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Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits
Thesis (PhD)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613805681311744 |
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| access_status_str | Open Access |
| author | Fisher, Ruth-Mary Corne |
| author2 | Roets, Francois |
| author_browse | Fisher, Ruth-Mary Corne Roets, Francois |
| author_facet | Roets, Francois Fisher, Ruth-Mary Corne |
| author_sort | Fisher, Ruth-Mary Corne |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132123 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:59.323Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132123 Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits Fisher, Ruth-Mary Corne Roets, Francois Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology & Entomology. Fynbos ecology Soil hydrophobicity Soil moisture -- Measurement Vegetation and climate -- South Africa -- Agulhas -- Protected Areas Fynbos -- Soils -- Adaptation -- South Africa --Agulhas -- Table Mountain National Parks Invasive plants -- South Africa -- Geographical distribution Alien plants -- South Africa -- Geographical distribution Fynbos -- Effect of fires on -- South Africa Vegetation management -- South Africa -- Western Cape National parks and reserves -- South Africa -- Table Mountain (Western Cape) UCTD Thesis (PhD)--Stellenbosch University, 2025. Fisher, R. C. 2025. Soil hydrophobicity in Fynbos: Measuring the impacts of woody invasive alien plant species and fire and ecological benefits. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/309dbaa6-6e16-45fd-ace6-55082444366c ENGLISH ABSTRACT: Soil hydrophobicity is a condition where the soil does not wet spontaneously when water is placed on the surface. This is due to particles becoming coated with oily hydrophobic substances originating from above-ground vegetation and produced by soil micro-organisms. This phenomenon has been well-studied in Mediterranean-type ecosystems (MTEs), but knowledge is limited Fynbos, a MTE, in South Africa. Factors such as vegetation type and structure, organic matter, fire, soil texture, and soil moisture play a role in the occurrence, severity, and spatial-temporal distribution of soil hydrophobicity. The overall aim of this thesis was to document the presence and spatial-temporal distribution of soil hydrophobicity in Fynbos ecosystems in order to explore the role in Fynbos ecology. This study, which was conducted in Agulhas and Table Mountain National Parks, has four components: 1. Determining the presence and frequency of occurrence of soil hydrophobicity in native Fynbos vegetation types and the role of vegetation type, organic matter, soil texture, and soil moisture on its spatial-temporal distribution, 2. Determining the impact of invasive alien plants (IAP) on the frequency of occurrence of hydrophobicity, 3. Determining the role of combined fire and drought on the occurrence and severity of hydrophobicity and 4. Determining the role of soil hydrophobicity, fire, and drought on post-fire fynbos vegetation succession. Soil hydrophobicity was detected at different frequencies of occurrence in five out of six native fynbos vegetation types and under IAP. A combination of vegetation structure, organic matter, and soil texture played a role in its distribution. Soil hydrophobicity was also temporal with the highest occurrences and severity during the dry hot summer months. Vertically, the surface soil up to 20 mm depth was less hydrophobic than the deeper soil depths. A planned burn affected soil hydrophobicity differently across the vegetation types, i.e., the fire reduced soil hydrophobicity at the soil surface of the Protea-dominated site, but not the Restio-dominated site. However, the effects of the fire on hydrophobicity were short-lived. The evolution of soil hydrophobicity over time after fire was driven by soil moisture. During a drought in April 2015, the deeper, mostly wettable 50 and 100 mm soil depths at the Restio-dominated site, became hydrophobic to the same extent and severity as the other normally hydrophobic sites. Post-fire changes in vegetation communities were as expected in Fynbos ecosystems. However, the drought and prolonged hydrophobic status of the soil resulted in localized seedling and adult mortalities. Management recommendations included: i) the mapping of the hydrophobic status of soils to aid in erosion risk assessments, ii) managers of Fynbos-protected areas to work together with climate change scientists in planning the timing of prescribed burns to ensure conducive post-fire climatic conditions for optimal post-fire vegetation recovery and succession, and iii) where possible, to invest in long-term post-fire vegetation succession monitoring. I also provide a conceptual model describing the role of soil hydrophobicity in Fynbos ecology. AFRIKAANSE OPSOMMING: Grondhidrofobisiteit is 'n toestand waar die grond nie spontaan benat wanneer water op die oppervlak geplaas word nie. Dit is as gevolg van partikels wat bedek word met olierige hidrofobiese stowwe afkomstig vanaf bogrondse plantegroei en stowwe vervaardig deur grondorganismes. Hierdie