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Summary• 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.

SummaryThe control of tree growth vs environment by carbon sources or sinks remains unresolved although it is widely studied. This study investigates growth of tree components and carbon sink-source dynamics at different temporal scales.We constructed a dynamic growth model 'carbon allocation sink source interaction' (CAS-SIA) that calculates tree-level carbon balance from photosynthesis, respiration, phenology and temperature-driven potential structural growth of tree organs and dynamics of stored nonstructural carbon (NSC) and their modifying influence on growth. With the model, we tested hypotheses that sink demand explains the intra-annual growth dynamics of the meristems, and that the source supply is further needed to explain year-to-year growth variation.The predicted intra-annual dimensional growth of shoots and needles and the number of cells in xylogenesis phases corresponded with measurements, whereas NSC hardly limited the growth, supporting the first hypothesis. Delayed GPP influence on potential growth was necessary for simulating the yearly growth variation, indicating also at least an indirect source limitation.CASSIA combines seasonal growth and carbon balance dynamics with long-term source dynamics affecting growth and thus provides a first step to understanding the complex processes regulating intra-and interannual growth and sink-source dynamics.

R soil is a fraction of R eco and theoretically must be lower than R eco R eco was not consistently higher than R soil from daily to annual scales We discuss issues with current practices influencing under or overestimation of R eco and R soil Flux networks need a better integration of spatial and temporal variability of R eco and R soil