Effects of vegetation management on plant and insect functional group composition in Quercus serrata secondary forests on the Musashino Terrace, Japan

Abstract

In this study, we investigated the influence of four vegetation management treatments (tree cutting, mowing and litter removal, removal of evergreen trees under the shrub layer, and abandonment) on the composition of plant and insect functional groups in Quercus serrata secondary forests on the Musashino Terrace, Japan. We performed a vegetation survey, monthly transect surveys, and an insect pitfall trap survey, and recorded 175 plant species and 271 insect species, which we then classified into eight plant functional groups (PFGs) and six insect functional groups (IFGs), respectively, using cluster analysis. Plant functional traits included Raunkiaer life form, leaf survival season, growth form, radicle form, pollination and seed dispersal syndromes, blooming season, fruiting season, and seed weight. PFGs were mainly classified according to seed dispersal and fruiting season. The PFG characterised by spring blooming and fruiting, small seeds, and hemicryptophytic form included herbaceous species that are typically found in managed secondary forests as well as many threatened species. Meanwhile, spring-blooming, deciduous plants included tree species typical of secondary forests, and endzoochorous evergreen trees included ornamental and garden trees. Insect functional traits included body size, larval feeding type, imago feeding type and season of imago appearance. IFGs were classified according to body size and larval feeding type. Among the IFGs, small folivores included Chrysomelidae and Symphyta; medium-sized herbivorous folivores (palynivores, nectivores, frugivores and xylophages) included Lycaenidae, Cerambycidae and Scarabaeidae; large folivores included Nymphalidae, Acrididae and Tettigoniidae; scavenging and dung-feeding insects included Scarabaeidae and Staphylinidae; and medium-sized insectivorous insects included Carabinae, Gryllidae and Vespinae. Ordination of the functional groups based on redundancy analysis indicated that PFGs were distributed along gradients of the forest floor environment, such as the number of fallen leaves accumulated on the ground surface and soil hardness, whereas IFGs were distributed along gradients of the tree layer environment, such as canopy openness. In terms of vegetation management effects, PFG composition was mainly influenced by mowing and litter removal, whereas IFG composition was mainly influenced by tree cutting and evergreen tree removal.