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Abstract 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 <.001) and diversity (P <.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 <.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. Highlights • Native vegetation recovery following E.camaldulensis removal is following a positive recovery trajectory. • Reinvasion of cleared sites by woody invasive alien plants has the potential to slow down the recovery process. • The removal of reinvading woody invasive alien plants is required to ensure ecological restoration success. [ABSTRACT FROM AUTHOR]

South Africa has a major problem with invasive plant species. Many species have long residence times, are well established, and have large invasive ranges, whereas others are still in the early stages of invasion. Predicting the full extent of invasions for species that have only recently started spreading is important for guiding management strategies. Ailanthus altissima is a widespread invasive species in many parts of the world. Although it has had a long residence time in South Africa, it is yet to replicate the extent of invasiveness and major impacts reported for the species in other parts of its adventive range. We mapped the countries in which A . altissima has been reported and evaluated the invasion status of the species in each (i.e. the position of the species on the introduction-naturalization-invasion continuum as conceptualized by Richardson and Pyšek, 2012). We then mapped the current distribution in more detail for South Africa. The species is known to be present in at least 51 countries and is invasive in 23 countries. Ailanthus altissima is present in all South African provinces except Limpopo and is most common and abundant in the Western Cape, Gauteng, Eastern Cape, and the Free State. We applied species distribution modelling using global distribution data to determine parts of the world, and in particular regions within South Africa, that are climatically suitable for the species. Large parts of Africa are potentially invasible by this species. Seven regions in South Africa were identified as high-risk areas for invasion by A . altissima . The species is already far too widespread in South Africa for eradication at the national scale to be feasible. A national strategy for managing the species should focus on: 1) early detection and rapid response in areas identified as climatically suitable and where the species is not already present; and 2) local and regional-scale initiatives based on objective prioritization in terms of feasibility of management success and asset protection. [ABSTRACT FROM AUTHOR]

This study investigated the autogenic recovery potential of native vegetation after clearing of dense stands of invasive alien trees in two critically endangered vegetation types in South Africa's Cape Floristic Region: Cape Flats Lowland Fynbos and Swartland Alluvium Fynbos. Sampling was done in areas previously occupied by the invasive tree Acacia saligna and plantations of Pinus radiata and in a fynbos reference site. Treatments varied in terms of the length of invasion and management histories. Plots previously under pines recovered well in terms of indigenous perennial species richness, but indigenous species cover decreased with increasing number of planting rotations. Areas cleared of acacia recovered poorly in terms of indigenous species cover (after one cycle of invasion), and indigenous species richness exhibited a declining trend with increasing cycles of invasion. Proteoid overstorey was lost in all previously invaded/planted plots and this element will need to be re-introduced to areas after one cycle of invasion regardless of the invasive species. Acacias changed some abiotic variables after two cycles of invasion. Follow-up clearing generally promoted better vegetation recovery in terms of overall species richness and structure but care should be taken not to damage indigenous ericoid shrubs. Overall, acacia invasion caused a greater change in biodiversity and vegetation structure than pine plantations. [ABSTRACT FROM AUTHOR]

Many invasive alien plants alter soil-nutrient regimes of invaded ecosystems, affecting management outcomes. We assessed the effects of Eucalyptus camaldulensis invasions on physical and chemical properties of riparian soils in the Western Cape Province, South Africa. Samples were collected from topsoil beneath the canopy of uninvaded and a gradient of invaded sites, namely, light, moderate and heavy over four seasons. We quantified soil moisture, temperature, litter depth and thickness, primary textural components, concentrations of soil macro (C, N, P and K) and micro (Mn, Zn, Cu and Fe) nutrients, and pH. Available N (NO3−-N and NH4+-N) and P, as well as exchangeable Ca and Mg were also assessed. Soil pH levels were significantly lower in invaded than in uninvaded sites in all seasons. Soil moisture decreased consistently with invasion intensity. Concentrations of macro, micro and available nutrients did not vary significantly along the invasion gradient ( p > 0.05), but exchangeable cation content was significantly higher in uninvaded than in invaded sites, especially in winter and spring. Sites invaded by E. camaldulensis had higher litter build-up than non-invaded sites, but this appears to have little effect on soil-nutrient regimes. It appears that restoration following removal of invasive stands of E. camaldulensis will not require major interventions to return soil to pre-invasion conditions. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]