Inducing whole-assemblage change by experimental manipulation of habitat structure

Summary

• 1
  Habitat 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.
• 2
  Fallen 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).
• 3
  We 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.
• 4
  Three 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.
• 5
  Fallen timber management needs to be considered in a landscape and temporal context for improving conservation of avian biodiversity.