Fine-root respiration in a loblolly pine (Pinus taeda L.) forest exposed to elevated CO2 and N fertilization

John E. Drake, Paul C. Stoy, Robert B. Jackson, Evan H. Delucia

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    63 Citations (Scopus)

    Abstract

    Forest ecosystems release large amounts of carbon to the atmosphere from fine-root respiration (Rr), but the control of this flux and its temperature sensitivity (Q10) are poorly understood. We attempted to: (1) identify the factors limiting this flux using additions of glucose and an electron transport uncoupler (carbonyl cyanide m-chlorophenylhydrazone); and (2) improve yearly estimates of Rr by directly measuring its Q 10in situ using temperature-controlled cuvettes buried around intact, attached roots. The proximal limits of Rr of loblolly pine (Pinus taeda L.) trees exposed to free-air CO2 enrichment (FACE) and N fertilization were seasonally variable; enzyme capacity limited Rr in the winter, and a combination of substrate supply and adenylate availability limited Rr in summer months. The limiting factors of Rr were not affected by elevated CO2 or N fertilization. Elevated CO2increased annual stand-level Rr by 34% whereas the combination of elevated CO2 and N fertilization reduced Rr by 40%. Measurements of in situ Rr with high temporal resolution detected diel patterns that were correlated with canopy photosynthesis with a lag of 1 d or less as measured by eddy covariance, indicating a dynamic link between canopy photosynthesis and root respiration. These results suggest that Rr is coupled to daily canopy photosynthesis and increases with carbon allocation below ground.
    Original languageEnglish
    Pages (from-to)1663-1672
    Number of pages10
    JournalPlant Cell and Environment
    Volume31
    Issue number11
    DOIs
    Publication statusPublished - 2008

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