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Seasonal physiological responses in the Cape Rockjumper (Chaetops frenatus): a Fynbos endemic bird shows limited capacity to deal with temperature extremesOswald, Krista Natasha January 2016 (has links)
The Fynbos biome in south-western South Africa is a global biodiversity hotspot vulnerable to climate change. Of the six Fynbos-endemic passerines, Cape Rockjumpers (hereafter Rockjumpers; Chaetops frenatus) are most vulnerable to increases in temperature, with population declines correlated with warming, and low physiological heat thresholds. Rockjumper’s preferred mountain habitat is predicted to decrease as they lack opportunity to move to cooler regions as temperatures warm. As Rockjumpers currently occupy the coldest regions of the Fynbos, I hypothesized their thermal physiology would show cold adaptation at the expense of lowered ability to cope with higher temperatures. I aimed to determine the seasonal 1) maintenance metabolism and cold tolerance, and 2) thermoregulatory responses to high temperatures of Rockjumpers. I measured seasonal maintenance metabolic rate, thermal conductance, and maximum thermogenic capacity. I also measured seasonal resting metabolic rate, evaporative water loss, evaporative cooling efficiency, and body temperature at high air temperatures. In winter, Rockjumpers had higher maximum thermogenic capacity, lower maintenance metabolic rate, and lower thermal conductance. Lower maintenance metabolic rates (and thus, lower metabolic heat production) combined with the decreased thermal conductance, confers substantial energy savings in winter. The increased winter maximum thermogenic capacity of Rockjumpers was expected, although the mean seasonal values fell below those expected for a ~ 50 g bird using a global data set, suggesting Rockjumpers are not especially cold tolerant. I further show that in summer Rockjumpers had higher elevations in resting metabolic rates, evaporative water loss, and body temperature, denoting higher rates of heat production and lower heat thresholds in summer compared to winter. My results suggest that Rockjumpers are best suited for relatively mild Krista Oswald Dissertation Chapter 1: General Introduction temperatures. While I found further support for a physiological basis for declining Rockjumper populations, further studies on other mechanisms Rockjumpers may possess to cope with climate warming (e.g. behavioural adjustments) are needed in order to truly understand their vulnerability to climate change.
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Diversity and ecology of ophiostomatoid fungi and arthropods associated with proteaceae infructescencesRoets, Francois 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Five new species of ophiostomatoid fungi, colon ising the infructescences of
serotinous Protea species, have recently been discovered in South Africa. Prior
to this, ophostomatoid fungi were thought to be restricted to the Northern
Hemisphere. The discovery of these five species thus extensively expanded the
known geographical range of these fungi, now also to include the Southern
Hemisphere. Since this discovery, few studies have focused on the interesting
ecology of this group, which is uniquely adapted for spore dispersal by
arthropods. Studies focussed on ophiostomatoid fungi provide an unique
opportunity to study inter-organism interactions between fungi, their host plants
and the arthropods responsible for their spore dispersal. Very few similar studies
have been undertaken, particularly in the Fynbos Biome, to which most of our
economically important Protea species are confined. The current study provides
insight into some ecological aspects of these complex interactions.
The seasonal distribution of the ophiostomatoid fungi associated with the
infructescences of members of the Proteaceae was investigated. Definite
seasonal patterns were observed, with peak fungal colonisation occurring during
the wetter winter months. While determining the host specificity of these fungi, a
new Protea host for Ophiostoma splendens was identified, and a new species of
Rhyncomeliola was discovered. All ophiostomatoid species native to Fynbos in
the Stellenbosch region are exclusively associated with the infructescences of
species in the plant genus Protea.
By employing a multiplex Polymerase Chain Reaction (PCR), a set of group
specific primers was developed for the identification of South African Ophiostoma
and Gondwanamyces fungal DNA. This newly developed method was used to
scan arthropods collected from the infructescences of P. repens for the presence
of 0. splendens and G. proteae spores. By using these group-specific primers, three insects possibly responsible for long range dispersal of fungal spores were
identified. Three further insect species, possibly contributing to the short-range
dispersal of ophiostomatoid spores, were also implicated through this method.
