Sandstone Fynbos Research Articles

Passerina ternata (Thymelaeaceae): A new species from the Baviaanskloof, South Africa

• Passerina ternata Magee & D.I.W. Euston-Brown is formally described. • New species a resprouting shrub, with leaves distinctly ternate. • 21 species of Passerina now recognised. • Taxonomic key of Bredenkamp and Van Wyk (2003) revised. Passerina ternata Magee & D.I.W.Euston-Brown is described as a new species from the Baviaanskloof mountains, Eastern Cape Province of South Africa. The species is currently known from a single population within Kouga Sandstone Fynbos. It is a multi-stemmed resprouting shrub to 1.5 m, with linear leaves arranged in whorls of three, the leaves and bracts sticky, yellowish-green flowers with green anthers, and apically falcate bracts with the inner surface densely villous in the lower three-quarters and shortly setose in the upper quarter. Passerina falcifolia has similar apically falcate bracts but entirely villous on the inner surfaces . Passerina falcifolia differs further in that it is large shrub to 3 m, with lax, flaccid willowy lateral flowering branches, the opposite leaves are spreading and usually strongly falcate and the anthers are cream. The addition of Passerina ternata brings the number of species currently recognised within Passerina L. to 21 and the taxonomic key of Bredenkamp and Van Wyk (2003) is revised to accommodate the new species.

A new species of Cyrtanthus (Amaryllidaceae: Cyrtantheae) from the Agulhas Plain, Western Cape, South Africa

Described is a new species of Cyrtanthus within the monogeneric tribe Cyrtantheae (Amaryllidaceae: Amaryllidoideae) from the low-lying Agulhas Plain, Western Cape, South Africa. Known from the Nuwejaars Wetlands area, Cyrtanthus novus-annus occupies habitats transitional between Elim Ferricrete Fynbos and Central Rûens Shale Renosterveld. The erect, mostly solitary-flowered inflorescence has a nearly sessile, funnel-shaped flower in common with C. guthrieae, which occurs on the mountains close to Bredasdorp in acidic soils of Overberg Sandstone Fynbos. The two species differ in the size, colouring, and markings of the flowers and in their flowering times. Their morphological similarity and the close proximity of their habitats suggest that C. novus-annus and C. guthrieae constitute an example of edaphically differentiated sister taxa, a pattern found in several other endemics of the region, as well as in the sister pair Brunsvigia elandsmontana and B. marginata (tribe Amaryllideae) from contrasting habitats in Swartland lowland alluvium and the abutting sandstone mountains, respectively.

Responses of Watsonia fourcadei and other geophytes to burning and slashing treatments in South Outeniqua Sandstone Fynbos

The often mass flowering of Watsonia and other geophyte species in the first year after a fire in the South African fynbos vegetation is well known, but it has rarely been quantified. Many fynbos geophytes also flower after the fynbos canopy was physically removed, but these flowering responses have also not been quantified. A study comparing the flowering response of geophytes after physical removal versus fire removal of the fynbos canopy was conducted to establish to what degree these species are fire dependant. It was also done to improve our understanding of fynbos geophyte ecology, especially towards establishing if the flowering response of these plants is due to fire related factors per se, or not.Vegetative growth, flowering response, seed set and seedling establishment of Watsonia fourcadei were recorded after two treatments, burning and physical removal of vegetation (slashing) in two veld ages (5- and 16 years). Responses of other co-occurring geophytic species to these treatments were also recorded. The number of vegetatively active W. fourcadei plants doubled and flowering percentage increased from 2.3% to 38.7% in the first year after the fire. In the second year after the fire the number of vegetatively active W. fourcadei plants was similar to those in the first year after the fire, but flowering percentage decreased to pre-fire levels. About 50% of W. fourcadei plants were dormant 5 years after the fire and > 90% were dormant in 16-year old fynbos. Flowering percentages of W. fourcadei in slashed 5-year old fynbos did not differ significantly from burned 16-year old fynbos. The flowering stimulus of W. fourcadei was thus not due to fire associated factors per se. Seed predation of W. fourcadei seed capsules decreased from 46.9% before the fire to 7.1% after the fire. Number of viable seed released increased from 15.8 seed mˉ² pre-fire to 1170.5 seed mˉ² post-fire and 233.1 seedlings mˉ² established after the fire. The 74-fold increase in seed release in the burned fynbos could not be ascribed to higher cross pollination success as about 40% of the flowers were autogamous. The number of vegetatively active geophytic species increased from 2.3 species mˉ² pre-fire to 7.9 species mˉ² post-fire in 16-year old burned fynbos and 4.0 species mˉ² in the slashed fynbos. Most (76%) of these geophytic species flowered after the fynbos was burned and 24% of the species flowered in the slashed fynbos. Only some of the geophytic species were thus dependent on fire to stimulate flowering. A repeated short cycle disturbance regime (ca. 5 years) of burning and/or slashing may result in a super-abundance of Watsonia plants that can displace smaller geophytic species. Previous hypotheses on proximate reasons for the Watsonia post-fire flowering that are rejected are: (i) greater visibility of the plants; (ii) heating of the soil and corms by fire and; (iii) increased availability of phosphorous and/or other minerals in the post-fire environment. Smoke as a factor to induce flowering in W. fourcadei growing under natural conditions is questioned.

