Using tree hollow data to define large tree size for use in habitat assessment |
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Authors: | S K Travers J Dorrough I Oliver M Somerville C J Watson M J McNellie |
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Institution: | 1. Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, UNSW Sydney, Australia;2. Department of Planning and the Environment, Office of Environment and Heritage New South Wales, Merimbula, Australia;3. Department of Planning and the Environment, Office of Environment and Heritage New South Wales, Gosford, Australia;4. Department of Planning and the Environment, Office of Environment and Heritage New South Wales, University of New England, Armidale, Australia;5. Department of Planning and the Environment, Office of Environment and Heritage New South Wales, Sydney South, Australia;6. Department of Planning and the Environment, Office of Environment and Heritage New South Wales, Wagga Wagga, Australia |
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Abstract: | Habitat assessments often require observers to estimate tree hollows in situ, which can be costly, destructive and prone to bias. An alternative is to count the number of trees above a specific size. The size at which a tree develops hollows differs substantially among tree species. To assist with setting standards for habitat assessment we defined a large tree as the size at which a species has a 50% probability of supporting a 2-cm diameter hollow. We estimated this size for 68 species using a meta-analysis based on 18 data sources. We found that large tree size ranged from 21 to 106 cm diameter at breast height (DBH). Each species was attributed to vegetation types (formations and classes) to explore variation in large tree sizes. Despite considerable variation within vegetation classes and formations, our results suggest that a large tree size of approximately 50 cm DBH may be appropriate for most vegetation types, with lower estimates in semi-arid vegetation (~30 cm) and higher estimates in wet sclerophyll forests (~80 cm). Our estimates provide empirical support for defining large trees at species vegetation class and formation levels within New South Wales, and highlights the need for more empirical data. |
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Keywords: | habitat quality tree cavity habitat condition vegetation condition biodiversity metric biodiversity indicator biodiversity benchmarks |
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