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Snapshot of interim output from software used for rendering three-dimensional images of Eucalyptus obliqua tree structure based on real-life measurements. |
Image: Yoav Bar-Ness |
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Project summary:
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 Tasmania. Despite their critical role in the economy and ecology of Tasmania, few studies have addressed the canopy arthropod biodiversity of these trees.
The two age classes of trees studied were quantifiably different in crown structure. 100 year old trees had young mature crowns of original branches. Older 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.
Old trees showed a more diverse community structure and the evidence suggested a richer fauna in these trees. The age classes showed differences in composition that were often masked by environmental effects. The structural descriptors were tested against the arthropod biodiversity variables to explore the influence of crown structure on canopy arthropod communities. In the context of the study trees, several rank correlations were identified, including the findings that: old trees with a higher proportion of their total wood volume in the trunk had a more diverse total arthropod fauna. Trees with less crown depth had a richer Diptera fauna. Trees with a narrower range of dead branch starting diameters had a more diverse sticky trap catch. Trees with a wider range of live branch starting diameters had a richer hangtrap catch. Old trees with greater mean upwards arc had a richer hangtrap catch. Trees with a lower mean branch height as % of total height had a richer hangtrap catch. No other study is known to have investigated the influence of crown structure on canopy arthropod biodiversity in a forest tree. Download a pdf (1.2 mb) of a PowerPoint presentation given at Forestry Tasmania in March 2005
Methodology: Eight 100-year-old and eight old-growth (300-500 year-old) trees were studied in pairs. 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 intercept traps, and funnel crawl traps were placed in the crown to sample mobile arthropods.
Datasets: None available.
Publications: Bar-Ness, Y. (2005). Crown structure and the canopy arthropod biodiversity of 100 year old and old-growth Tasmanian Eucalyptus obliqua. Masters thesis, University of Tasmania, Hobart.
Bar-Ness, Y.D., Kirkpatrick, J.B. & McQuillan, P.B. (2006). Age and distance effects on the canopy arthropod composition of old-growth and 100-year-old Eucalyptus obliqua trees. Forest Ecology and Management 226: 290-298.
Wardlaw, T., Grove, S., Hopkins, A., Yee, M., Harrison K. & Mohammed, C. (2009). The uniqueness of habitats in old eucalypts: contrasting wood-decay fungi and saproxylic beetles of young and old eucalypts. Tasforests 18: 17-32.
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