All arthropods associated with the fruiting structures of selected members of the
Proteaceae were also investigated. A total of 62 pseudospecies (ca. 7500
individuals), belonging to 45 different arthropod families, were collected.
Proteaceae species with larger fruiting structures housed more arthropod species
and higher numbers of individuals than Proteaceae taxa with smaller fruiting
structures. Some plant species housed similar arthropod communities, while
others housed unique suites of arthropods. Seasonal patterns in arthropod
numbers were observed, and it was found that, in most instances, arthropod
numbers peaked during the autumn and winter months.
Twenty-five fungal taxa were isolated from various Proteaceae arthropods, many
of which are genera known to include Proteaceae pathogenic species.
Ophiostomatoid fungi have a saprophytic relationship with their Protea hosts, and
may deter some of these potentially harmful fungi from colon ising the
infrutescences. Some fungi showed a high degree of specificity towards potential
vectors, while others were found on a diverse range of arthropods.
This study highlights the existence of complex inter-organismal interactions
within the Fynbos Biome, a study area where the interactions between plants,
fungi and insects have been grossly neglected. The few studies that have been
conducted in this field have mostly focussed on a limited number of organisms,
and no wide-scale attempts, such as presented here, have been published. It is
important to obtain a holistic view in any ecological study that focuses on
interactions between different suites of organisms. Ultimately this will aid in the
development of better conservation strategies. This study thus provides a muchneeded
start in studies on multi-organismal interactions in the Fynbos Biome. / AFRIKAANSE OPSOMMING: Vyf nuwe ophiostoma-agtige fungus spesies is onlangs in die vrug-liggame van
Suid Afrikaanse Protea plante ontdek. Voor hierdie ontdekking, was die
algemene opvatting dat ophiostoma-agtige fungi beperk is tot die Noordelike
Halfrond. Die ontdekking van hierdie vyf spesies het dus die bekende
geografiese verspreiding van hierdie tipe fungi vergroot om nou ook die Suidelike
Halfrond in te sluit. Sederdien het min studies gefokus op die interesante
ekologie van hierdie groep, wat aangepas is vir spoorverspreiding deur
geleedpotiges. Studies wat fokus op die ophiostoma-agtige fungi voorsien 'n
unieke geleentheid om die inter-organismiese-interaksies tussen fungi, hul
gasheer plante en die geleedpotiges wat hul spore versprei, te bestudeer. Baie
min soortgelyke studies is al voorheen in die Fynbos Bioom, waar die meeste
van ons ekonomies-belangrike Protea spesies voorkom, onderneem. Die huidige
studie verleen meer inligting oor sommige ekologiese aspekte van hierdie
komplekse interaksies.
Seisoenale verspreidingspatrone van ophiostoma-agtige fungi geassosieer met
die vrug-liggame van lede van die Proteaceae, is ondersoek. Daar is defnitiewe
seisoenale patrone in die aanwesigheid van fungi gevind, met 'n piek in fungi
kolonisasie-getalle gedurende die vogtiger wintermaande. 'n Nuwe Protea
gasheer vir Ophiostoma splendens en 'n nuwe fungus spesie (Rhyncomeliola
sp.), is ontdek. Alle Fynbos ophiostoma-agtige spesies in die Stellenbosch area,
is beperk tot Protea spesies.
'n Multipleks Polimerase Ketting Reaksie is ontwikkel om die spesifieke DNS van
ophiostoma-agtige fungi te herken. Hierdie metode is gebruik om te toets vir die
aanwesigheid van spore van hierdie fungi op die liggame van geleedpotiges
(geassosieerd met P. repens). Hierdeur is drie insekte wat waarskynlik
verantwoordelik is vir die langafstand verspreiding van spore geidentifiseer. Drie verdere insekte wat moontlik verantwoordelik is vir die kortafstand verspreiding
van ophiostoma-agtige fungi is ook aangewys.
