Constraining long‐term model predictions for woody growth using tropical tree rings
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- Department of Ecology and Evolutionary Biology Cornell University Ithaca New York USA
- Forest Ecology &, Forest Management Group Wageningen University Wageningen The Netherlands
- Department of Plant Biology Institute of Biology University of Campinas, UNICAMP Campinas SP Brazil
- Department of Biological Sciences University of Notre Dame Notre Dame Indiana USA
- Department of Organismic and Evolutionary Biology Harvard University Cambridge Massachusetts USA
Abstract The strength and persistence of the tropical carbon sink hinges on the long‐term responses of woody growth to climatic variations and increasing CO 2 . However, the sensitivity of tropical woody growth to these environmental changes is poorly understood, leading to large uncertainties in growth predictions. Here, we used tree ring records from a Southeast Asian tropical forest to constrain ED2.2‐hydro, a terrestrial biosphere model with explicit vegetation demography. Specifically, we assessed individual‐level woody growth responses to historical climate variability and increases in atmospheric CO 2 (C a ). When forced with historical C a , ED2.2‐hydro reproduced the magnitude of increases in intercellular CO 2 concentration (a major determinant of photosynthesis) estimated from tree ring carbon isotope records. In contrast, simulated growth trends were considerably larger than those obtained from tree rings, suggesting that woody biomass production efficiency (WBPE = woody biomass production:gross primary productivity) was overestimated by the model. The estimated WBPE decline under increasing C a based on model‐data discrepancy was comparable to or stronger than (depending on tree species and size) the observed WBPE changes from a multi‐year mature‐forest CO 2 fertilization experiment. In addition, we found that ED2.2‐hydro generally overestimated climatic sensitivity of woody growth, especially for late‐successional plant functional types. The model‐data discrepancy in growth sensitivity to climate was likely caused by underestimating WBPE in hot and dry years due to commonly used model assumptions on carbon use efficiency and allocation. To our knowledge, this is the first study to constrain model predictions of individual tree‐level growth sensitivity to C a and climate against tropical tree‐ring data. Our results suggest that improving model processes related to WBPE is crucial to obtain better predictions of tropical forest responses to droughts and increasing C a . More accurate parameterization of WBPE will likely reduce the stimulation of woody growth by C a rise predicted by biosphere models.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 2229933
- Journal Information:
- Global Change Biology, Journal Name: Global Change Biology Vol. 30 Journal Issue: 1; ISSN 1354-1013
- Publisher:
- Wiley-BlackwellCopyright Statement
- Country of Publication:
- United Kingdom
- Language:
- English
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