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The South African Department of Forestry, Fisheries, and the Environment (DFFE) is thanked for funding. To support and scale up global restoration efforts, the United Nations (UN) has proclaimed 2021-2030 the "UN Decade on Ecosystem Restoration". The Decade offers significant opportunities for and challenges to restoration, in particular for Africa, a continent that has a large need and potential for restoration. We thus argue that the Decade must be a success in and for Africa, and for this to happen, opportunities and challenges to achieving its goals must be promptly identified, and considered in the planning and implementation of restoration. Here, we outline six key areas that should be considered at a strategic level by African countries during the Decade. These are: (1) ensuring effective oversight and governance relevant to Africa; (2) translating the goals to meet the African context; (3) making the case for restoration amid multiple development demands; (4) growing an African restoration community of practice based on regional need; (5) collaborating to improve restoration outcomes; and (6) establishing an Africa-relevant evidence base for restoration. We believe that these six key areas - even though they are not all novel - are currently not addressed at a level that matches the scale of the problem on the continent. Although the specific actions to be taken under each key area are dependent on the restoration context, integrating these key areas in the planning and implementation of restoration efforts will likely lead to improved restoration outcomes during the Decade. Postprint

Invasive alien nitrogen-fixing species, such as Australian acacias, often leave a legacy of elevated available soil nitrogen after their removal. This legacy effect can facilitate secondary invasion by other alien species, thereby preventing natural restoration of areas being managed. To restore viable native plant communities in ecosystems where secondary invasion is a barrier to restoration, it is important to understand the soil legacy effects of invasions. Using Acacia saligna (Labill.) H. L. Wendl. (Fabaceae) invasions in the South African fynbos as case study, we determined (1) the extent to which levels of available soil nitrogen influence the germination and growth of secondary invaders; and (2) how this differs between secondary invader species. We chose five of the most common species that have been identified as secondary invaders after clearing invasive A. saligna in the Cape Flats Sand Fynbos: (i) Avena fatua (L.) (Poaceae), (ii) Briza maxima (L.) (Poaceae), (iii) Bromus diandrus (Roth.) (Poaceae), (iv) Hypochaeris radicata (L.) (Asteraceae), and (v) Raphanus raphanistrum (L.) (Brassicaceae). Using proportional fertigation, we created soil nitrate levels similar to those found in non-invaded areas (1mg/kg), and the lowest (3 mg/kg), median (7.5 mg/kg) and highest (12 mg/kg) levels typically found in areas previously invaded by A. saligna up to ten years after clearing. For each soil nitrate level, we germinated secondary invader seeds (five seeds per petri dish) in an incubator (five species × four soil nitrate levels × five replicates = 100 petri dishes). Furthermore, for each soil nitrate level, we grew secondary invaders (one plant per pot) in a greenhouse tunnel for five months (five species × four soil nitrate levels × five replicates = 100 pots). There was no significant relationship between germination success and soil nitrate level for any species. However, root and shoot dry mass were significantly positively correlated to soil nitrate level for all species. The relationship was nonetheless only linear for Bromus diandrus, Hypochaeris radicata, and Raphanus raphanistrum. These results indicate that the legacy of elevated available soil nitrogen does not have an effect on the germination of secondary invaders, but favours their growth. Therefore, secondary invasion can be managed through a reduction in soil nitrogen levels. However, secondary invader growth does not decrease at the same rate for all species in response to a decrease in available soil nitrogen. Thus, the use of soil nitrogen reduction as a tool for the management of secondary invasions should take into account the species being managed. However, given that multiple secondary invader species often dominate a restoration site, restoration efforts should reduce soil nitrogen to non-invaded levels to account for the different response rates to available soil nitrogen, and simply management efforts.