Alle geleedpotiges geassosieer met die vrugstrukture van geselekteerde lede
van die Proteaceae is ondersoek. 'n Totaal van 62 pseudo-spesies (omtrent
7500 individue), wat tot 45 families behoort, is versamel. Proteaceae spesies met
groter vrugstrukture het meer geleedpotige spesies en individue gehuisves as
taksa met kleiner vrugstrukture. Sommige plant spesies het soortgelyke
geleedpotige gemeenskappe gehuisves, terwyl unieke groepe geleedpotiges in
ander plante voorgekom het. Alhoewel die geleedpotiges seisonale variasies in
getalle geopenbaar het, het die meeste groepe 'n piek in getalle getoon
gedurende die herfs- en wintermaande.
Vyf-en-twintig fungi taksa is geïsoleer vanaf verskeie Proteaceae geleedpotiges.
Sommige van hierdie is genera wat Proteaceae patogeniese spesies insluit.
Sommige fungi het 'n hoë graad van spesifisiteit teenoor potensiële vektore
getoon, terwyl ander weer algemeen op verskeie geleedpotige spesies gevind is.
Hierdie studie dui op die bestaan van komplekse inter-organismiese-interaksies
in die Fynbos Bioom, in 'n area waar die studie van interaksies tussen plante,
fungi en insekte nog baie min aandag geniet het. Die beperkte aantal studies wat
tot dusver in hierdie veld onderneem is, fokus gewoonlik slegs op 'n paar
organismes. Geen grootskaalse studies, soos die een hier voorgelê, is al
gepubliseer nie. In enige ekologiese studie wat fokus op interaksies tussen
verskeie organismes, is dit belangrik om 'n holistiese siening te probeer verkry.
Uiteindelik sal dit bydra tot die ontwikkeling van beter bewarings-strategië.
Hierdie studie verleen dus 'n noodsaaklike begin tot studies op multiorganismiese-
interaksies.
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Biodiversity in the genus Penicillium from coastal fynbos soilVisagie, Cobus M. 12 1900 (has links)
Thesis (MSc (Microbiology))--Stellenbosch University, 2008. / Penicillium is a well‐known cosmopolitan genus with more than 225 accepted species. Species from this diverse genus, in general, are considered to primarily be soil fungi, with decomposition as its main function. Therefore, together with its ubiquitous nature, these species are of great importance in ecosystems, agriculture and biotechnology. However, in South Africa, very little research has been done on this complex genus, as species identification were often found to be problematic, even for experienced taxonomists. This lead to a number of South African studies only mentioning that a Penicillium spp. were isolated, without making any attempt of showing the extent of diversity within the genus
from the unique habitats. The present study set out to explore the extent of the species diversity in Penicillium isolated from the Cape Floristic Region, specifically focusing on coastal fynbos soil. Soil samples were collected from this region, at sites situated outside Malmesbury. Four hundred and thirty four Penicillium strains were isolated from soil‐dilutions. The strains were characterized using morphological characters and subsequently placed into 24 morphological groups. There were, also, more or less 40 strains that could not be grouped with any other isolates. Groupings were made according to conidiophore branching patterns which divided the strains into their respective subgenera. Eight species from subgenus Aspergilloides, seven from subgenus Furcatum, eight from subgenus Biverticillium and one from subgenus Penicillium were isolated. The species
were further characterized in subsequent chapters. In the second chapter of this thesis, one of the taxonomic groups in subgenus Biverticillium, isolated from coastal fynbos soil, Protea infructescences and on moth‐damaged Riesling grapes in Canada, was examined. This species was characterized using morphology and were found to have several unique characters, such as the very short synnema produced after prolonged incubation. These characters did not conform to descriptions of previously described species. Its novelty was confirmed by an ITS phylogeny and the strains were subsequently described as Penicillium ramulosum prov. nom. with P. cecidicola
and P. dendriticumas its sister taxa. In chapter three, a further seven groups belonging to Penicillium subgenus Biverticillium were characterized. These strains were identified as P. minioluteum, P. verruculosum and P. rugulosum‐like, respectively. Four of the groups showed unique morphological characters, with the ITS phylogeny resolving the fynbos strains separate from all previously described species. The strains were, therefore, considered to be new to science and described as P. solicola prov. nom., P. ptychoconidium prov. nom., P. occultum prov. nom. and P. chloroloma prov. nom., respectively. A key to species from subgenus Biverticilliumcluded.
