implications to carbon dynamics, CO2 treatment memory, and plant regeneration following disturbances such as fire.

DOI

10.25777/cac7-n592

ISBN

9780549040972

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