The vegetation cover dynamics and potential drivers of habitat change over 30 years in the Free State National Botanical Garden, South Africa

Abstract

As a conservation strategy, the South African National Biodiversity Institute (SANBI) establishes biodiversity gardens in areas with unique vegetation types that are vulnerable to extinction. The study aimed to (1) determine the vegetation cover dynamics of the Free State National Botanical Garden (FSNBG) over a 30-year period (1987–2017), focusing on different vegetation classes; (2) evaluate the ecological integrity of the Critical Biodiversity Area 1 (CBA1) vegetation using species abundance and vegetation cover; and (3) quantify potential conservation threats that may be drivers of vegetation cover changes. The “moderate vegetation cover” and “dense vegetation cover” had increased by 25.1 ha and 8.6 ha respectively in the FSNBG. Woody vegetation cover expanded significantly over the past 30-year period, suggesting “bush” encroachment. Shannon–Wiener diversity indices showed high overall plant species diversity of CBA1 vegetation type (H = 3.5), with the vegetation cover remaining high (79.6 ± 15.9%), 50 plant species no longer existing, suggesting reduced taxonomic richness. Major conservation threats included the presence of 27 alien and invasive plant species interspersed within different vegetation patches and anthropogenic habitat fragmentation in the past 19 years (i.e. covering ~ 18% of the buffer zone). We conclude that increased vegetation cover is associated with bush encroachment and we recommend interventions to reduce the population density of woody plants and establish permanent vegetation monitoring plots.

The Potential of Foraging Chacma Baboons (Papio ursinus) to Disperse Seeds of Alien and Invasive Plant Species in the Amathole Forest in Hogsback in the Eastern Cape Province, South Africa

“…The NDVI value ranges between −1.0 and +1.0, and reflects the health of plants (greens). An NDVI value of 0.6 to 1 represents dense vegetation cover, 0.4 to 0.6 represents moderate vegetation cover, 0.2 to 0.4 represents sparse vegetation cover, 0.1 to 0.2 shows grass cover with bare space, and −1 to 0.1 represents no vegetation, i.e., water cover [88].…”

Success in restoring native plant communities on kimberlite mining dumps in the Afro‐alpine Drakensberg region of Lesotho

“…Two large priority surfaces targeted for rehabilitation at Letšeng Diamond Mine comprise the coarse and fine kimberlite tailings facilities. There is generally limited information and understanding of the establishment of vegetation in grasslands that have undergone severe disturbance (Vukeya et al., 2023 ). These shortcomings fail to achieve the desired rangeland use in the Lesotho Drakensberg.…”

Determining the critical recruitment needs for the declining population of Olea europaea subsp. africana (Mill.) P.S. Green in Free State, South Africa

“…Grasslands are threatened by fragmentation, which involves the splitting of natural habitats into smaller isolated patches primarily by human disturbances such as land clearing for human settlement (Bredenkamp et al, 2006 ; Carbutt & Kirkman, 2022 ; Matsika, 2008 ; Neke & du Plessis, 2004 ; Skowno et al, 2019 ; Vukeya et al, 2023 ), agricultural activities (Matsika, 2008 ; Nkuekam et al, 2018 ; Turpie et al, 2007 ), and mining activities (Brown & du Preez, 2014 ; Olivier, 2020 ). Several studies have reported that 40% of the grassland biome has been irrevocably modified while 60% of remaining grassland areas are threatened as they are losing an important aspect of their composition, structure, and function (Little et al, 2015 ; Neke & du Plessis, 2004 ; SANBI, 2013 ; Skowno et al, 2019 ), which may need urgent restoration for biodiversity conservation.…”

“…Several studies have reported that 40% of the grassland biome has been irrevocably modified while 60% of remaining grassland areas are threatened as they are losing an important aspect of their composition, structure, and function (Little et al, 2015 ; Neke & du Plessis, 2004 ; SANBI, 2013 ; Skowno et al, 2019 ), which may need urgent restoration for biodiversity conservation. In South Africa, the continuous habitat fragmentation is likely to increase biodiversity loss (Mullu, 2016 ), particularly for the critically endangered grassland biome species (Brown & du Preez, 2014 ; Matsika, 2008 ; Turpie et al, 2007 ; Vukeya et al, 2021 ); for example, this is observed in the southern Drakensberg Grassland (Turpie et al, 2007 ), and Bloemfontein Karroid Shrubland conserved in the Free State National Botanical Garden (Vukeya et al, 2023 ).…”

“…Schupp and Fuentes ( 1995 ) indicated that most vertebrate vectors that disperse seeds might play a critical ecological role in the maintenance of plant populations. Along with the observed human‐mediated habitat fragmentation threats in the grassland biome (Matsika, 2008 ; Skowno et al, 2019 ; Vukeya et al, 2023 ), the quality of dispersed seeds for particular threatened plant species is ecologically important because it allows the identification of the legitimate dispersal agents. In such research, it is essential to simulate different seed dispersal mutualism networks for the sustainability and development of biodiversity conservation's adaptive management strategies.…”