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The effects of small-scale trait variability on regional-scale ecosystem behavior

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Diagram of soil precipitation

Earth has hundreds of thousands of species, each with different responses to climatic, edaphic, and other sources of variability. However, for regional or global studies, it is all but impossible to represent much of this diversity of behavior explicitly, both because it’s computationally infeasible and because not enough information about the landscape is available. Our group has studied how this aggregated behavior affects affect water and carbon fluxes at larger scales, which we have studied for various aspects of stomatal conductance, wildfire fuel moisture content and burned area, and more. We also use remote sensing and model-data fusion (data assimilation) to build better tools for studying this issue. We have mapped ‘effective ecosystem-scale’ ecosystem traits that integrate the aggregate behavior of the small-scale variability and represent differences in behavior at intermediate stand-scales. Most land surface and earth system models largely ignore this variability of behavior, instead parametrizing all vegetation of the same plant functional type similarly. Indeed, decades of modeling effort have focused on building more-detailed representations of ecosystem processes, but much less attention has been paid to correctly assigning ecosystem traits and their spatial variability. Our group has shown that this approach is counter-productive. In fact, simpler models make better predictions than ever-more complicated models, unless there is enough data and a robust approach to parametrize the more complicated models correctly. As an alternative, together with colleagues at JPL, the University of Edinburgh, and several other institutions, we have contributed to the development and use of the CARbon DAta MOdel fraMework (CARDAMOM), a terrestrial carbon cycle model that uses model-data fusion in combination with several remote sensing data streams to determine optimal representations of carbon pools, fluxes, and parameters across the more. Lastly, we are developing and testing alternative approaches that could be used to replace or enhance the decades-old plant functional type paradigm.

Selected Publications

Global net biome CO2 exchange predicted comparably well using parameter–environment relationships and plant functional types
Famiglietti, C.A., M. Worden, G.R. Quetin, T.L. Smallman, U. Dayal, A.A. Bloom, M. Williams, and A.G. Konings (2022). Global net biome CO2 exchange predicted comparably well using parameter–environment relationships and plant functional types. Global Change Biology, 29:2256-2273. 

Evapotranspiration frequently increases during droughts
Zhao, M., G.A., Y. Liu, and A.G. Konings (2022). Evapotranspiration frequently increases during droughts. Nature Climate Change, 12:1024-1030.

Canopy height and climate dryness parsimoniously explain spatial variation of unstressed stomatal conductance
Liu, Y., O. Flournoy, Q. Zhang, K.A. Novick. R.D. Koster, and A.G. Konings (2022). Geophysical Research Letters, 49:e2022GL099339.

Plant-water sensitivity regulates wildfire vulnerability
Rao, K., A.P. Williams, N.S. Diffenbaugh, M. Yebra, and A.G. Konings (2022). Nature Ecology and Evolution.

Global ecosystem-scale plant hydraulic traits retrieved using model-data fusion
Liu, Y., N.M. Holtzman, and A.G. Konings (2021). Hydrology and Earth System Science, 25:2399-2417.

Optimal model complexity for terrestrial carbon cycle prediction
Famiglietti, C.A., T.L. Smallman, P.A. Levine, S. Flack-Parin, G.R. Quetin, V. Meyer, N.C. Parazoo, S.G. Stettz, Y. Yang, D. Bonal, A.A. Bloom, M. Williams, and A.G. Konings (2021). Biogeosciences, 18:2727-2754.

Carbon flux variability from a relatively simple ecosystem model with assimilated data is consistent with terrestrial biosphere model estimates
Quetin G.R, A.A Bloom, K.W. Bowman, and A.G. Konings (2020). Journal of Advances in Modeling Earth Systems, 12: e2019MS001889.

Sensitivity of grassland productivity to aridity controlled by stomatal and xylem regulation
Konings, A. G., A.P. Williams, and P. Gentine (2017). Nature Geoscience, 10: 284-288.

Global variations in ecosystem scale isohydricity
Konings, A. G. and P. Gentine (2017). Global Change Biology,  23 (2): 891-905.