Doctoral Degrees (Conservation Ecology and Entomology)
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Browsing Doctoral Degrees (Conservation Ecology and Entomology) by Subject "Agriculture -- Environmental aspects"
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- ItemViticultural effects on arthropod diversity in the Cape Winelands Biosphere Reserve(Stellenbosch : Stellenbosch University, 2021-03) Geldenhuys, Marinus; Gaigher, Rene; Pryke, James S.; Samways, Michael J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Agricultural land-use intensification negatively impacts biodiversity, ecosystem function, and ecosystem services at local and global scales. Biosphere reserves consist of interrelated and complementary zones of different land-use intensity, are important platforms for integrating human-environment interactions, and support effective conservation through bridging the gap between conservation science, practitioners, and other stakeholders. This study assesses the success status of arthropod conservation within the Cape Winelands Biosphere Reserve (CWBR), a biosphere reserve situated in a global biodiversity hotspot where viticulture is the dominant agricultural land use. The focus is on viticultural management practices and their interactions with the surrounding landscape at multiple spatial scales. Assessment of a wide range of viticultural management practices and environmental variables at the local scale, showed that arthropod species richness can be enhanced through maintaining herbaceous vegetation in vineyard inter-rows, and by leaving plant litter on the vineyard floor. The results were consistent across different management regimes and landscape contexts, emphasising the broad applicability of this agro-ecological approach at the local scale, which also aligns with global trends in plant diversification in perennial crops. At the larger, farm scale, there was limited spillover of stenotopic species associated with remnant fynbos vegetation into vineyards, and no variables were identified that could enhance their spillover. This suggests that proximity of remnant patches, stepping-stone habitats, and conservation corridors may be important for improving functional landscape connectivity for these stenotopic arthropods across this vineyard mosaic. Nonetheless, ubiquitous arthropods in vineyards benefited from increased herbaceous vegetation in the inter-rows. Conversely, there was some spillover of cultural species from vineyards into fynbos, and the ecosystem consequences of this requires further investigation. Furthermore, contrary to main trends in the literature, I found no mediating effects of landscape complexity on local-scale practices (increased vegetation cover and organic farming) with regard to arthropod species richness. However, there were strong interacting effects of organic farming and landscape complexity on arthropod assemblages within vineyards, with greater assemblage dissimilarity among organic farms along a landscape complexity gradient, than among integrated farms. Lastly, at a regional scale, vineyards were nearly equal to natural vegetation in terms of alpha and beta diversity, but vineyards had significantly lower functional diversity. There were significant differences in fynbos and vineyard assemblages. Additionally, there were strong trait associations of predatory beetles with vineyards, as well as smaller sized beetles and plant- dwelling spiders to natural vegetation, indicating a shift in assemblage trait composition between natural and cultivated areas. Deviations from main trends in the literature here highlight the natural variation among different regions, and the importance of site-specific studies for the assessment of arthropod responses to local conditions. Vineyards in the CWBR show great potential for supporting diverse and abundant arthropod assemblages that are functionally dissimilar from the surrounding natural species pool, in-turn contributing to heterogeneity across the landscape. Furthermore, there are opportunities for enhancing arthropod diversity within vineyards, benefitting wine production. The results also emphasise the value of biodiversity conservation in the buffer and transition zones of the CWBR, and in biosphere reserves in general.