Emergent climate and CO2 sensitivities of net primary productivity in ecosystem models do not agree with empirical data in temperate forests of eastern North America |
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| Authors: | Christine R Rollinson Yao Liu Ann Raiho David J P Moore Jason McLachlan Daniel A Bishop Alex Dye Jaclyn H Matthes Amy Hessl Thomas Hickler Neil Pederson Benjamin Poulter Tristan Quaife Kevin Schaefer Jörg Steinkamp Michael C Dietze |
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| Affiliation: | 1. Department of Earth & Environment, Boston University, Boston, MA, USA;2. Morton Arboretum, Lisle, IL, USA;3. School of Natural Resources, University of Arizona, Tucson, AZ, USA;4. Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA;5. Havard Forest, Petersham, MA, USA;6. Department of Geology and Geography, West Virginia University, Morgantown, WV, USA;7. Department of Biological Sciences, Wellesley College, Wellesley, MA, USA;8. Senkenberg Biodiversity and Climate Research Centre (BiK‐F), Frankfurt am Main, Germany;9. Department of Physical Geography and Geosciences, Goethe University, Frankfurt am Main, Germany;10. Biospheric Science Laboratory, NASA Goodard Space Flight Center, Greenbelt, MD, USA;11. Institute on Ecosystem and Department of Ecology, Montana State University, Bozeman, MT, USA;12. Department of Meteorology, University of Reading, Reading, UK;13. National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA |
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| Abstract: | Ecosystem models show divergent responses of the terrestrial carbon cycle to global change over the next century. Individual model evaluation and multimodel comparisons with data have largely focused on individual processes at subannual to decadal scales. Thus far, data‐based evaluations of emergent ecosystem responses to climate and CO2 at multidecadal and centennial timescales have been rare. We compared the sensitivity of net primary productivity (NPP) to temperature, precipitation, and CO2 in ten ecosystem models with the sensitivities found in tree‐ring reconstructions of NPP and raw ring‐width series at six temperate forest sites. These model‐data comparisons were evaluated at three temporal extents to determine whether the rapid, directional changes in temperature and CO2 in the recent past skew our observed responses to multiple drivers of change. All models tested here were more sensitive to low growing season precipitation than tree‐ring NPP and ring widths in the past 30 years, although some model precipitation responses were more consistent with tree rings when evaluated over a full century. Similarly, all models had negative or no response to warm‐growing season temperatures, while tree‐ring data showed consistently positive effects of temperature. Although precipitation responses were least consistent among models, differences among models to CO2 drive divergence and ensemble uncertainty in relative change in NPP over the past century. Changes in forest composition within models had no effect on climate or CO2 sensitivity. Fire in model simulations reduced model sensitivity to climate and CO2, but only over the course of multiple centuries. Formal evaluation of emergent model behavior at multidecadal and multicentennial timescales is essential to reconciling model projections with observed ecosystem responses to past climate change. Future evaluation should focus on improved representation of disturbance and biomass change as well as the feedbacks with moisture balance and CO2 in individual models. |
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| Keywords: | climate change climate sensitivity ecosystem model emergent response model‐data comparison net primary productivity paleoecology tree rings |
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