ARS | Publication request: Endogenous circadian regulation of carbon dioxide exchange in terrestrial ecosystems

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2012
Publication Date: June 1, 2012
Citation: Resco, V., Goulden, M., Ogle, K., Richardson, A.D., Davidson, E.A., Hollinger, D.Y., Alday, J.G., Barron-Gafford, G.A., Carrara, A., Kowalski, A.S., Oechel, W.C., Reverter, B.R., Scott, R.L., Varner, R.K., Diaz-Sierra, R., Moreno, J.M. 2012. Endogenous circadian regulation of carbon dioxide exchange in terrestrial ecosystems. Global Change Biology. 18:1956-1970. doi: 10.1111/j.1365-2486.2012.02664.x

Interpretive Summary: We tested one of the major assumptions underlying studies on the exchange of carbon dioxide between terrestrial ecosystems and the atmosphere: that daily fluctuations in the net exchange of carbon dioxide are driven almost exclusively by the immediate physiological responses to changes in environmental factors like light, humidity and temperature. However, it is increasingly recognized that photosynthesis may also vary over time in the absence of variation in external forcing because of internal plant controls from the circadian clock. We analyzed observations of carbon dioxide exchange recorded at sites around the world. We found large daily fluctuations in ecosystem carbon exchange even after removing variation in the physical environment across a wide-variety of ecosystems. This analysis poses a new paradigm for understanding controls on carbon dioxide exchange of terrestrial ecosystems.

Technical Abstract: We tested the hypothesis that diurnal changes in terrestrial CO2 exchange are driven exclusively by the direct effect of the physical environment on plant physiology. We failed to corroborate this assumption, finding instead large diurnal fluctuations in whole ecosystem carbon assimilation across a range of ecosystem types even after removing variation in the physical environment. Our findings highlight the widespread occurrence of rhythmic, daily oscillations in carbon assimilation that are synchronized with the mean variation in the physical environment but driven by endogenous processes, and argue for consideration of a new paradigm on the physiological controls on terrestrial ecosystem CO2 exchange.