is also inPenicillium subgenus Furcatum was the subject of the fourth chapter of this thesis. Our survey found that although the species diversity in this group was not as high as for the other subgenera, it was the group most often isolated in this study. Species were identified as P. janczewskii, P. canescens, P. melinii, P. corylophilum and P. citrinum using morphological characters. One species belonging to subgenus Penicillium, P. expansum, was also isolated and compared to species recorded during a previous survey. Amongst the identified species, were two groups that could not be identified using published keys, with their novelty confirmed by an ITS phylogeny. They are, therefore, described here as P. subturcoseum prov. nom. and P. hemitrachum prov. nom. A key to species in this
subgenus is also provided. In Chapter 5 the presence of Penicillium subgenus Aspergilloides, which is characterized by monoverticillate conidiophores, were investigated. Species were identified as P. roseopurpureum, P. restrictum, P. hirayamae and P. toxicarium. Amongst the identified species, were four groups that did not conform to previously described species and are described here as P. brachycaulon prov. nom., P. malacosphaerula prov. nom., P. cumulacinatum prov. nom. and P. vulgaris prov. nom., respectively. The newly described species have been included in a key, together with closely related species and the other species of subgenus Aspergilloides from the fynbos soil. Species identifications in Penicillium is often problematic and South African taxonomists have often not attempt to identify strains down to species level. During this study, Penicillium was found to be well represented in the soil, with a large proportion being previously undescribed. For this reason, a dichotomous and synoptic key to species isolated during this study are provided in the final chapter. This study should thus serve as a basis for further explorations into the diversity and ecological role of this group of organisms in this ecologically mportant biome.
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The ecological effect of Acacia saligna in a sand plain fynbos ecosystem of the Western Cape, South AfricaVan den Berckt, Tom 12 1900 (has links)
Thesis (MScFor)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The invasive Australian acacia, A. sa ligna, is widespread in the Western Cape, South Africa, and
is widely used by local communities. Not surprisingly, the introduction of the biological control
agent, the fungus Uromycladium tepperianum in 1987 was received with mixed emotions. In an
effort to determine the socio-economical and ecological impact of the fungus, the Department of
Water Affairs and Forestry has commissioned a study, of which this thesis forms part.
