Nonstructural leaf carbohydrate dynamics of Pinus edulis during drought-induced tree mortality reveal role for carbon metabolism in mortality mechanism

Authors

  • Henry D. Adams,

    Corresponding author
    1. Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
    2. Biosphere 2, University of Arizona, Tucson, AZ, USA
    3. Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
    • Author for correspondence:

      Henry D. Adams

      Tel: +1 505 665 7661

      Email: adamshd@lanl.gov

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  • Matthew J. Germino,

    1. US Geological Survey, Forest and Rangeland Ecosystem Science Center, Boise, ID, USA
    2. Department of Biological Sciences, Idaho State University, Pocatello, ID, USA
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  • David D. Breshears,

    1. Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
    2. Biosphere 2, University of Arizona, Tucson, AZ, USA
    3. School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA
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  • Greg A. Barron-Gafford,

    1. Biosphere 2, University of Arizona, Tucson, AZ, USA
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  • Maite Guardiola-Claramonte,

    1. Hydrology and Water Resources, University of Arizona, Tucson, AZ, USA
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  • Chris B. Zou,

    1. Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK, USA
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  • Travis E. Huxman

    1. Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
    2. Biosphere 2, University of Arizona, Tucson, AZ, USA
    3. Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
    4. Center for Environmental Biology, University of California, Irvine, CA, USA
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Summary

  • Vegetation change is expected with global climate change, potentially altering ecosystem function and climate feedbacks. However, causes of plant mortality, which are central to vegetation change, are understudied, and physiological mechanisms remain unclear, particularly the roles of carbon metabolism and xylem function.
  • We report analysis of foliar nonstructural carbohydrates (NSCs) and associated physiology from a previous experiment where earlier drought-induced mortality of Pinus edulis at elevated temperatures was associated with greater cumulative respiration. Here, we predicted faster NSC decline for warmed trees than for ambient-temperature trees.
  • Foliar NSC in droughted trees declined by 30% through mortality and was lower than in watered controls. NSC decline resulted primarily from decreased sugar concentrations. Starch initially declined, and then increased above pre-drought concentrations before mortality. Although temperature did not affect NSC and sugar, starch concentrations ceased declining and increased earlier with higher temperatures.
  • Reduced foliar NSC during lethal drought indicates a carbon metabolism role in mortality mechanism. Although carbohydrates were not completely exhausted at mortality, temperature differences in starch accumulation timing suggest that carbon metabolism changes are associated with time to death. Drought mortality appears to be related to temperature-dependent carbon dynamics concurrent with increasing hydraulic stress in P. edulis and potentially other similar species.

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