Beauty from Ashes:short term postfire regeneration of dune fynbos -thicket vegetation in the South Eastern Cape floristic region
- Authors: Gcina, Sinenjongo
- Date: 2022-12
- Subjects: Fynbos ecology – Nelson Mandela University Campus Nature Reserve , Forest fires -- Prevention and control
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59666 , vital:62319
- Description: Aim This study aims to provide an understanding and a description of the short-term postfire regeneration and ecology of the fynbos-thicket vegetation on a coastal dune system in the southeastern Cape Floristic Region. Another aim is to assess the recovery of the vegetation community by assessing the growth forms and the disturbance response across a range of species from thicket and fynbos communities and to provide a belowground bud bank classification for each of these species in the coastal dune systems. Location The study site was the Mandela University Reserve and the Noordhoek dune fields, situated in Gqeberha, Eastern Cape, which is part of the south-eastern Cape Floristic Region. The study site hosts thicket-fynbos mosaic vegetation type that occurs in a Mediterranean-Climate Ecosystem (MCE). Methods Firstly, field observations and photographs of plant species were taken weekly to assess and identify the species that were emerging and persisting in the dune system in the first 12 months postfire. Phenological events of the species that emerged (e.g., flowering, fruiting, leaf growth, leaf yellowing, and leaf abscission) were also observed and reported on. Secondly, an excavation of 21 species (e.g., Jamesbrittenia microphylla, Euclea racemosa, Olea exasperata, Searsia laevigata) was conducted to classify the species into their belowground bud bank types. Results There was a rapid emergence of resprouters (facultative resprouters and obligate resprouters) in the first 12 months postfire. This was followed by their growth; primarily occurring after the rainfall events. The dominant resprouting species (facultative resprouters and obligate resprouters) entered the system two weeks after the fire. There was a significant difference in the time to the first emergence of the different regeneration groups postfire (P < 0.001): on average, obligate sprouters (OS) appeared 1 month after fire – two months earlier than facultative sprouters (FS) and four months earlier than non-sprouters (NS). There was no statistical evidence to suggest that the FS and non-sprouters NS emerged at different times postfire; however, most NS species were observed in the system 5 months after fire. 4 Exceptions were the NS species Pelargonium grossularoides and Mesembryanthemum aitonis, both annuals that emerged 1 month after fire. A wide range of OS species that appeared earlier in the system (e.g., Euclea racemosa, Olea exasperata, Searsia laevigata, and Lauridia tetragona) exhibit underground lateral growth with belowground bud banks (BBBs) from which they recover after disturbance. In total, six BBB types were recorded in this study, namely: bud-bearing root, rhizome, rhizophore, woody rhizome, stem tuber, and corms. The bud-bearing root from woody species was the dominant BBB in this system. Main conclusion The return of species that occurs in the first year after fire occurs rapidly in the first 2 months as resprouting species (primarily OS) appear in the system. Following this, the rate of return of species decreases as reseeding species (primarily NS) gradually reestablish and occupy the gaps in the dune fynbos-thicket vegetation. This study has shown that plant species in this ecosystem are adapted to fire disturbance as their populations are able to reestablish through various regeneration strategies, including resprouting from different types of BBB. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Gcina, Sinenjongo
- Date: 2022-12
- Subjects: Fynbos ecology – Nelson Mandela University Campus Nature Reserve , Forest fires -- Prevention and control
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59666 , vital:62319
- Description: Aim This study aims to provide an understanding and a description of the short-term postfire regeneration and ecology of the fynbos-thicket vegetation on a coastal dune system in the southeastern Cape Floristic Region. Another aim is to assess the recovery of the vegetation community by assessing the growth forms and the disturbance response across a range of species from thicket and fynbos communities and to provide a belowground bud bank classification for each of these species in the coastal dune systems. Location The study site was the Mandela University Reserve and the Noordhoek dune fields, situated in Gqeberha, Eastern Cape, which is part of the south-eastern Cape Floristic Region. The study site hosts thicket-fynbos mosaic vegetation type that occurs in a Mediterranean-Climate Ecosystem (MCE). Methods Firstly, field observations and photographs of plant species were taken weekly to assess and identify the species that were emerging and persisting in the dune system in the first 12 months postfire. Phenological events of the species that emerged (e.g., flowering, fruiting, leaf growth, leaf yellowing, and leaf abscission) were