The crown structure and canopy arthropods of Eucalyptus obliqua were studied at the Warra Long Term Ecological Research Site in the wet sclerophyll forests of Southern udTasmania. Eight 100 year old and eight old-growth (between 300-500 years old) trees were studied in pairs. Despite their critical role in the economy and ecology of Tasmania, few studies have addressed the canopy arthropod biodiversity of these trees. The crown structure was mapped by recording a vector in spherical space for every branch. 3- dimensional computer models were generated to aid in illustrating the tree maps. Sticky traps, flight udintercept traps, and funnel crawl traps were placed in the crown to sample mobile arthropods. The age classes were quantifiably different in crown structure. 100 year old trees had young mature crowns of original branches. Old trees had either senescent original crowns or resprouted epicormic secondary crowns. Old trees expressed a greater variability in crown structure, and were more complex as measured by the amount of information required to display the computer image. Structural attributes such as hollows, dead tops, dead flanks, trunk fissures, burls, vascular epiphytes, snapped trunks, and litter collections were all present more often in the old trees than the 100 year old trees.
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