Secondary invasion after clearing invasive Acacia saligna in the South African fynbos

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Mlungele Nsikani

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It is often assumed that clearing invasive alien species will lead to the dissipation of their negative impacts and recovery of native biodiversity. However, this is often not the case because clearing of primary invasive alien species can lead to secondary invasion by non-target species. We investigated the effects of vegetation type and application of fire during management of biomass after clearing invasive acacias on secondary invasion in the South African fynbos. Furthermore, we determined how these effects change with years after clearing. We sampled vegetation in lowland and mountain fynbos cleared of Acacia saligna using the “fell, stack and burn” method. During burning of the stacked slash, the area at the centre of the stack experiences a high severity fire while the area at the edge experiences a low severity fire. After fire, burn scars remain in place of the stacked slash. We sampled in and outside of 80 burn scars over three years after clearing. We identified 32 secondary invader species. Secondary invader cover was lower where there were no fires compared to where there were high severity fires (27%) and low severity fires (30%). Three years after clearing, secondary invader richness and cover remained similar to or higher than in the first year, while secondary invader richness was similar between lowland and mountain fynbos. We conclude that practicing restoration ecologists have to manage these species to ensure successful restoration of native biodiversity.

Resource Type:
Audio/Video, Conference Presentation, SER2019

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Society for Ecological Restoration