Leveraging the signature of heterotrophic respiration on atmospheric CO 2 for model benchmarking

Basile, Samantha J.; Lin, Xin; Wieder, William R.; Hartman, Melannie D.; Keppel-Aleks, Gretchen

Spatial and temporal variations in atmospheric carbon dioxide (inline-formulaCO2) reflect large-scale net carbon exchange between the atmosphere and terrestrial ecosystems. Soil heterotrophic respiration (HR) is one of the component fluxes that drive this net exchange, but, given observational limitations, it is difficult to quantify this flux or to evaluate global-scale model simulations thereof. Here, we show that atmospheric inline-formulaCO2 can provide a useful constraint on large-scale patterns of soil heterotrophic respiration. We analyze three soil model configurations (CASA-CNP, MIMICS, and CORPSE) that simulate HR fluxes within a biogeochemical test bed that provides each model with identical net primary productivity (NPP) and climate forcings. We subsequently quantify the effects of variation in simulated terrestrial carbon fluxes (NPP and HR from the three soil test-bed models) on atmospheric inline-formulaCO2 distributions using a three-dimensional atmospheric tracer transport model. Our results show that atmospheric inline-formulaCO2 observations can be used to identify deficiencies in model simulations of the seasonal cycle and interannual variability in HR relative to NPP. In particular, the two models that explicitly simulated microbial processes (MIMICS and CORPSE) were more variable than observations at interannual timescales and showed a stronger-than-observed temperature sensitivity. Our results prompt future research directions to use atmospheric inline-formulaCO2, in combination with additional constraints on terrestrial productivity or soil carbon stocks, for evaluating HR fluxes.

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Basile, Samantha J. / Lin, Xin / Wieder, William R. / et al: Leveraging the signature of heterotrophic respiration on atmospheric CO2 for model benchmarking. 2020. Copernicus Publications.

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