title: The effects of 11 yr of CO₂ enrichment on roots in a Florida scrub-oak ecosystem.
abstract: Uncertainty surrounds belowground plant responses to rising atmospheric CO₂ because roots are difficult to measure, requiring frequent monitoring as a result of fine root dynamics and long-term monitoring as a result of sensitivity to resource availability. We report belowground plant responses of a scrub-oak ecosystem in Florida exposed to 11 yr of elevated atmospheric CO₂ using open-top chambers. We measured fine root production, turnover and biomass using minirhizotrons, coarse root biomass using ground-penetrating radar and total root biomass using soil cores. Total root biomass was greater in elevated than in ambient plots, and the absolute difference was larger than the difference aboveground. Fine root biomass fluctuated by more than a factor of two, with no unidirectional temporal trend, whereas leaf biomass accumulated monotonically. Strong increases in fine root biomass with elevated CO₂ occurred after fire and hurricane disturbance. Leaf biomass also exhibited stronger responses following hurricanes. Responses after fire and hurricanes suggest that disturbance promotes the growth responses of plants to elevated CO₂. Increased resource availability associated with disturbance (nutrients, water, space) may facilitate greater responses of roots to elevated CO₂. The disappearance of responses in fine roots suggests limits on the capacity of root systems to respond to CO₂ enrichment.
authors.affiliation: Department of Biological Sciences, Old Dominion University, Norfolk, VA, 23529, USA.
authors.forename: Frank P
authors.initials: FP
authors.lastname: Day
authors.affiliation: Department of Biological Sciences, Old Dominion University, Norfolk, VA, 23529, USA.
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Schroeder
authors.affiliation: Office of Biological and Environmental Research, US Department of Energy, Washington, DC, 20585, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Stover
authors.affiliation: Department of Biological Sciences, Old Dominion University, Norfolk, VA, 23529, USA.
authors.forename: Alisha L P
authors.initials: ALP
authors.lastname: Brown
authors.affiliation: Southern Research Station, USDA Forest Service, Burlington, VT, 05405, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Butnor
authors.affiliation: Department of Biology, Chowan University, Murfreesboro, NC, 27855, USA.
authors.forename: John
authors.initials: J
authors.lastname: Dilustro
authors.affiliation: Department of Biological Sciences and the Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ, 86011, USA.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Hungate
authors.affiliation: Department of Biological Sciences and the Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ, 86011, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Dijkstra
authors.affiliation: Global Change Solutions, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Duval
authors.affiliation: ENSCO Inc., Melbourne, FL, 32940, USA.
authors.forename: Troy J
authors.initials: TJ
authors.lastname: Seiler
authors.affiliation: Smithsonian Environmental Research Center, Edgewater, MD, 21037, USA.
authors.forename: Bert G
authors.initials: BG
authors.lastname: Drake
authors.affiliation: Department of Biology, University of Central Florida, Orlando, FL, 32816, USA.
authors.forename: C Ross
authors.initials: CR
authors.lastname: Hinkle
mesh_terms: D001272:Atmosphere; D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism*; D055867:Cyclonic Storms; D017753:Ecosystem; D004777:Environment; D005390:Fires; D005431:Florida; D018515:Plant Leaves / Q000254:growth & development; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism; D029963:Quercus / Q000254:growth & development* / Q000378:metabolism; D014197:Trees / Q000254:growth & development* / Q000378:metabolism
chemical_list: D002245:Carbon Dioxide
keywords: CO2 enrichment; disturbance; ground-penetrating radar; minirhizotrons; root biomass; root closure; scrub-oak