also observed and reported on. Secondly, an excavation of 21 species (e.g., Jamesbrittenia microphylla, Euclea racemosa, Olea exasperata, Searsia laevigata) was conducted to classify the species into their belowground bud bank types. Results There was a rapid emergence of resprouters (facultative resprouters and obligate resprouters) in the first 12 months postfire. This was followed by their growth; primarily occurring after the rainfall events. The dominant resprouting species (facultative resprouters and obligate resprouters) entered the system two weeks after the fire. There was a significant difference in the time to the first emergence of the different regeneration groups postfire (P < 0.001): on average, obligate sprouters (OS) appeared 1 month after fire – two months earlier than facultative sprouters (FS) and four months earlier than non-sprouters (NS). There was no statistical evidence to suggest that the FS and non-sprouters NS emerged at different times postfire; however, most NS species were observed in the system 5 months after fire. 4 Exceptions were the NS species Pelargonium grossularoides and Mesembryanthemum aitonis, both annuals that emerged 1 month after fire. A wide range of OS species that appeared earlier in the system (e.g., Euclea racemosa, Olea exasperata, Searsia laevigata, and Lauridia tetragona) exhibit underground lateral growth with belowground bud banks (BBBs) from which they recover after disturbance. In total, six BBB types were recorded in this study, namely: bud-bearing root, rhizome, rhizophore, woody rhizome, stem tuber, and corms. The bud-bearing root from woody species was the dominant BBB in this system. Main conclusion The return of species that occurs in the first year after fire occurs rapidly in the first 2 months as resprouting species (primarily OS) appear in the system. Following this, the rate of return of species decreases as reseeding species (primarily NS) gradually reestablish and occupy the gaps in the dune fynbos-thicket vegetation. This study has shown that plant species in this ecosystem are adapted to fire disturbance as their populations are able to reestablish through various regeneration strategies, including resprouting from different types of BBB. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Flammability of indigenous and invasive alien woody plants in coastal fynbos and thicket
- Msweli, Samukelisiwe Tholakele, Potts, Alastair J
- Authors: Msweli, Samukelisiwe Tholakele , Potts, Alastair J
- Date: 2020
- Subjects: Forest fires -- Environmental aspects , Forest fires -- Prevention and control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45875 , vital:39313
- Description: Globally, extreme fires have become more common in wildland-urban interface areas, and more recently, along the southern Cape coast of South Africa. The 2017 Knysna fires prompted greater understanding of the flammability of, and the fire risk posed by, different vegetation groups, which is essential to develop fire risk mitigation strategies. In this study, I experimentally assessed flammability of 30 woody plant species from the vegetation groups indigenous fynbos, thicket, and invasive alien plants (IAPs) that occur along the southern Cape coast. Live plant shoots were sampled across varying fire weather conditions and burnt experimentally to measure flammability in relation to fire weather conditions, fuel moisture, and fuel load. Flammability measures considered were: burn intensity, completeness of burn, time-to-ignition, and the likelihood of spontaneous ignition. I further assessed the flammability of partially dried plant material as a crude proxy for drought effects, to ascertain whether drying of fuels would differentially affect the flammability of the vegetation groups. I used generalized linear mixed-effects models to assess flammability measures in relation to the predictor variables: fire weather, fuel moisture, fuel load, vegetation groups, and species (as a random factor). Results showed that increasing severity of fire weather significantly increased flammability through increasing burn intensity, increasing completeness of burn, increasing the likelihood of spontaneous ignition, and also reducing time-to-ignition. Increasing fuel moisture significantly decreased burn intensity, completeness of burn, and the likelihood of spontaneous ignition. Fuel load significantly increased burn intensity and time-to-ignition. Flammability was highest in IAPs, intermediate in fynbos, and lowest in thicket. IAPs and fynbos showed significantly higher ignitability, and thus present risks under moderate and high fire weather conditions, whereas thicket presents lower risks under low and moderate fire weather conditions. The drying out of fuels considerably increased flammability equally in the three vegetation groups, and by implication, fire risk due to an increase in dead:live ratio. Flammability was furthermore assessed in relation to fuel traits, i.e. the proportion of fine fuels, coarse fuels, and dead fuels, fuel bed porosity, fuel load, and fuel moisture, using multiple regression analysis and stepwise selection of factors. This revealed that fuel moisture was the