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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Improving Predictions of Heterotrophic Respiration

Ben Bond-Lamberty


18 July 2016

Estimating heterotrophic respiration at large scales: Challenges, approaches, and next steps.

The Science  
We proposed improving representation of heterotrophic respiration (HR) in Earth system models by grouping metabolism and flux characteristics across space and time.

The Impact
We argued for development of Decomposition Functional Types (DFTs), analogous to plant functional types (PFTs), for use in global models. We applied cluster analysis to produce example DFTs based on the global variability in 11 biotic and abiotic factors that influence decomposition processes.

Heterotrophic respiration (HR), the aerobic and anaerobic processes mineralizing organic matter, is a key carbon flux but one impossible to measure at scales significantly larger than small experimental plots. This impedes our ability to understand carbon and nutrient cycles, benchmark models, or reliably upscale point measurements. Given that a new generation of highly mechanistic, genomic-specific global models is not imminent, we suggest that a useful step to improve this situation is the development of Decomposition Functional Types (DFTs). Analogous to plant functional types (PFTs), DFTs would abstract and capture important differences in HR metabolism and flux dynamics, allowing modelers and experimentalists to efficiently group and vary these characteristics across space and time. We applied cluster analysis to show how annual HR can be broken into distinct groups associated with global variability in biotic and abiotic factors, and we demonstrated that these groups are distinct from, but complementary to, PFTs. In this position paper, we suggested priorities for next steps to build a foundation for DFTs in global models to provide the ecological and climate change communities with robust, scalable estimates of HR.

Renu Joseph, Daniel Stover, SC-23.1
Renu.Joseph@science.doe.gov (301-903-9237), Daniel.Stover@science.doe.gov (301-903-0289)
Ben Bond-Lamberty (PNNL), Forrest M. Hoffman (ORNL), and Jitendra Kumar (ORNL)
bondlamberty@pnnl.gov, hoffmanfm@ornl.gov, and kumarj@ornl.gov

This research is the product of a working group on heterotrophic respiration led by M. Harmon and sponsored by the National Science Foundation, which funded meeting and travel expenses. B. Bond-Lamberty was supported by Office of Science of the U.S. Department of Energy as part of the Terrestrial Ecosystem Sciences Program. The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830. R. Vargas and AD McGuire acknowledge support from the U.S. Department of Agriculture (2014-67003-22070) and U.S. Geological Survey, respectively. F.M. Hoffman and J. Kumar were supported by the Biogeochemistry–Climate Feedbacks (BGC Feedbacks) Scientific Focus Area and the Next Generation Ecosystem Experiments Tropics (NGEE-Tropics) Project, which are sponsored DOE Office of Science, BER, Regional & Global Climate Modeling and Terrestrial Ecosystem Science Programs in the Climate & Environmental Sciences Division. FMH and JK’s contributions were authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.

B. Bond-Lamberty, D. Epron, J. Harden, M. E. Harmon, F. M. Hoffman, J. Kumar, A. D. McGuire, and R. Vargas, “Estimating heterotrophic respiration at large scales: Challenges, approaches, and next steps.” Ecosphere 7, (2016). doi:10.1002/ecs2.1380. (Reference link)

Example cluster analyses delineating DFTs from 11 global climatic, edaphic, carbon flux, and topographic characteristics. Randomly colored maps show the (a) five and (b) 50 most-different land regions from simultaneous consideration of all 11 variables. Map (c ) is the 50-region map colored by three dominant, orthogonal PCA factors.

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