Environmental and Vegetative Controls on Soil CO2 Efflux in Three Semiarid Ecosystems
AuthorRoby, Matthew C.
Scott, Russell L.
Barron-Gafford, Greg A.
Hamerlynck, Erik P.
Moore, David J. P.
AffiliationUniv Arizona, Sch Nat Resources & Environm, Tucson, AZ 85721 USA
Univ Arizona, Sch Geog & Dev, Tucson, AZ 85721 USA
Univ Arizona, Coll Sci, Biosphere 2, Tucson, AZ 85721 USA
MetadataShow full item record
CitationRoby, M.C.; Scott, R.L.; Barron-Gafford, G.A.; Hamerlynck, E.P.; Moore, D.J.P. Environmental and Vegetative Controls on Soil CO2 Efflux in Three Semiarid Ecosystems. Soil Syst. 2019, 3, 6.
RightsCopyright © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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AbstractSoil CO2 efflux (F-soil) is a major component of the ecosystem carbon balance. Globally expansive semiarid ecosystems have been shown to influence the trend and interannual variability of the terrestrial carbon sink. Modeling F-soil in water-limited ecosystems remains relatively difficult due to high spatial and temporal variability associated with dynamics in moisture availability and biological activity. Measurements of the processes underlying variability in F-soil can help evaluate F-soil models for water-limited ecosystems. Here we combine automated soil chamber and flux tower data with models to investigate how soil temperature (T-s), soil moisture (theta), and gross ecosystem photosynthesis (GEP) control F-soil in semiarid ecosystems with similar climates and different vegetation types. Across grassland, shrubland, and savanna sites, theta regulated the relationship between F-soil and T-s, and GEP influenced F-soil magnitude. Thus, the combination of T-s, theta, and GEP controlled rates and patterns of F-soil. In a root exclusion experiment at the grassland, we found that growing season autotrophic respiration accounted for 45% of F-soil. Our modeling results indicate that a combination of T-s, theta, and GEP terms is required to model spatial and temporal dynamics in F-soil, particularly in deeper-rooted shrublands and savannas where coupling between GEP and shallow theta is weaker than in grasslands. Together, these results highlight that including theta and GEP in F-soil models can help reduce uncertainty in semiarid ecosystem carbon dynamics.
NoteOpen access journal
VersionFinal published version
SponsorsUSDA-ARSUnited States Department of Agriculture (USDA); U.S. Department of Energy Berkeley National Labs