Litterfall dynamics in Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula) stands in Estonia

•Average annual litter flux was similar for studied pine, spruce and birch stands.•Both stand age and site quality index were significant factors affecting the annual litter flux.•No significant relationship was established between stand basal area and litter flux.•For all tree species, the relative proportion of needles or leaves from in total annual litter flux declined with stand age.•The effect of weather conditions on the annual litter flux was revealed in continuously studied stands.