Does wood type influence the colonisation of this habitat by macroinvertebrates in large lowland rivers?

Abstract

Submerged woody habitat provides the major structure around which ecological processes operate in many lowland rivers. Colonisation by macroinvertebrates was measured in a south-eastern Australian river over a 32-day period in an experiment testing the hypothesis that wood type influences the invertebrate assemblage structure. The wood types were green wood, dry wood, and dry but previously waterlogged wood. All wood used was river red gum (Eucalyptus camaldulensis). Macroinvertebrates colonised previously waterlogged wood more rapidly than green or dry wood. The assemblage structure varied significantly over the sampling period, with copepods and cladocerans numerically dominating the assemblage during the first few days after the introduction of the wood. The assemblage became more diverse through time and was numerically dominated by dipterans, ephemeropterans and trichopterans. The results indicate that there was little difference in the time taken for macroinvertebrate colonisation after wood introduction when using either green or dry wood. This has implications for large-scale restoration projects, where green wood is likely to be a more readily available option for reintroduction than dry wood.