The impact of canopy development on arthropod faunas in recently established Eucalyptus globulus plantations in Western Australia

Monthly samples of arthropods collected from foliage of newly planted bluegums (Eucalyptus globulus) during a period of 14 months revealed a diverse and abundant (35 000 individuals) fauna. Most species, however, were uncommon. Total arthropod biomass (relative to plant size) declined progressively, with minor peaks in late autumn and in the second spring. Sapsuckers dominated total biomass, with their biomass peaking in late autumn, nearly one year after planting. Chewers were the next dominant trophic level, but this was greatly biased by sporadic occurrence of large caterpillars. Predators and parasitoids each contributed <5% of total biomass. A space-for-time study of bluegums aged 6, 18 and 30 months yielded 34 000 arthropods. Total biomass increased rapidly up to 16 months and then stabilized. The proportion of sapsucker biomass halved between 18 and 30 months, while the proportion of chewer biomass increased fourfold. The greater proportion of older leaves on larger plants may have provided more suitable habitat for predators, but was less suited to sapsuckers. Observations of 11 types of chewers were collated using a conceptual framework summarizing mechanisms potentially affecting distributions of these insects in bluegum plantations in Western Australia. All four chewer types originating from agricultural habitat and reported as damaging plantations have soil-dwelling stages. Four of the five, damaging chewer types originating from remnant native vegetation have feeding or oviposition preferences which are influenced by canopy development. (C) 1999 Published by Elsevier Science B.V. All rights reserved.