Inducing whole-assemblage change by experimental manipulation of habitat structure

Authors

  • RALPH MAC NALLY,

    1. Australian Centre for Biodiversity: Analysis, Policy and Management, School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
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  • GREG HORROCKS

    1. Australian Centre for Biodiversity: Analysis, Policy and Management, School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
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R. Mac Nally, Australian Centre for Biodiversity: Analysis, Policy and Management, School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia. Tel.: +61 3 9905 5642. Fax: +61 3 9905 5613. E-mail: Ralph.MacNally@sci.monash.edu.au

Summary

  • 1Habitat structure long has been identified as a primary factor influencing local assemblage composition. Most evidence has been in the form of correlations of species occurrence and assemblage composition over a range of habitats, with experimental verification of relationships being relatively uncommon because of the difficulties of enacting precise manipulations of habitat structure.
  • 2Fallen timber (also known as coarse or large woody debris) is one of the few habitat-structural elements in forests and woodlands that can be manipulated with relatively high precision. We report on manipulations of wood-loads on 30 experimental 1-ha plots in floodplain forests of northern Victoria, Australia, over 4 years (one pre- and three post-manipulation).
  • 3We show that very high wood-loads (80 Mg ha−1) and intermediate wood-loads derived from tree crowns (40 Mg ha−1) increase species richness (all species and ground-foraging species) and numbers of birds (all species and ground-foraging species) relative to the control plots.
  • 4Three bird species consistently increased most following manipulations: white-plumed honeyeater Lichenostomus penicillatus (Gould 1837) (fam. Meliphagidae), brown treecreeper Climacteris picumnus (Temm. & Laug. 1824) (fam. Climacteridae) and yellow rosella Platycercus elegans flaveolus (Gould 1837) (fam. Psittacidae). The honeyeater is not considered as a ground or fallen timber dependent species, while the treecreeper and rosella both are regarded as being dependent on ground-layer structure.
  • 5Fallen timber management needs to be considered in a landscape and temporal context for improving conservation of avian biodiversity.

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