Littoral Macroinvertebrates in Relation to Native and Exotic Riparian Vegetation in Streams of Central Victoria, Australia

摘要

Exotic willows (Salix spp.) are widespread riparian tree species of rivers in temperate Australia and New Zealand. Willow removal is an integral part in riparian management of rivers in temperate Australia. Reeds (Phagmites australis) and shrubs (Leptospermum spp. and Callistemon spp.) are common vegetation in the riparian zone of Victorian streams and considered suitable for planting along channels in revegetation programmes following willow removal. Little is known about the novel habitats created by willows and the impact on aquatic biota of vegetation successional process following willow management programmes. Macroinvertebrate fauna in willow, Phragmites australis, Leptospermum/ Callistemon and bare bank habitats were examined in three central Victorian streams in Australia to understand the effect of such littoral habitats on macroinvertebrates taxa richness, abundance and community composition. Data were analysed using a two way ANOVA with habitat and season as main effects. Habitats had a significant effect (p<0.05) on macroinvertebrate taxa richness. Willow and Phragmites habitats generally contained more taxa and total number of individuals than Leptospermum/ Callistemon or bare bank habitats though the absolute rank order of habitats differed among seasons. In Phragmites habitats species richness was higher during winter and spring. In willow habitats it was higher during spring and autumn and in Leptospermum/ Callistemon habitats during summer. Multivariate analysis showed that community composition within the habitats was significantly different, with willow and Phragmites separating from Leptospermum/ Callistemon and bare bank habitats in seasons with high flow. It appears that a vegetation transition from willows to bare banks or shrubs alone would be potentially more disruptive to macroinvertebrate communities than a transition from willows to a combination of littoral reeds and native riparian vegetation. This result suggests that exploration of techniques to guide a transition from willow to native littoral and riparian vegetation without a disruptive clearing phase is therefore desirable.