Beta diversity across the complementary zones of the Kogelberg Biosphere Reserve

[摘要] 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.

[发布机构] Stellenbosch University