For this thesis, a number of parameters, environmental as well as biological, were sampled,
analyzed and compared with existing data from previous studies. The goal was to obtain a
comprehensive estimation of the effect of A. saligna on a Sand Plain Fynbos community near
Atlantis and to assess whether or not, the detrimental effect A. saligna has on plant biodiversity,
has reached the stage where it has become irreversible. The floristic data confirmed results from
earlier studies, that invasion of A. saligna in Fynbos communities induces a decline in plant
diversity, especially in dense acacia thickets. This study mainly revealed structural changes rather
than community shifts. The enrichment of the soil as noted by others authors was also confirmed
for the study area. However, it was outside the scope of this study to determine the long-term
effects of this enrichment on the Sand Plain Fynbos communities. Soil moisture content was
sampled on three different occasions, in densely invaded and uninvaded study plots. The aim was
to see if A. saligna had any influence on the availability of water in the upper soil. Contrary to
expectations, moisture content under acacia stands was higher in spring and early summer in the
top soil than in pristine fynbos. Pitfall traps were used to sample the arthropods that dwell the
surface of the study area. For arthropods in general, the survey did not produce conclusive data,
but spider species seem to be positively affected by the presence of A. saligna, probably due to
the structural diversity they add to the fynbos. This study revealed that the full ecological impact
of A. saligna on its environment is far from understood, mainly due to the richness and
complexity of the fynbos communities and a lack of research about faunal aspect of the Fynbos
ecosystem. / AFRIKAANSE OPSOMMING: Die Australiese akasia, A. saligna, is wydverspreid in die Wes-Kaap, Suid-Afrika, en word
dikwels gebruik deur die plaaslike gemeenskap. Dit is dan nie verbasend dat die invoering van die
biologiese bestrydingsmiddel, die swam Uromycladium Tepperianum in 1987, met teenstrydige
emosies ontvang is nie. In 'n poging om die sosio-ekonomiese en ekologiese impak van die swam
te bepaal, het die Department van Waterwese en Bosboukunde 'n ondersoek aangevra waarvan
die tesis deel vorm. Vir die tesis word 'n aantal parameters, omgewings sowel as biologies,
geproef, geanaliseer en vergelyk met bestaande data van vroeër navorsing. Die doel van die studie
is om te bepaal watter effek A. saligna op 'n sandpleinfynbos gemeenskap naby Atlantis het en
om sodoende vas te stelof die nadelige effek van A. saligna op die biodiversiteit onomkeerbaar
is. Plantaardige data bevestig resultate uit vroeër studies dat A. saligna 'n afuame in plant
diversiteit, veral in digte akasiabosse, veroorsaak. In die studie word getoon dat die toename van
A. saligna strukturele veranderings in plaas van gemeenskaplike verskuiwings tot gevolg het. Die
verryking van die grond, deur ander navorsers genoteer, word ook in die studie bevestig. Dit is
egter buite die veld van studie om die lang termyn gevolge van die verryking van die grond op die
sandpleinfynbosgemeenskap te beslis. Op drie verskillende geleenthede word die watergehalte
van die grond getoets onder die akasiabosse en die fynbos. Die doel van die toetse is om vas te
stel hoe A. saligna die beskikbaarheid van water in die boonste grondlaag beïnvloed. In
teenstelling is hoër vogtigheidsvlakke in die boonste grondlaag onder die akasiabosse as onder
die fynbos gevind gedurende lente en vroeë somer. Lokvalle is gebruik om monsters te neem van
die antropodieë woonagtig op die oppervlak van die studiearea. Oor die algemeen is die opname
vir die antropodieë onvoldoende. Dit is egter insiggewend dat die spinnekopspesies voordeel trek
uit die aanwesigheid van A. saligna. Dit is waarskynlik omdat die akasia strukturele diversiteit
aan die fynbos verleen. Die studie onthul dat die volle ekologiese impak van A. saligna op sy
omgewing moeilik verstaanbaar is as gevolg van die diversiteit en kompleksiteit van fynbos
asook 'n gebrek aan navorsing.
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Investigating the most favourable seed establishment methods for restoring sand plain fynbos on old fieldsCowell, Carly Ruth January 2013 (has links)
Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Horticulture
in the Faculty of Applied Sciences
at the Cape Peninsula University of Technology, 2013 / Cape Flats Sand Fynbos (CFSF) is one of the most poorly conserved vegetation types in
the Cape Floral Kingdom, and a large proportion of unconserved land is degraded,
primarily as a result of transformation by agricultural, urban developments and invasion by
alien plants. Fynbos restoration is one of the most important management interventions,
both within the current conservation areas and in any future land remnants acquired for
conservation. Many extant remnants are fragmented and isolated, and if successful
restoration protocols are found, it may be possible to improve the conservation targets for
this critically endangered vegetation type. On old fields, where indigenous soil seed banks
have been lost due to alien plant invasion and anthropogenic action, it is essential to reintroduce
the longer-lived fynbos components that contribute to vegetation structure, in
order to facilitate the progress of the ecosystem on a more natural trajectory.
