Browsing by Author "Van Schalkwyk, Julia"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Beta diversity across the complementary zones of the Kogelberg Biosphere Reserve
    (Stellenbosch : Stellenbosch University, 2019-04) Van Schalkwyk, Julia; Pryke, James S.; Samways, Michael J.; Gaigher, Rene; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Biodiversity loss is occurring at an alarming rate. Protected areas alone are not sufficient for long-term biodiversity conservation. To address this, conservation efforts need to incorporate the landscape surrounding protected areas. Biosphere reserves (BR) consist of three zones with different (but complementary) functions: a core area (dedicated specifically to long-term biodiversity conservation), an adjoining buffer zone (where activities should be compatible with the objectives of the core), and a flexible transition zone (where sustainable resource use and management is promoted). Zonation will generally match existing land-use patterns, and the buffer forms part of a continuous but increasing gradient of land-use intensity (LUI) as one moves away from the core. The aim of this study is to assess the success of biodiversity conservation of the different zones of the Kogelberg Biosphere Reserve (KBR) in response to increasing LUI away from the core. I focused on commercial fruit farming, since it is an important economic activity in the study area. I chose objectives that are related to the ecological function of each zone using arthropods as study organisms, and employed principles based on systematic conservation planning (SCP) and landscape ecology. The specific objectives were: 1) to determine whether arthropod diversity tracks plant diversity, 2) assess how well arthropod diversity is represented in the core zone, 3) to determine whether the buffer zone is effective in protecting the core from activities in the transition, 4) to assess whether the buffer zone complements arthropod diversity in the core zone, 5) to assess how orchards influence arthropod diversity in adjacent non-crop habitats, and 6) to determine how LUI at different spatial scales affects arthropod diversity within orchards. The results showed that arthropod diversity is relatively well-represented within the core zone, but that the buffer has important complementary value by adding ecological environments not present in the core. The buffer also improves the comprehensiveness of the reserve by establishing strong environmental gradients (which are important for congruence in plant and arthropod diversity). The KBR does not have a continuous buffer surrounding its core area, and this was reflected by the influence of anthropogenic activities (i.e. proximity to deciduous fruit orchards) on diversity in the core zone. This influence reached up to 1 km away from orchards, decreasing the effective conservation area of the core zone where the buffer is absent or not wide enough. Closer investigation showed that the observed edge responses were the result of differential responses of different arthropod groups, and that they could be predicted by traits related to species habitat specialization (species which prefer natural habitats, species which prefer orchards, and species which occur in either). The results highlighted the variegated nature of the transformed landscapes that is not captured by patch-orientated views of fragmentation. This study also emphasises the importance of management actions within orchards on diversity in adjacent habitats and the associated non-visible heterogeneity. Arthropod diversity in orchards showed contrasting responses to increasing LUI at different spatial scales. Local LUI (management intensity) had a negative influence on some groups. Landscape scale LUI (in the form of more orchards in the landscape) increased species richness of a subset of species, and contributed to the homogenization of orchard arthropod diversity across the landscape. This highlights the need to consider the influence of LUI on diversity at different spatial scales. Principles from SCP and landscape ecology are valuable for prioritizing conservation efforts, and for guiding planning and management towards promoting biodiversity across the entire landscape. To enhance arthropod diversity across the KBR, the most important recommendations from this study are to include a range of abiotic variables (especially variables related to climate and geology) in conservation areas. This implies conservation efforts should not be restricted to only the core zone. While LUI was important in determining diversity at the local scale, non-crop habitats are essential for enhancing farmland diversity across the entire BR.
  • Thumbnail Image
    Item
    Biodiversity conservation in a fragmented landscape : arthropod assemblages in smaller corridors within a production landscape
    (Stellenbosch : Stellenbosch University, 2015-04) Van Schalkwyk, Julia; Pryke, James S.; Samways, Michael J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Habitat loss and fragmentation are major threats to global biodiversity. A cornerstone of traditional conservation involves setting aside land as formally protected areas (PAs). However, for effective biological conservation in the long term there needs to be connectivity between these PAs. When possible, improved connectivity can be achieved using natural corridors at a landscape scale. Even better is to establish a network of corridors and nodes in the form of ecological networks (ENs). ENs are currently being employed by commercial forestry companies in South Africa. While larger corridors and nodes are considered optimum, factors other than design, such as management and environmental heterogeneity, have also been found to be important for species maintenance. This study aims to explore the role of corridor width in driving the composition of invertebrate assemblages across a transformed landscape in KwaZulu-Natal, South Africa, and to investigate other possible environmental variables significant for species distributions. In Chapter 2, I investigated the contribution of smaller grassland corridors within a timber production matrix to overall biodiversity conservation using two important bioindicator taxa. Ants and dung beetles were sampled in grassland corridors of three size classes, plantation blocks and a nearby PA, iMpendle Nature Reserve. The two taxa showed differential responses to landscape level fragmentation. Dung beetles showed a decrease in species richness and corresponding increase in species turnover with increased fragmentation, while ants were unaffected, although counter intuitively smaller corridors even contained more unique ant species compared to larger corridors. Dung beetle assemblages also showed strong differences between the PA and grassland corridors. While the conservation effectiveness of large corridors undoubtedly exceeds that of smaller corridors, for ants it seems that smaller corridors contribute to their overall conservation within this production landscape. In Chapter 3, I explore the importance of spatial and environmental factors for species distribution across this landscape. Dung beetles were split into functional guilds according to size and nesting behaviour for analyses. Within grassland corridors, tunnelling dung beetle species richness was sensitive to landscape level fragmentation, especially for larger species, while elevation and vegetation type influenced ant species richness. Since rolling dung beetles showed a close association with the PA, the marked difference in dung beetle assemblages between these two land-uses may be due to the presence of pellet producing grazers in the protected area and their replacement by pat producing cattle in the grassland corridors. Other environmental variables that were found to be important for dung beetle species composition were elevation, vegetation type, and soil hardness. For ant species composition, only elevation was found to be important. In conclusion, as large corridors were comparable to the PA in dung beetle and ant species richness, ENs act as extensions of formally PAs, given that they are large enough. Nevertheless, smaller corridors had surprisingly high species richness. Including additional information other than species data improved our knowledge of the underlying factors that drive dung beetle species composition. Even though dung beetle and ant species responded differentially to habitat fragmentation, environmental heterogeneity seemed important for both taxa. Incorporating habitat heterogeneity into the current management scheme may improve the conservation effectiveness within this transformed landscape.