Data and R codes for Manuscript: The element loss from forested ecosystems is largely reflected by the so-called dissolved phase (20-60 nm and >60 nm) were identified using Field Flow Fractionation coupled with inductively coupled plasma mass spectrometry and an organic carbon detector for the size-resolved detection of Al, Si, P, Ca, Mg, Mn, Fe, Zn and organic C. Colloids accounted for up to 90-100% of total element concentrations, emphasizing the importance of colloids for element cycling. Element concentrations showed seasonal patterns in stream waters. These patterns, however, differed between the catchments with distinct soil groups: the catchments with dystrophic terrestrial soils exhibited peak flows in colloidal element concentrations during spring, while those with eutrophic terrestrial soils did during summer. By contrast, catchments with semiterrestrial soils showed season-unrelated, single peaks of high element export. Peak concentrations were also influenced by the climatic regime, which in turn impacted colloid abundance.