Browsing by Author "Esler, K. J."

Now showing 1 - 7 of 7
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    A decision-making framework for restoring riparian zones degraded by invasive alien plants in South Africa
    (Academy of Science of South Africa -ASSAf, 2005-11) Holmes, P. M.; Richardson, David M.; Esler, K. J.; Witkowski, E. T. F.; Fourie, S.
    Riparian habitats in many parts of South Africa are severely degraded by invasive alien plants, especially trees. These invasions reduce water yields from catchments and affect riverine functioning and biodiversity. Initiatives are under way countrywide to clear alien plants from watercourses and surrounding catchments. Current understanding of key processes that regulate riparian functioning and define options for restoration is rudimentary. We review the impacts of riparian invasions and identify factors limiting the recovery of natural vegetation following alien clearance. We propose a framework of strategic interventions for optimizing restoration success. The framework identifies abiotic and biotic barriers to restoration at the scales of catchments and local reaches. In highly transformed catchments, interventions at the reach scale may fail if important barriers at the catchment scale are not addressed. The extent to which propagule supply and microsite conditions inhibit vegetation recovery is unknown. We also know little of the relative importance of dispersing vegetative propagules, dispersing seeds and soil-stored seed banks in vegetation dynamics, particularly after severe disturbances such as dense invasion by alien plants. The importance of geomorphological and hydrological factors in mediating recovery of riparian vegetation has not been adequately explored for all climatic areas in South Africa. More research is needed to determine the influence of different alien species and clearing treatments on the recovery of riparian vegetation. The literature strongly suggests that in highly alien-transformed catchments, the re-introduction of riparian species is required to promote recovery and suppress re-invasion. However, such interventions are unlikely to be widely implemented unless the cost:benefit ratios are favourable.
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    Diversity and species turnover on an altitudinal gradient in Western Cape, South Africa : baseline data for monitoring range shifts in response to climate change
    (AOSIS, 2008) Agenbag, L.; Esler, K. J.; Midgley, G. F.; Boucher, C.
    A temperature and moisture gradient on the equator-facing slope of Jonaskop on the Riviersonderend Mountain, Western Cape has been selected as an important gradient for monitoring the effects of climate change on fynbos and the Fynbos-Succulent Karoo ecotone. This study provides a description of plant diversity patterns, growth form composition and species turnover across the gradient and the results of four years of climate monitoring at selected points along the altitudinal gradient. The aim of this study is to provide data for a focused monitoring strategy for the early detection of climate change-related shifts in species' ranges, as well as gaining a better understanding of the role of climate variability in shaping species growth responses, their distributions, and other ecosystem processes.
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    Effects of alien plant management, fire and soil chemistry on selected soil microbial populations in the Table Mountain National Park, South Africa
    (NISC Pty Ltd., 2005-06) Cilliers, C. D.; Botha, A.; Esler, K. J.; Boucher, C.
    This pilot study examined changes in soil chemistry and microbial population sizes following the extensive wildfires in 2000 on the Cape Peninsula. The effects of standing alien plants and stacks of mechanically-cleared alien plant material on selected post-fire microbial populations and their recovery were investigated. These were compared to burnt fynbos and the burnt cleared areas surrounding wildfire burnt stacks. Microbial population sizes and chemical changes were also monitored in unburnt fynbos and dense unburnt stands of invasive alien plants. Differences in soil chemistry and microbial population sizes occurred in the samples taken from the various post-fire environments while marked seasonal changes were also apparent. Microbial population sizes were linked to pre-fire vegetation characteristics, fire intensity, the management of alien plants, soil chemical changes and seasonal influences. High volumes of woody alien plant biomass impacted on post wildfire microbial population sizes during summer. During winter, however, microbial population sizes were primarily influenced by soil texture and nutrient composition. Copyright © NISC Pty Ltd.
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    Medium-term vegetation recovery after removal of invasive Eucalyptus camaldulensis stands along a South African river
    (Elsevier, 2018) Ruwanza, S.; Gaertner, M.; Esler, K. J.; Richardson, D. M.
    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.
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    North-south cooperation through BIOTA : an interdisciplinary monitoring programme in arid and semi-arid southern Africa
    (Academy of Science for South Africa, 2006) Krug, C. B.; Esler, K. J.; Hoffman, M. T.; Henschel, J.; Schmiedel, U.; Jurgens, N.
    CONNECTING DISCIPLINES IN A NORTH-South collaboration has many advantages: mutualisms evolve, synergies are created and spin-offs emerge. The BIOTA South (Biodiversity Monitoring Transect Analysis in southern Africa) programme, with its long-term vision to generate knowledge of biodiversity along a north-south transect in southern Africa, is providing opportunities for research, technology transfer and capacity building while focusing on potential solutions for critical challenges that face this environmentally vulnerable part of the subcontinent.
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    Priority questions for biodiversity conservation in the Mediterranean biome: Heterogeneous perspectives across continents and stakeholders
    (Wiley, 2019) Moreira, F.; Allsopp, N.; Esler, K. J.; Wardell-Johnson, G.; Ancillotto, L.; Arianoutsou, M.; Clary, J.; Brotons, L.; Clavero, M.; Dimitrakopoulos, P. G.; Fagoaga, R.; Fiedler, P.; Filipe, A. F.; Frankenberg, E.; Holmgren, M.; Marquet, P. A.; Martinez-Harms, M. J.; Martinoli, A.; Miller, B. P.; Olsvig-Whittaker, L.; Pliscoff, P.; Rundel, P.; Russo, D.; Slingsby, J. A.; Thompson, J.; Wardell-Johnson, A.; Beja, P.
    ENGLISH ABSTRACT: The identification of research questions with high relevance for biodiversity conservation is an important step towards designing more effective policies and management actions, and to better allocate funding among alternative conservation options. However, the identification of priority questions may be influenced by regional differences in biodiversity threats and social contexts, and to variations in the perceptions and interests of different stakeholders. Here we describe the results of a prioritization exercise involving six types of stakeholders from the Mediterranean biome, which includes several biodiversity hotspots spread across five regions of the planet (Europe, Africa, North and South America, and Australia). We found great heterogeneity across regions and stakeholder types in the priority topics identified and disagreement among the priorities of research scientists and other stakeholders. However, governance, climate change, and public participation issues were key topics in most regions. We conclude that the identification of research priorities should be targeted in a way that integrates the spectrum of stakeholder interests, potential funding sources and regional needs, and that further development of interdisciplinary studies is required. The key questions identified here provide a basis to identify priorities for research funding aligned with biodiversity conservation needs in this biome.
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    SAWISE and HERS-SA : raising the profile of women in science
    (Academy of Science for South Africa, 2006) Esler, K. J.; Shackleton, L.; Chinsamy-Turan, A.
    [No abstract available]