most important factor affecting flammability in terms of all the flammability measures. Results further showed that the increase in v the proportions of fine fuels increased flammability by increasing completeness of burn. Lastly, vegetation groups were compared (using Kruskal Wallis) in terms of their flammability and fuel traits. I found that fynbos and IAPs exhibited greater flammability on account of higher completeness of burn and more rapid ignition than thicket species, but no clear distinction was evident between fynbos and IAPs. Fynbos’ high flammability was attributed to high proportions of fine and porous fuels. Thicket’s low flammability was attributed to high proportions of coarse and dense fuels. Little distinction in fuel traits could be made between fynbos and IAPs, except that fynbos had a greater proportion of fine fuels. There is a potential risk posed by the IAPs in terms of increased flammability and fire severity, on an indigenous landscape that is invaded. Fire managers need to encourage the prioritization of the management of IAPs that present high flammability as an attempt to reduce fire risk along the southern Cape coast of South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Msweli, Samukelisiwe Tholakele , Potts, Alastair J
- Date: 2020
- Subjects: Forest fires -- Environmental aspects , Forest fires -- Prevention and control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45875 , vital:39313
- Description: Globally, extreme fires have become more common in wildland-urban interface areas, and more recently, along the southern Cape coast of South Africa. The 2017 Knysna fires prompted greater understanding of the flammability of, and the fire risk posed by, different vegetation groups, which is essential to develop fire risk mitigation strategies. In this study, I experimentally assessed flammability of 30 woody plant species from the vegetation groups indigenous fynbos, thicket, and invasive alien plants (IAPs) that occur along the southern Cape coast. Live plant shoots were sampled across varying fire weather conditions and burnt experimentally to measure flammability in relation to fire weather conditions, fuel moisture, and fuel load. Flammability measures considered were: burn intensity, completeness of burn, time-to-ignition, and the likelihood of spontaneous ignition. I further assessed the flammability of partially dried plant material as a crude proxy for drought effects, to ascertain whether drying of fuels would differentially affect the flammability of the vegetation groups. I used generalized linear mixed-effects models to assess flammability measures in relation to the predictor variables: fire weather, fuel moisture, fuel load, vegetation groups, and species (as a random factor). Results showed that increasing severity of fire weather significantly increased flammability through increasing burn intensity, increasing completeness of burn, increasing the likelihood of spontaneous ignition, and also reducing time-to-ignition. Increasing fuel moisture significantly decreased burn intensity, completeness of burn, and the likelihood of spontaneous ignition. Fuel load significantly increased burn intensity and time-to-ignition. Flammability was highest in IAPs, intermediate in fynbos, and lowest in thicket. IAPs and fynbos showed significantly higher ignitability, and thus present risks under moderate and high fire weather conditions, whereas thicket presents lower risks under low and moderate fire weather conditions. The drying out of fuels considerably increased flammability equally in the three vegetation groups, and by implication, fire risk due to an increase in dead:live ratio. Flammability was furthermore assessed in relation to fuel traits, i.e. the proportion of fine fuels, coarse fuels, and dead fuels, fuel bed porosity, fuel load, and fuel moisture, using multiple regression analysis and stepwise selection of factors. This revealed that fuel moisture was the most important factor affecting flammability in terms of all the flammability measures. Results further showed that the increase in v the proportions of fine fuels increased flammability by increasing completeness of burn. Lastly, vegetation groups were compared (using Kruskal Wallis) in terms of their flammability and fuel traits. I found that fynbos and IAPs exhibited greater flammability on account of higher completeness of burn and more rapid ignition than thicket species, but no clear distinction was evident between fynbos and IAPs. Fynbos’ high flammability was attributed to high proportions of fine and porous fuels. Thicket’s low flammability was attributed to high proportions of coarse and dense fuels. Little distinction in fuel traits could be made between fynbos and IAPs, except that fynbos had a greater proportion of fine fuels. There is a potential risk posed by the IAPs in terms of increased flammability and fire severity, on an indigenous landscape that is invaded. Fire managers need to encourage the prioritization of the management of IAPs that present high flammability as an attempt to reduce fire risk along the southern Cape coast of South Africa.
- Full Text:
- Date Issued: 2020
- «
- ‹
- 1
- ›
- »