This research is built on an earlier study of optimal ground-preparation treatments for
restoring Sand Fynbos to old fields. This former study indicated that fossorial mammals
(molerats and gerbils) may occur in dense colonies on old fields and present an obstacle
to successful seedling establishment. The project aims to provide protocols for the
establishment of indigenous seedlings from harvested seed onto old fields, in order to
restore Sand Fynbos vegetation. Different pre-sowing treatments and sowing techniques
were tested on large field plots to determine the most efficient protocol. The objectives of
the research were: a) to investigate optimal pre-sowing treatments of indigenous seed for
restoring degraded Sand Fynbos vegetation in old field sites; b) to investigate optimal
sowing techniques on large field plots for restoring degraded Sand Fynbos vegetation in
old field sites with depleted indigenous seed banks; c) to provide guidelines and
disseminate information on optimal sowing protocols, and their costs, for restoring Sand
Fynbos vegetation in degraded areas and old fields. A further component of the research
was to calculate the costs of all treatments on a per hectare basis in order to assess the
cost-effectiveness of the different options.
Several different seed treatments may potentially increase the germination rate and
promote fynbos restoration. These are scarifying, smoke, smoke water, chemical, light and
temperature pre-sowing treatments. In order to keep the number of treatments (including
their interactions) to a manageable level, only soaking in smoke water extract and seed
coat scarification with course sand and grit were tested. A seed sample of each species
was x-rayed at the Millennium Seed Bank in the United Kingdom, to test for viability in the
seed samples, 52 % of the seed collected were empty, a typical indication of wild
harvested seed. All species were germinated at 10/25 °C and 16/8 hours light/dark
respectively. Scarification had a larger overall germination success, smoke water had very
little effect on CFSF species, it is rather that germination is related to temperatures during
a fire that result in seed coat splitting. It was recommended that further investigation using
more species across the Sand Fynbos vegetation be conducted on pre-germination
effects of heat and scarification.
The study site had been cleared of woody invasive alien vegetation and additional site
preparation included the application of a systemic herbicide to kill undesirable herbaceous
weeds, prescribed fire to clear the site of woody debris and destroy weed seeds, and the
local control of fossorial mammals (gerbils and molerats) by placing raptor perches and
owl nesting boxes around the site. This research found that the use of herbicide shortly
after the prescribed fire and once again prior to sowing was successful in controlling
herbaceous weeds and the indigenous grass Cynodon dactylon. The challenge to using
prescribed burning on old fields was low fuel loads, which resulted in a cool patchy. It is
suggested that cutting and spreading of alien plant biomass is tested as a solution,
however, the material must be evenly spread across the site and not stacked into piles
which can cause excessively hot fires and scorching of the soil. In order to better
understand soil conditions across the site, soil samples were collected prior to sowing, to
analyse for soil macronutrients, organic matter and pH. It was established that all the
excess nutrients added to the site from agriculture and pasturage over the years had
leached from the soil. However, the organic matter content of the soil was extremely low
and research needs to be done on the organic carbon content of the soils, how these
relate to soil micro biota (which species are present and their relationship with CFSF
species) and how best to enrich the site with humic matter for restoration and
establishment of Cape Flats Sand Fynbos. The field trial was set up in the Blaauwberg
Nature Reserve, a random split-plot block design, was replicated five times and used to
investigate the selected seedbed preparation and sowing techniques, namely: broadcast
sowing onto unprepared seedbed, broadcast with plank embedding of seed onto disked
seedbed, broadcast onto disked seedbed and hydro-seed with disked seedbed. Results
from the research found that the most successful methods for sowing seeds were the
hydro-seeding and broadcast with plank embed. These methods may have provided
better contact between the soil and seeds and better protection from predation and wind.
