Medium-term vegetation recovery after removal of invasive Eucalyptus camaldulensis stands along a South African river
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Effective ecological restoration requires detailed monitoring to determine the success achieved through different interventions in achieving objectives. In 2017, we resurveyed riparian sites along the Berg River in the Western Cape, South Africa, that have been cleared of invasive stands of Eucalyptus camaldulensis in 2010 using two clearing methods (fell-and-stackburn and fell-and-remove) and two restoration approaches: passive (where vegetation was allowed to recover without intervention) and active (assisted recovery). A significant increase in vegetation cover (P b .001) and diversity (P b .05) of native riparian species was recorded in passive restoration plots, but an increase in the cover of woody invasive alien plants was also observed. Only four of the nine native species that were planted to fast-track restoration were still present in the active restoration plots, but the abundance of these native species was significantly (P b .001) lower in 2017 than in 2011. We conclude that native vegetation recovery following E.camaldulensis removal seven years ago is following a positive recovery trajectory in both passive and active restoration sites, as shown by the increased occurrence of native trees and shrubs, e.g. Maytenus oleoides, Melianthus major and Searsia angustifolia which were not present before clearing. However, the reinvasion of cleared sites by woody invasive alien plants has the potential to slow down and potentially halt the recovery process. Further management interventions, e.g. removal of reinvading woody invasive alien plants, are required, emphasizing the sustained engagement to ensure restoration in these ecosystems.