It is often assumed that clearing invasive alien species will lead to the dissipation of their negative impacts and recovery of native plant diversity. 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 invasive 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. Overall, we set out to (1) identify species that are secondary invaders; (2) determine whether secondary invader richness and cover differ between where there were high and low severity fires and no fires, and how these differences change with years after clearing; and (3) determine whether secondary invader richness and cover differ in and between lowland and mountain fynbos, and how these differences change with years after clearing. We identified 32 secondary invader species. Mean secondary invader richness was lower where there were high severity fires (2.75) compared to where there were low severity fires (3.28) and no fires (3.24). Mean secondary invader proportion cover was lower where there were no fires (0.14) compared to where there were high severity fires (0.19) and low severity fires (0.2). Three years after clearing, secondary invader richness and cover had not changed or was now higher than in the first year, while secondary invader richness was similar between lowland and mountain fynbos. Secondary invader cover was similar between lowland and mountain fynbos up to two years after clearing but was 58% lower in lowland fynbos in the third year. Fire application after clearing invasive acacias can have positive (i.e. reduction of Acacia soil seed banks by triggering mass germination) and negative (i.e. favors the dominance of secondary invaders) effects. As a result, slash should be spread throughout the restoration site instead of being stacked and then burnt to reduce Acacia soil seed banks. To avoid the establishment of a second generation of invasive acacias, the seedlings that germinate can be controlled through manual weeding, mowing and herbicide application. Due to the persistence and abundance of secondary invaders up to three years after clearing at levels similar to or higher than in the first year, we conclude that practicing restoration ecologists must manage these species to ensure successful restoration of native plant diversity.

This chapter reviews the increasing importance of Mediterranean pines as invasive non-native species outside the natural range of the genus, especially in temperate parts of the Southern Hemisphere where several species are important weeds. It first discusses human-mediated changes to the ranges of Mediterranean pines and their colonization and persistence ability within and immediately adjoining their natural ranges. Next, it reviews the history of plantings and emergence of invasions of these pines in the Southern Hemisphere. Aspects of the ecology of the most widespread invaders (P. halepensis and P. pinaster) are discussed by considering the factors that influence invasive success. The impacts of the invasive pines are discussed, and management approaches and challenges are reviewed.

This Commentary is a response to a Commentary published in the May/June 2020 issue: Nattrass N. Why are black South African students less likely to consider studying biological sciences? S Afr J Sci. 2020;116(5/6), Art. #7864, 2 pages. https://doi.org/10.17159/sajs.2020/7864 Responses to the Commentary in the May/June 2020 issue have been published collectively in a special issue of Volume 116.

Invasive alien plant species can be a major cause of ecosystem degradation in South Africa, and ecosystem recovery may require restoration interventions beyond controlling the target alien species. Active restoration interventions are usually required if legacy effects result from the invasion. Legacy effects may induce regime shifts when thresholds to autogenic recovery are breached. In such cases, active restoration interventions will be required to manipulate the ecosystem along a trajectory to recovery. In some cases, alien control measures may be sufficient to restore a structurally and functionally representative ecosystem, provided that implementation occurs early in the invasion process and that the control methods do not hamper spontaneous regeneration. It is important that key stakeholders discuss and set realistic restoration goals at the project planning stage. Studies on the costs and benefits of ecological restoration indicate that when important services are improved, benefits outweigh the costs of alien clearing (assuming spontaneous regeneration of the native ecosystem). The costs of moderate, active restoration interventions are economically viable, whereas the costs of fully restoring ecosystem structure, functioning and composition in highly degraded ecosystems are rarely deemed economically justifiable. Valuations of specific biodiversity components, such as threatened ecosystems and species, remain problematic to assess, and these components could be under-valued in such studies. South African researchers have made significant contributions to the theory and practice of restoration ecology globally and have produced local guidelines for ecological restoration. However, there has been limited uptake in implementing active restoration projects at larger scales. This apparent knowing-doing gap may have three causes: firstly, insufficient co-production by all stakeholders in planning restoration projects, including prioritisation and goal setting; secondly, shifting beyond clearing invasive alien species to restoring ecosystems; and thirdly, insufficient resources to implement active restoration projects at the necessary scale. To achieve Convention on Biological Diversity and the UN Sustainable Development Goals, interventions must shift from controlling invasive alien species alone to restoring native ecosystem structure and functioning.

