Herbivory by insects on oak trees in pure stands compared with paired mixtures.
Herbivorous insect communities were studied on oak (Quercus petraea) trees in pure stands of oak or in mixtures with alder (Alnus glutinosa), pine (Pinus sylvestris) or spruce (Picea abies) at sites in Lancashire, UK. Censuses were made of the major groups of leaf-feeding insects from late May to September in 1984-87. Stand characteristics were measured in December 1986. The insect species found included 3 species each of Curculionidae and Typhlocybinae and 1 species each of Cicadellidae, Aphididae, Geometridae, Gracillariidae and Nepticulidae. The density of all herbivore groups on oaks was greatest in the oak/alder mixture and least in the oak/spruce mixture. Visible leaf damage varied according to herbivore group, level in canopy and whether the stand was pure or mixed.