The Energy Relations of Defoliating Insects in a Hazel Coppice

Studies into the energy relations of terrestrial communities have figured in research literature for about 12 years, the first such investigation being that of Golley (1960) who analysed an old-field food chain. The same or similar habitats have since provided study areas for a succession of workers, some of whom (e.g. Wiegert 1964, 1965) have measured energy flow in the herbivorous insects of low-growing vegetation. The energy relations of forest-canopy insects have attracted little attention, partly due to their great species diversity, but also because of the sampling problems associated with a relatively inaccessible habitat. Reichle & Crossley's (1967) work, using radioisotopes, has pioneered the study of energy flow in the canopy, but there remain opportunities for more contributions to an aspect of ecological energetics which has direct relevance to studies of forest primary production and decomposition (e.g. Ovington 1962). The present study was designed to provide energy budgets for a group of canopy defoliators in Monks Wood National Nature Reserve, Huntingdon, during 1965 and 1966. In the understorey of a temperate deciduous woodland sampling problems are less severe than in the high canopy. In the limited time available for this study it was therefore felt best to concentrate on this stratum, which in Monks Wood consists mainly of hazel (Corylus avellana L.). Traditionally, British oakwoods have been managed for coppice-with-standards; the hazel is felled in rotation, young stems sprouting densely from the old stools. During rotations of up to 12 years these stems rarely exceed 4 m in height and can be bent over for sampling purposes.