verskynsel is goed bestudeer in Mediterreense-tipe ekosisteme (MTE's), maar kennis is beperk in Fynbos, 'n MTE, in Suid-Afrika. Faktore soos plantegroeitipe en -struktuur, organiese materiaal, brand, grondtekstuur en grondvog speel 'n rol in die voorkoms, erns en ruimtelike-temporele verspreiding van grondhidrofobisiteit. Die oorhoofse doel van hierdie tesis was om die teenwoordigheid en ruimtelike-temporele verspreiding van grondhidrofobisiteit in Fynbos-ekosisteme in die Agulhas- en Tafelberg Nasionale Parke en die rol van grondhidrofobisiteit in Fynbosekologie te dokumenteer. Hierdie studie het vier komponente: 1. Bepaling van die teenwoordigheid en frekwensie van voorkoms van grondhidrofobisiteit in inheemse Fynbos-plantegroeitipes en die rol van plantegroeitipe, organiese materiaal, grondtekstuur en grondvog op die ruimtelike-temporele verspreiding daarvan, 2. Bepaling van die impak van uitheemse indringerplante (IAP) op die frekwensie van voorkoms van hidrofobisiteit, 3. Bepaling van die rol van brand en droogte op die voorkoms en erns van hidrofobisiteit en 4. Bepaling van die rol van grondhidrofobisiteit, brand en droogte op na-brand Fynbos plantegroei opeenvolging. Grondhidrofobisiteit is gevind by verskillende voorkomsfrekwensies in vyf uit ses inheemse Fynbos-plantegroeitipes en onder IAP. 'n Kombinasie van plantegroeistruktuur, organiese materiaal en grondtekstuur het 'n rol in die verspreiding daarvan gespeel. . Gronhidrofobisiteit was tydelik, het die meeste voorgekom en het die hoogste intensiteit gehad gedurende die droë somermaande. Vertikaal was die oppervlakgrond tot 20 mm diepte minder hidrofobies as die dieper gronddieptes. 'n Beplande brande het grondhidrofobisiteit verskillend beïnvloed oor die plantegroeitipes. Die brand het grondhidrofobisiteit by die grondoppervlak van die Restio-gedomineerde terrein geïnduseer, maar nie die Protea-gedomineerde terrein nie. Die uitwerking van die brand op hidrofobisiteit was egter van korte duur. Die evolusie van grondhidrofobisiteit oor tyd sedert brand is deur grondvog aangedryf is. Tydens 'n droogte in April 2015 het die dieper, meestal benatbare 50 en 100 mm gronddieptes in die Restio-gedomineerde terrein hidrofobies geword en dieselfde intensiteit gehad as die ander normaalweg hidrofobiese terreine. Na-brand veranderinge in plantegroei gemeenskappe was soos verwag in Fynbos ekosisteme. Die droogte en langdurige hidrofobiese status van die grond het egter gelei tot gelokaliseerde saailing- en volwasse- mortaliteite. Bestuursaanbevelings het die insluiting van kartering van die hidrofobiese status van gronde ingesluit om te help met erosie-risiko-assesserings, bestuurders van Fynbos-beskermde gebiede om saam met klimaatsveranderingwetenskaplikes te werk in die beplanning van die tydsberekening van voorgeskrewe brandwonde om bevorderlike klimaatstoestande na-brand te verseker vir optimale herwinning en opvolging van plantegroei na-brand, en waar moontlik, om te belê in langtermyn-monitering van na-brande plantegroei opvolg. Ek verskaf ook 'n konseptuele model wat die rol van grondhidrofobisiteit in Fynbosekologie beskryf. Doctoral 2025-05-26T08:17:43Z 2025-05-26T08:17:43Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132123 en Stellenbosch University xvi, 156 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Fynbos ecology Soil hydrophobicity Soil moisture -- Measurement Vegetation and climate -- South Africa -- Agulhas -- Protected Areas Fynbos -- Soils -- Adaptation -- South Africa --Agulhas -- Table Mountain National Parks Invasive plants -- South Africa -- Geographical distribution Alien plants -- South Africa -- Geographical distribution Fynbos -- Effect of fires on -- South Africa Vegetation management -- South Africa -- Western Cape National parks and reserves -- South Africa -- Table Mountain (Western Cape) UCTD Fisher, Ruth-Mary Corne Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| title | Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| title_full | Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| title_fullStr | Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| title_full_unstemmed | Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| title_short | Soil hydrophobicity in fynbos: measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| title_sort | soil hydrophobicity in fynbos measuring the impacts of woody invasive alien plant species and fire and ecological benefits |
| topic | Fynbos ecology Soil hydrophobicity Soil moisture -- Measurement Vegetation and climate -- South Africa -- Agulhas -- Protected Areas Fynbos -- Soils -- Adaptation -- South Africa --Agulhas -- Table Mountain National Parks Invasive plants -- South Africa -- Geographical distribution Alien plants -- South Africa -- Geographical distribution Fynbos -- Effect of fires on -- South Africa Vegetation management -- South Africa -- Western Cape National parks and reserves -- South Africa -- Table Mountain (Western Cape) UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132123 |
| work_keys_str_mv | AT fisherruthmarycorne soilhydrophobicityinfynbosmeasuringtheimpactsofwoodyinvasivealienplantspeciesandfireandecologicalbenefits |