title: Stored carbon partly fuels fine-root respiration but is not used for production of new fine roots.
abstract: The relative use of new photosynthate compared to stored carbon (C) for the production and maintenance of fine roots, and the rate of C turnover in heterogeneous fine-root populations, are poorly understood. We followed the relaxation of a (13)C tracer in fine roots in a Liquidambar styraciflua plantation at the conclusion of a free-air CO(2) enrichment experiment. Goals included quantifying the relative fractions of new photosynthate vs stored C used in root growth and root respiration, as well as the turnover rate of fine-root C fixed during [CO(2)] fumigation. New fine-root growth was largely from recent photosynthate, while nearly one-quarter of respired C was from a storage pool. Changes in the isotopic composition of the fine-root population over two full growing seasons indicated heterogeneous C pools; < 10% of root C had a residence time < 3 months, while a majority of root C had a residence time > 2 yr. Compared to a one-pool model, a two-pool model for C turnover in fine roots (with 5 and 0.37 yr(-1) turnover times) doubles the fine-root contribution to forest NPP (9-13%) and supports the 50% root-to-soil transfer rate often used in models.
authors: Department of Biological Sciences, University of Illinois at Chicago (UIC), Chicago, IL, 60607, USA.
authors: Douglas J
authors: DJ
authors: Lynch
authors: Argonne National Laboratory, Biosciences Division, 9700 S. Cass Avenue, Argonne, IL, 60439, USA.
authors: Roser
authors: R
authors: Matamala
authors: Oak Ridge National Laboratory, Climate Change Science Institute and Environmental Sciences Division, One Bethel Valley Road, Oak Ridge, TN, 37831, USA.
authors: Colleen M
authors: CM
authors: Iversen
authors: Oak Ridge National Laboratory, Climate Change Science Institute and Environmental Sciences Division, One Bethel Valley Road, Oak Ridge, TN, 37831, USA.
authors: Richard J
authors: RJ
authors: Norby
authors: Department of Biological Sciences, University of Illinois at Chicago (UIC), Chicago, IL, 60607, USA.
authors: Miquel A
authors: MA
authors: Gonzalez-Meler
mesh_terms: D002244:Carbon / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000494:pharmacology; D002247:Carbon Isotopes; D019069:Cell Respiration / Q000187:drug effects; D031317:Liquidambar / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D008954:Models, Biological; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development* / Q000502:physiology*
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D002244:Carbon
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