ARTHROPOD RAIN IN A TEMPERATE FOREST: INTENSITY AND COMPOSITION

Abstract One of the factors regulating the functioning of detrital food webs can be a supplementary input of carbon and nutrients from aboveground. The intensity of the “arthropod rain”, i.e., various invertebrates falling from the tree crowns in temperate forests, remains unquantified, although the importance of this phenomenon for the functioning of aquatic ecosystems is relatively well documented. The study was carried out in two forest stands during the whole growing season. Arthropods falling from tree crowns were sampled using custom-made traps that separated dead and living animals. In addition to the arthropod rain, the amounts of plant litter and arthropod frass collected by the traps were measured. The intensity of the arthropod rain fluctuated with time but remained relatively constant from May to October, averaging 19 mg dry weight m −2 day -1 . The taxonomic composition of the arthropod rain was diverse and included more than 60 families. Collembolans and mites were the most abundant animals, whereas Diptera, Coleoptera, and Hemiptera, including aphids, were the most important groups in terms of biomass. Some of these animals can be easy prey for soil predators. Moreover, approx. 28% of the total arthropod rain is formed by dead animals and exuviae; this fraction can be readily consumed by soil decomposers. The arthropod rain can be a non-negligible energy channel subsidizing detrital food webs, although its functional significance requires further investigation.