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Does the quality and size of native vegetation remnants within blue-gum plantations influence ground-dwelling invertebrate assemblages?

invertebrate assemblages

Chela Powell and her supervisor, Nick Collett, complete fieldwork within a remnant adjacent to a blue-gum plantation in the green triangle region of SA/ VIC.

­The influence that the size and quality of a habitat patch have on ground-dwelling invertebrate assemblages is one of the research questions being pursued by Chela Powell, a PhD student at the University of Melbourne. Chela has a number of remnant native vegetation sites within the blue-gum plantation landscapes in the Green Triangle region of South Australia and Victoria. These remnants were classified into four different vegetation qualities defined using the Land for Wildlife method and two different size classes - small (1-5 ha) and large (>5 ha).

Chela sampled ground-dwelling invertebrates in continuous and remnant woodland vegetation, during each season from June 2007 to June 2008, using pitfall traps. The captured invertebrates were identified to a coarse level and then the three most abundant beetle families (Carabidae, Staphylinidae and Tenebrionidae) were identified to genus or species level.

Chela found some interesting, but unexpected, results. Overall, mean invertebrate and Coleoptera (beetle) abundance generally increased with decreasing remnant vegetation quality while higher quality remnant sites were generally characterised by greater diversity. However, when different taxonomic groups were compared on a finer scale of classification (family, genus or species), different groups showed contrasting responses to vegetation quality. For example, Staphylinidae and Tenebrionidae beetles bucked the general trend and displayed higher diversity in lower quality remnant sites. Remnant size was a significant determinant of the diversity of some, but not all, groups; some groups of invertebrates were better represented in large remnants, while others displayed higher diversity in smaller remnants.  

The implications of these results for the management of remnant invertebrate biodiversity within the plantation landscape is that a range of remnants of differing qualities and size should be maintained in the landscape in order to conserve the broadest diversity of invertebrates. The Land for Wildlife method of vegetation assessment is a quick and relatively user-friendly method that has shown to be indirectly related to vegetation structural attributes important for ground-dwelling invertebrates.

Biobuzz issue nine, August 2009