Thinning is a routine forest management operation that changes tree spacing, number, and size distribution and affects the material flows between vegetation and the atmosphere. Here, using direct micrometeorological ecosystem‐scale measurements, we show that in a boreal pine forest, thinning decreases the deposition velocities of fine particles as expected but does not reduce the carbon sink, water vapor flux, or ozone deposition. The thinning decreased the all‐sided leaf area index from 8 to 6, and we suggest that the redistribution of sources and sinks within the ecosystem compensated for this reduction in foliage area. In the case of water vapor and O₃, changes in light penetration and among‐tree competition seem to increase individual transpiration rates and lead to larger stomatal apertures, thus enhancing also O₃ deposition. In the case of CO₂, increased ground vegetation assimilation and decreased autotrophic respiration seem to cancel out opposite changes in canopy assimilation and heterotrophic respiration. Current soil‐vegetation‐atmosphere transfer models should be able to reproduce these observations.

• Although there is increasing evidence of the temporal correlation between photosynthesis and soil CO₂ 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 CO₂ 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 CO₂ diffusivity on soil CO₂ efflux was taken into account. • Multi‐temporal correlations between photosynthesis and soil CO₂ efflux exist, and suggest that multiple biophysical drivers (i.e. photosynthesis, soil CO₂ 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.

Summary: The 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’ (CASSIA) 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.