The body-size distribution of arboreal collembolans in relation to the vertical structure of a Japanese cedar plantation

Collembolans are among the most abundant microarthropods in the aboveground parts of forest ecosystems, but little is known about their life-history traits compared with those of the soil-dwelling collembolans. The life-history traits of arboreal collembolans, as well as their abundances, are expected to be influenced by the vertical structure of a forest. We analyzed the body-size distributions of dominant arboreal species in relation to the vertical structure of the forest. The small individuals of the three arboreal species that inhabit both the canopy and soil litter (Xenylla brevispina, Tomocerus cuspidatus, and Sphyrotheca multifasciata) appeared continuously from spring to autumn in the soil litter, whereas those in the canopy litter were found during a particular period, only in July. These individuals tended to be larger in the canopy litter than in the soil litter, and in particular, T. cuspidatus grew to become significantly larger in the canopy. The mean body size of the most abundant migrating species (X. brevispina) increased gradually from the soil to the upper canopy, whereas strict arboreal species (Entomobrya sp.) had no significant trend in the relationship between body size and the height above ground level. We concluded that the life-history traits of arboreal collembolans were influenced by the vertical structure of the forest.