Beta Diversity Across the Complementary Zones of the Kogelberg Biosphere Reserve
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Beta Diversity across the Complementary Zones of the Kogelberg Biosphere Reserve by Julia van Schalkwyk Dissertation presented for the degree of Doctor of Philosophy (Science) at Stellenbosch University Department of Conservation Ecology and Entomology, Faculty of AgriSciences Supervisor: Dr. James S. Pryke Co-supervisor: Prof. Michael J. Samways Co-supervisor: Dr. René Gaigher April 2019 Stellenbosch University https://scholar.sun.ac.za Declaration By submitting this dissertation electronically, I declare that the entirety of the work contained therein is my own, original work, that I am the sole author thereof (save to the extent explicitly otherwise stated), that reproduction and publication thereof by Stellenbosch University will not infringe any third party rights and that I have not previously in its entirety or in part submitted it for obtaining any qualification. Date: April 2019 Copyright © 2019 Stellenbosch University All rights reserved i Stellenbosch University https://scholar.sun.ac.za General summary 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 ii Stellenbosch University https://scholar.sun.ac.za 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. iii Stellenbosch University https://scholar.sun.ac.za Algemene opsomming Biodiversiteitsverlies vind plaas teen 'n onrusbarende tempo. Beskermde gebiede alleenlik is nie voldoende vir langtermyn biodiversiteitsbewaring nie. Om dit teen te werk moet bewaringspogings die landskap rondom beskermde gebiede insluit. Biosfeerreservate bestaan uit drie sones met verskillende (maar komplementêre) funksies: ‘n kerngebied (spesifiek toegewy aan langtermyn biodiversiteitsbewaring), 'n aangrensende buffersone (waar aktiwiteite verenigbaar moet wees met die doelwitte van kerngebied) en 'n buigsame oorgangsone (waar volhoubare hulpbrongebruik en bestuur bevorder word). Sonering sal oor die algemeen met bestaande grondgebruikspatrone ooreenstem, en die buffersone vorm deel van ‘n deurlopende en toenemende gradiënt van grondgebruik intensiteit (GI) met toenemde afstand vanaf die kerngebied. Die doel van hierdie studie was om die biodiversiteitsbewaringssukses van die verskillende sones van die Kogelberg-biosfeerreservaat te beoordeel in reaksie op toenemende GI weg van kerngebied. Ek het gefokus op kommersiële vrugteboerdery, aangesien dit 'n belangrike ekonomiese aktiwiteit in die studiegebied is. Ek het subvrae ondersoek wat verband hou met die ekologiese funksie van elke sone met behulp van geleedpotiges as studie-organismes en beginsels gebaseer op sistematiese bewaringsbeplanning (SB) en landskapekologie. Die spesifieke doelwitte was: 1) bepaal of plantdiversiteit die diversiteit van geleedpotiges reflekteer, 2) beoordeel hoe goed geleedpotige diversiteit in kerngebiede verteenwoordig word, 3) bepaal of die buffersone effektief is om die kerngebied van aktiwiteite in die oorgangsone te beskerm, 4) assesseer of buffergebiede die geleedpotige diversiteit in die kerngebiede aanvul, 5) beoordeel hoe boorde geleedpotige diversiteit in aangrensende nie-gewas habitatte beïnvloed, en 6) bepaal hoe GI oor verskillende ruimtelike skale die diversiteit van geleedpotiges binne boorde affekteer. Die resultate het gewys dat geleedpotige diversiteit relatief goed verteenwoordig word in kerngebiede, maar dat die buffersones ‘n belangrike aanvullende rol speel deur ekologiese omgewings wat nie in die kerngebiede voorkom nie by te voeg, en ook die volledigheid van die reservaat verbeter deur sterk omgewingsgradiënte te vestig (wat belangrik is vir kongruensie in plant- en geleedpotige diversiteit). Die Kogelberg-biosfeerreservaat het nie 'n deurlopende buffersone rondom sy kerngebied nie, en dit was weerspieël deur die invloed van menslike aktiwiteite (d.w.s. nabyheid aan vrugteboorde) op diversiteit in kerngebiede. Hierdie invloed het tot 1 km weg van boorde iv Stellenbosch University https://scholar.sun.ac.za gestrek, en waar die buffersone afwesig was of nie wyd genoeg was nie het dit gelei tot ‘n kleiner effektiewe bewaringsgebied in kerngebiede. Nadere ondersoek het getoon dat die waargenome randreaksies die gevolg was van differensiële reaksies van geleedpotige groepe wat voorspel kon word deur eienskappe wat verband hou met habitat-spesialisasie (spesies wat natuurlike habitatte verkies, spesies wat boorde verkies en spesies wat voorkom in óf natuurlike habitatte of boorde). Die resultate het die gesofistikeerde aard van getransformeerde landskappe beklemtoon wat nie deur lappiesland-georiënteerde sienings van fragmentering vasgevang word nie. Hierdie studie beklemtoon ook die belangrikheid van bestuursaksies binne boorde vir diversiteit in aangrensende natuurlike habitatte en die gepaardgaande verborge heterogeniteit. Geleedpotige diversiteit in boorde het kontrasterende reaksies op toenemende GI op verskillende ruimtelike skale getoon. Die resultate dui daarop dat plaaslike GI (bestuursintensiteit) 'n negatiewe invloed op sommige groepe het. Landskapskaal GI (in die vorm van meer boorde in die landskap) het die spesiesrykheid van 'n deelversameling spesies verhoog en bygedra tot die homogenisering van geleedpotige diversiteit in boorde oor die landskap. Die resultate beklemtoon dat die invloed van GI op diversiteit op verskillende ruimtelike skale oorweeg moet word. Beginsels van SB en landskapsekologie