Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites

Martin G. De Kauwe*, Belinda E. Medlyn, Sönke Zaehle, Anthony P. Walker, Michael C. Dietze, Ying Ping Wang, Yiqi Luo, Atul K. Jain, Bassil El-Masri, Thomas Hickler, David Wårlind, Ensheng Weng, William J. Parton, Peter E. Thornton, Shusen Wang, I. Colin Prentice, Shinichi Asao, Benjamin Smith, Heather R. Mccarthy, Colleen M. IversenPaul J. Hanson, Jeffrey M. Warren, Ram Oren, Richard J. Norby

*Corresponding author for this work

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    Abstract

    Elevated atmospheric CO2 concentration (eCO2) has the potential to increase vegetation carbon storage if increased net primary production causes increased long-lived biomass. Model predictions of eCO2 effects on vegetation carbon storage depend on how allocation and turnover processes are represented. 

    We used data from two temperate forest free-air CO2 enrichment (FACE) experiments to evaluate representations of allocation and turnover in 11 ecosystem models. 

    Observed eCO2 effects on allocation were dynamic. Allocation schemes based on functional relationships among biomass fractions that vary with resource availability were best able to capture the general features of the observations. Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes. Few models represent turnover processes mechanistically and there was wide variation in predictions of tissue lifespan. Consequently, models did not perform well at predicting eCO2 effects on vegetation carbon storage. 

    Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions; careful testing of allocation schemes; and synthesis of allocation and turnover data in terms of model parameters. Data from intensively studied ecosystem manipulation experiments are invaluable for constraining models and we recommend that such experiments should attempt to fully quantify carbon, water and nutrient budgets.

    Original languageEnglish
    Pages (from-to)883-899
    Number of pages17
    JournalNew Phytologist
    Volume203
    Issue number3
    DOIs
    Publication statusPublished - Aug 2014

    Bibliographical note

    Copyright the Author(s) 2014. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

    Keywords

    • Allocation
    • Carbon (C)
    • Climate change
    • Models
    • Phenology

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