Describing a drowned Pleistocene ecosystem: Last Glacial Maximum vegetation reconstruction of the Palaeo-Agulhas Plain

Pleistocene ecosystems provided the stage for modern human emergence. Terrestrial vegetation communities structure resources for human foragers, providing plant food, wood for fuel and tools, and fibre, as well as habitat for animal prey. The Pleistocene distribution of vegetation communities is seldom considered as a key constraint on hunter-gatherers foraging across the landscape. We used modern vegetation patterns along the Cape south coast to develop a rule-based model of the expected vegetation for a given soil type, precipitation regime and fire regime. We then applied this ruleset to present-day environmental conditions to test and validate the model. We also scaled the climate-vegetation ruleset to account for likely effects of low atmospheric [CO2] and lower temperature in the Last Glacial Maximum (LGM) on plant water use efficiency. The model was then used to postdict vegetation patterns for the LGM using palaeo-landscape reconstruction of geological substrata and soils, and palaeoclimate simulations. This palaeoscape comprised the extensive Palaeo-Agulhas Plain (PAP), which was exposed at lower sea levels during glacial periods. Our model predicts that the PAP was dominated by limestone fynbos in its southern part, and by shale grassland with cappings of dune fynbos-thicket mosaic in the north. Shale and sandstone fynbos were restricted to the western zone, which experienced a stronger winter rainfall regime during the LGM than at present. The entire PAP was dissected by broad and shallow floodplains supporting a mosaic of woodland and grassland on fertile, alluvial soils. This savanna-like vegetation, as well as shale grassland, are poorly represented in the modern landscape, and would have been capable of supporting the diverse megafauna typical of glacial periods. These Pleistocene periods would have presented a very different resource landscape for early modern human hunter-gatherers than the interglacial landscape such as is found in the Cape coastal lowlands today.

Firewalls in bee nests-survival value of propolis walls of wild Cape honeybee (Apis mellifera capensis).

The Cape bee is endemic to the winter rainfall region of South Africa where fires are an integral part of the ecology of the fynbos (heathland) vegetation. Of the 37 wild nests in pristine Peninsula Sandstone Fynbos in the Cape Point section of Table Mountain National Park that have been analyzed so far, only 22 could be accessed sufficiently to determine the existence of a propolis wall of which 68% had propolis walls which entirely enclosed their openings. The analysis of the 37 wild nests revealed that 78% occurred under boulders or in clefts within rocks, 11% in the ground, 8% in tree cavities, and 3% within shrubs. The analysis of 17 of these nests following a fire within the park revealed that the propolis walls materially protected the nests and retarded the fire with all the colonies surviving. The bees responded to the smoke by imbibing honey and retreating to the furthest recess of their nest cavity. The bees were required to utilize this honey for about 3weeks after which fire-loving plants appeared and began flowering. Considerable resources were utilized in the construction of the propolis walls, which ranged in thickness from 1.5 to 40mm (mean 5mm). Its physical environment determines the nesting behavior of the Cape bee. The prolific use of propolis serves to insulate the nest from extremes of temperature and humidity, restricts entry, camouflages the nest, and acts as an effective fire barrier protecting nests established mostly under rocks in vegetation subjected to periodic fires.

The use of fynbos fragments by birds: Stepping-stone habitats and resource refugia