Economically the broadcast and embed was better as machinery was more efficient and
effective than manual labour. This study recommended that these two methods be
combined with the additional planting of rare and threatened species in clumps to
determine the benefits and interactions of each technique over the long term.
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The restoration of an alien-invaded riparian zone in grassy fynbos, South AfricaFourie, Saskia January 2013 (has links)
The most recent surveys in South Africa estimate that invasions are still increasing, despite substantial clearing efforts. Riparian systems in South Africa are particularly vulnerable to invasion by woody IAPs. This thesis addresses the restoration of alien‐invaded riparian systems, by investigating the factors that facilitate or constrain spontaneous recovery and influence the trajectories of succession. These factors include invasion history and management history, especially the use of fire. A seedling emergence approach was used to test the presence of a viable pre‐fire seedbank, and the effect of fire on the seed bank. The efficacy of some active restoration interventions was also tested, with the aim to return invasion‐resistant, indigenous vegetation with a structure and function representative of uninvaded sites. The findings of this study indicated the presence of a viable and persistent riparian soil seed bank, even after 30 years of intermtittent invasion as well as two fire cycles under invasion. It shows that the management practice of fell‐and‐burn resulted in high soil temperatures, and that this reduced the indigenous soil seed bank density, especially in the upper soil layer. Clear germination sequences and patterns of emergence over time for different species were observed during this study, with many species exhibiting delayed emergence relative to the timing of the fire event. It is proposed that manipulation of the season of fire could be used to selectively optimise the order of arrival and therefore superior recruitment of some species over others in the Eastern Cape fynbos, and thus alter the trajectories of recovery of vegetation towards a more desired state. Active restoration in the form of indigenous seed and plant additions resulted in a significantly higher indigenous cover after seven months, compared to a control (passive restoration) or restoring with grass. Indigenous cover and composition was also strongly influenced by lateral zonation, and some key guilds and species were missing or present in much lower densities compared to reference sites. Grass restoration significantly suppressed the regeneration of A. longifolia, as well as the regeneration of indigenous species. Biotic resistance can thus be achieved through restoration, and it could be a powerful tool in the management of IAPs, although the deliberate introduction of grass after clearing in fynbos also reduces biodiversity and could have unforeseen consequences to riparian function.
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Life history, population dynamics and conservation status of Oldenburgia grandis (Asteraceae), an endemic of the Eastern Cape of South AfricaSwart, Carin January 2008 (has links)
Oldenburgia grandis is a rare, long-lived woody paleoendemic of the Fynbos Biome of South Africa. Confined to quartzite outcrops, it has a small geographic range and narrow habitat specificity. O. grandis responds to its fire-prone environment by resprouting. Elasticity analysis of O. grandis reveals that growth and fecundity were traded off for persistence of adult, mature and sapling stages. Morphological adaptations such as a corky fire-resistant bark and the ability to resprout after fire are traits that O. grandis have evolved to persist in a frequently disturbed environment. Population growth rate for sites undisturbed by fire for a number of years (l = 1.01) and sites at various stages of recovery after fire (l = 1.00) were very similar. The highest variation in transition probabilities for all sites was seen in the persistence of the seedling stage and growth from seedling to sapling. Observed population structure and stable stage distribution determined by the matrix model show that sites recently undisturbed by fire had high abundances of the adult and sapling stages. A peak in sapling stages was seen for the stable stage distribution where similar peak in sapling numbers were seen for population structures of sites at various stages of recoveryafter fire. Favourable environmental conditions for the persistence of O. grandis populations include no fire with transition probabilities between the observed minimum and maximum and fire frequency at a 10 year interval where seedling protection from the fire is high and adult and mature mortalities during the fire are low. Stochastic environmental events that could put populations (particularly small populations) at an increased risk of extinction include high to moderate fire intensities where seedling protection from the fire is low and adult and mature mortalities are high as a result of the fire.
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