title: On the multi-temporal correlation between photosynthesis and soil CO2 efflux: reconciling lags and observations.
abstract: Although there is increasing evidence of the temporal correlation between photosynthesis and soil CO(2) efflux, no study has so far tested its generality across the growing season at multiple study sites and across several time scales. Here, we used continuous (hourly) data and applied time series analysis (wavelet coherence analysis) to identify temporal correlations and time lags between photosynthesis and soil CO(2) efflux for three forests from different climates and a grassland. Results showed the existence of multi-temporal correlations at time periods that varied between 1 and 16 d during the growing seasons at all study sites. Temporal correlations were strongest at the 1 d time period, with longer time lags for forests relative to the grassland. The multi-temporal correlations were not continuous throughout the growing season, and were weakened when the effect of variations in soil temperature and CO(2) diffusivity on soil CO(2) efflux was taken into account. Multi-temporal correlations between photosynthesis and soil CO(2) efflux exist, and suggest that multiple biophysical drivers (i.e. photosynthesis, soil CO(2) diffusion, temperature) are likely to coexist for the regulation of allocation and transport speed of carbon during a growing season. Future studies should consider the multi-temporal influence of these biophysical drivers to investigate their effect on the transport of carbon through the soil-plant-atmosphere continuum.
authors: Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Baja California, Mexico.
authors: Rodrigo
authors: R
authors: Vargas
authors: Department of Environmental Science Policy and Management, University of California, Berkeley, CA, USA.
authors: Dennis D
authors: DD
authors: Baldocchi
authors: Institute of Ecology, University of Innsbruck, Innsbruck, Austria.
authors: Michael
authors: M
authors: Bahn
authors: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors: Paul J
authors: PJ
authors: Hanson
authors: Department of Forestry, University of Missouri, Columbia, MO, USA.
authors: Kevin P
authors: KP
authors: Hosman
authors: Department of Forest Science, University of Helsinki, Helsinki, Finland.
authors: Liisa
authors: L
authors: Kulmala
authors: Department of Forest Science, University of Helsinki, Helsinki, Finland.
authors: Jukka
authors: J
authors: Pumpanen
authors: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors: Bai
authors: B
authors: Yang
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