ARS | Publication request: EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON ROOT BIOMASS PRODUCTION ARE MEDIATED BY PLANT COMPETITION

Submitted to: Ecological Society of America Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 7, 2005
Publication Date: August 7, 2005
Citation: Pritchard, S., Runion, G.B., Prior, S.A., Davis, M., Mitchell, R., Rogers Jr, H.H. 2005. Effects of elevated atmospheric co2 on root biomass production are mediated by plant competition [abstract]. 90th Ecological Society of America Meetings.

Technical Abstract: Isolated plants grown in CO2-enriched atmospheres almost always grow bigger or more numerous roots. Little is known, however, regarding the effects of CO2-enrichment on root growth of plants growing in competition with other species. We established an outdoor facility using open top field chambers (OTCs) to examine the effects of elevated atmospheric CO2 (ambient + 365 ppm) on root biomass in artificially constructed communities of five early successional forest species: (1) a C3 evergreen conifer (longleaf pine, Pinus palustris); (2) a C4 monocotyledonous bunch grass (wiregrass, Aristida stricta); (3) a C3 broadleaf tree (sand post oak, Quercus margaretta); (4) a C3 perennial herbaceous legume (rattlebox, Crotalaria rotundifolia); and (5) an herbaceous C3 dicotyledonous perennial (butterfly weed, Asclepias tuberosa). A combination of soil coring and excavation was used to sample roots upon termination of a three year study. Total root biomass (0-60 cm) was 49% greater in CO2-enriched plots compared to controls. A 72% stimulation of longleaf pine root biomass by elevated CO2 explained this response. Total biomass of oak roots was unaffected. Data suggested that exposure to high CO2 decreased root biomass of wiregrass (-36%; P=0.02), rattlebox (-43%; P=0.16), and butterfly weed (-52%; P=0.11). We found similar patterns of shoot biomass production in which longleaf pine realized the greatest stimulation of shoot growth and rattlebox and butterfly weed biomass decreased. Results indicate the importance of competition for mediating plant responses to rising atmospheric CO2 concentrations.