Recovery of benthic macroinvertebrate and adult dragonfly assemblages in response to large scale removal of riparian invasive alien trees |
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Authors: | Rembu N Magoba Michael J Samways |
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Institution: | (1) Department of Conservation Ecology and Entomology, and Centre for Invasion Biology, University of Stellenbosch, P/Bag X1, Matieland, 7602, South Africa; |
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Abstract: | Invasive alien organisms can impact adversely on indigenous biodiversity, while riparian invasive alien trees (IATs), through
shading of the habitat, can be a key threat to stream invertebrates. We ask here whether stream fauna can recover when the
key threat of riparian IATs is removed. Specifically, we address whether IAT invasion, and subsequent IAT removal, changes
benthic macroinvertebrate and adult dragonfly assemblages, for the worse or for the better respectively. Natural riparian
zones were controls. There were statistically significant differences between stream reaches with natural, IAT-infested and
IAT-cleared riparian vegetation types, based on several metrics: immature macroinvertebrate taxon richness, average score
per macroinvertebrate taxon (ASPT), a macroinvertebrate subset (Ephemeroptera, Plecoptera, Trichoptera and Odonata larvae;
EPTO), and adult dragonfly species richness. Reaches with natural vegetation, or cleared of IATs, supported greater relative
diversity of macroinvertebrates than reaches shaded by dense IATs. Greatest macroinvertebrate ASPT and EPTO were in reaches
bordered by natural vegetation and those bordered by vegetation cleared of IATs, and the lowest where the riparian corridor
was IATs. Highest number of adult dragonflies species was along streams cleared of dense IATs. Overall, results showed that
removal of a highly invasive, dense canopy of alien trees enables recovery of aquatic biodiversity. As benthic macroinvertebrate
scores and adult dragonfly species richness are correlated and additive, their combined use is recommended for river condition
assessments. |
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Keywords: | |
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