A Comparison of the Canopy Arthropod Communities of Coniferous and Broad-leaved Trees in the United Kingdom

Abstract

The canopy fauna of four coniferous tree species was compared with those of four deciduous broad-leaved species from the UK. Sampling was carried out using Pyrethrin knockdown and density and species richness data were standardized to 1 m2 ground area. Quantitative analyses confirm that the canopies of conifers and broad-leafs support defined but very different communities. For example, mean densities of arthropods were significantly higher for conifers ( P < 0.001) and when individuals were allocated to feeding guilds, conifers supported proportionately more scavenger/epiphyte feeders whereas broad-leaved trees were dominated by phytophages. The implications of these findings for forest dynamics and herbivore loads are considered. Both groups of trees are dominated by organisms with small body sizes; suggested reasons for this include microclimate and food resources available in the canopy. The species richness of epiphyte feeders and predators was comparable for conifers and broad-leaved trees, however the richness of herbivores was greater on the latter. Woodland specialist species were found in the conifer communities with Pinus sylvestris (Scots pine) supporting a particularly rich and dense fauna. The proportion of canopy specialist species, particularly epiphyte feeders, would be expected to increase with maturity of the trees. Although the communities differed from broad-leaved trees it can be concluded that conifers make valuable habitats for arthropods when grown in plantation and can enhance diversity where natural forest is not available.