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Annual basal area increment and growth duration of Pinus taeda in response to eight years of free-air carbon dioxide enrichment

Authors

  • DAVID J. P. MOORE,

    1. Program in Ecology and Evolutionary Biology, University of Illinois at Urbana – Champaign, Urbana, IL 61801, USA,
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    • 1Present address: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80301, USA.

  • SUSANNE AREF,

    1. Department of Statistics, University of Illinois at Urbana – Champaign, Urbana, IL 61801, USA,
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    • 2Present address: Department of Statistics, Virginia Polytechnic Institute and State University Blacksburg, VA 24061, USA.

  • RINGO M. HO,

    1. Department of Statistics, University of Illinois at Urbana – Champaign, Urbana, IL 61801, USA,
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    • 3Present address: Department of Psychology, McGill University, Montreal, QC, Canada, H3A 1B1.

  • JEFFREY S. PIPPEN,

    1. Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA,
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  • JASON G. HAMILTON,

    1. Department of Biology, Ithaca College, Ithaca, NY 14850, USA,
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  • EVAN H. DE LUCIA

    1. Department of Plant Biology, University of Illinois at Urbana – Champaign, Urbana, IL 61801, USA
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Evan DeLucia, tel. +217 333 3261, fax +217 244 7246, e-mail: delucia@uiuc.edu

Abstract

Rising CO2 is predicted to increase forest productivity, although the duration of the response and how it might be altered by variation in rainfall, temperature and other environmental variables are not well understood. We measured the basal area of rapidly growing Pinus taeda trees exposed to free-air CO2 enrichment for 8 years and used these measurements to estimate monthly and annual growth. We used these measurements in a statistical model to estimate the start and end of growth in each year. Elevated CO2 increased the basal area increment (BAI) of trees by 13–27%. In most years, exposure to elevated CO2 increased the growth rate but not the duration of the active growth period. With the exception of 1 year following an extreme drought and a severe ice storm, BAI was positively correlated with the amount of rainfall during the active growth period. The interannual variation in the relative enhancement of BAI caused by elevated CO2 was strongly related to temperature and rainfall, and was greatest in years with high vapor pressure deficit. There was no evidence of a systematic reduction in the stimulation of growth during the first 8 years of this experiment, suggesting that the hypothesized limitation of the CO2 response caused by nitrogen availability has yet to occur.

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