Invasive Australian acacias can alter soil chemistry and microbial communities in areas they invade. After clearing invasive acacias, these changes can persist, and previously invaded areas can become dominated by nitrophilic weedy species. Restoration of viable native plant communities in cleared sites often fails due to a lack of native species re-establishment. Therefore, to improve restoration outcomes, it is important to understand the effects of soil chemical and biotic legacies, and of nitrophilic weedy species, on native species re-establishment. To investigate the effect of soil chemical legacies, we germinated and grew Protea repens seedlings (a native proteoid shrub) as an indicator species in soil taken from areas cleared of Acacia saligna in lowland fynbos, as well as from non-invaded areas under controlled conditions. To investigate the effect of soil biotic legacies, we sterilized half the soil from each cleared or non-invaded area. We grew Ehrharta calycina (a native nitrophilic weedy grass species) in half of each treatment and measured the effect of treatments on P. repens germination and growth. Germination percentage, root and shoot dry mass of P. repens did not significantly differ between altered and native soil chemistry. The germination percentage of P. repens was significantly greater (93%) in the presence of soil microbial communities than in their absence. The presence of E. calycina significantly increased (29%) the root-to-shoot ratio of P. repens than their absence. Since the legacy of altered soil chemistry did not have a direct negative effect on P. repens germination and growth; we conclude that restoration efforts do not always have to manage altered soil chemistry after clearing invasive A. saligna.

Impacts of invasive alien N₂‐fixing woody species and how they can persist as soil legacy effects after invasive species control are well appreciated, but how soil legacy effects can present barriers to restoration is poorly understood. Finding better ways to deal with these barriers to restoration is essential to improving restoration outcomes. In this study, we review 440 studies to identify barriers to restoration and potential management actions for the barriers to restoration, and provide practical application examples of the management actions. Our findings suggest that altered soil microbial communities, depleted native soil seed banks, elevated N status, secondary invasion and weedy native species dominance, and reinvasion are potential barriers to restoration. Furthermore, carbon addition, litter removal, soil microbial treatments, establishing species adapted to low N levels, prescribed burning, classical biological control, grazing, mowing, herbicide or graminicide application, manual weeding, soil N management, soil solarization, weed mats, native species reintroduction, and nurse plants are potential management actions for these barriers to restoration. However, there is little evidence suggesting that several of these barriers to restoration hinder improved restoration outcomes and this could be due to little research on them. More research is needed to assess their relative importance in hindering improved restoration outcomes. Management actions are rarely applied in combination, despite that they often address distinct barriers to restoration. Management actions should be combined into an integrated management effort to improve restoration outcomes.

To reduce the negative impacts of invasive plants, management interventions such as control or eradication are usually necessary. It is often assumed that the impacts of invasive plants will diminish immediately after such interventions. However, in some cases the invader can have legacy effects in the soil that might persist for long periods, preventing the natural restoration of the areas managed. Therefore, to achieve the re-establishment of a functional native ecosystem it is important to understand for how long such legacies can persist in the soil. This paper explores this issue, using Acacia saligna in South Africa as case study. We collected soil samples in invaded, non-invaded and previously invaded sites (representing 2, 6 and 10 years after clearing) and analysed the levels of pH, carbon, nitrogen, available phosphorus, ammonium, nitrate and electrical conductivity. We also analysed enzyme activities (β-1,4-glucosidase, urease and acid phosphatase). Acacia saligna invasion alters overall soil characteristics but specifically raises pH by 0.6–1.8. Moreover, soil characteristics (e.g. pH) are not restored to natural conditions after control (soil legacy effects persist up to 10 years after clearing). Furthermore, A. saligna control elevates soil NO3− levels and these can remain higher than in invaded (1.55–6.67 mg kg−1) and non-invaded (2.16–4.35 mg kg−1) sites up to 10 years after clearing. Elevated NO3− often facilitates secondary invasion and/or weedy native species dominance which may hinder the restoration of functional native ecosystems. Therefore, strategies to manage areas previously invaded by A. saligna should take into account the removal of litter from the target invader, secondary invaders and weedy native species.

Cape Vultures Gyps coprotheres have black patches on their upperwing greater secondary coverts and black spots on their underwing greater secondary coverts. These have been physically observed to differ with individuals. This study examined the effects of age in years and sex on the size of the patches and spots using computer feather image analysis of birds with known ages in order account for differences that pure observation alone could possibly miss. Despite statistical analysis of computer enhanced imagery of micro detail the chosen plumage pattern failed to yield a reliable way to age and sex Cape Vultures. Annual moult is not expected in this species making the correlation of moult to age a muddle as it is also influenced by external factors such as captivity, stress, food, endocrine (sexual changes), and latitude. This study was limited by the lack of understanding of the exact moulting sequence of upperwing and underwing greater secondary coverts of the Cape Vulture, and as a direct result of this, analysis of the chosen plumage was maintained instead of the feather that is moulted in that particular year.,Hlengisizwe Ncube VulPro NPC, Walter Neser, Kerri Wolter and Obert Phiri