Fynbos habitats are threatened by fragmentation through land use and anthropogenic changes in fire regimes, leading to a loss of suitable habitat for birds. We investigated the response of fynbos-typical avifauna to fragmentation and postfire vegetation age in order to better understand the consequences of these processes for bird communities. Vegetation composition and bird inventory data were collected along wandering transects in three South Outeniqua Sandstone Fynbos habitat configurations: fragmented patches (associated with anthropogenically driven habitat loss < 150 years ago), naturally isolated fynbos islands (formed through climate-driven forest expansion in the Holocene) and extensive areas of relatively pristine habitat known as ‘mainland’. The latter configurations served as references against which to investigate bird and vegetation responses to more recent habitat fragmentation. Linear regressions were used to compare the relationships of a number of bird and plant species to areas between each habitat configuration. Bird attribute frequency data were compared between habitat configurations using chi-square tests. Birds and plants showed significant species–area relationships in natural island and mainland sites, but no such relationship occurred in artificial fragments for birds, where the surrounding anthropogenic land uses are likely to have contributed generalist or colonist species. Avifaunal migratory groups were not affected by isolation distances of > 10 km in this study and their frequencies were the same across the three habitat configurations. Certain feeding guilds did, however, respond to postfire vegetation age, with nectarivore species twice as likely to occur in oldgrowth mainland fynbos. Fragmentation can alter fire disturbance regimes, which in turn alter the availability of resources in a habitat, so the impacts of fragmentation on birds are probably indirect through changes in the vegetation component.Conservation implications: Fragments of South Outeniqua Sandstone Fynbos have value as resource refugia and ‘stepping-stone’ reserves for avifauna. Fragments should be managed for vegetation age to ensure that at least some patches sustain high levels of nectarproducing plant species. Fire management should, however, factor in both plant and bird requirements.Keywords: Avifauna; Agricultural Mosaic; Cape Floristic Region; Conservation; Habitat Fragmentation; Species-Area Relationships

A one-year post-fire record of macronutrient cycling in a mountain sandstone fynbos ecosystem, South Africa

Nutrient inputs and dynamics of the fynbos ecosystem, particularly after a fire, are poorly understood. This article provides chemical analyses of macronutrients (Cl, Na, SO4, Mg, Ca and K) in rainwater, stream water, soil and bedrock over a period of one year following a fire event in a coastal mountain sandstone fynbos ecosystem.Rainwater, stream water, soil and bedrock samples were taken from a mountain fynbos area underlain by homogeneous Peninsula Formation sandstone bedrock for a one-year period. Rainwater, stream water and soil saturated paste extracts were analysed for macronutrients using a Dionex DX-120 Ion Chromatograph. Crushed soil and bedrock samples were analysed for major element oxide and S content.Above-ground biomass recovery after one year was modest (5–10% of the 19-year-old pre-fire biomass) with marine aerosols supplying Cl and Na ions to the ecosystem and a significant amount of Mg, SO4, Ca and K. Additional Mg, SO4, Ca and K are supplied by deposition of local and regional fire ash and dust (mineral aerosols) transported from inland sources mostly by northwesterly winter winds. Nutrient loss diminishes rapidly with the return of pre-fire stream values within 9months after fire, with nutrients gradually replaced through atmospheric deposition rather than the slow weathering bedrock.Macronutrients supplied to the study area reflect seasonal differences with atmospheric processes being the primary source of nutrients to the ecosystem.

Measurement and modelling of evapotranspiration in three fynbos vegetation types

Many studies have investigated the water relations of indigenous plants in the fynbos shrublands of the Cape, South Africa. These have mainly focused on understanding the mechanisms by which individual plant species respond to droughts, the frequency and severity of which is expected to increase due to climate change. However, comparatively little information exists on the dynamics of water use by indigenous plants in the region, and, in particular, how water use varies seasonally and between sites. In this study we determined water use by 3 fynbos vegetation types growing at 4 different sites, namely: (i) lowland Atlantis Sand Plain fynbos growing on deep sandy soils, (ii) Kogelberg Sandstone fynbos growing in a riparian zone on deep alluvial soils, (iii) dryland Kogelberg Sandstone fynbos growing on shallow sandy soils at a montane site, and (iv) alluvial Swartland fynbos growing in clayey soils. Evapotranspiration (ET) was quantified at each site during specific periods using a boundary layer scintillometer and energy balance system. A simple dual source model in which the stand ET was calculated as the algebraic sum of outputs from soil evaporation and transpiration sub-models was used to scale up the ET measurements to annual values. The data showed large differences in ET depending on site characteristics and on plant attributes. Dense stands of riparian Sandstone Fynbos had an annual ET of 1 460 mm which exceeded the reference ET of 1 346 mm. Dryland Sandstone Fynbos used only 551 mm of water per year while the Sand Plain Fynbos’ annual ET was 1 031 mm, which was similar to the reference ET of 1 059 mm. We conclude that some indigenous plant species use large volumes of water which should be accounted for in, e.g., groundwater recharge estimates, and calculations of incremental water gains after clearing alien invasive plants, among other applications. Keywords : Evapotranspiration, fynbos, scintillometer, Western Cape

Early post-fire plant succession in Peninsula Sandstone Fynbos: The first three years after disturbance

The early post-fire plant succession in fynbos vegetation in the Mediterranean-type climate area of South Africa was studied. Relatively little has been published on this early stage of plant succession in fynbos. Annual sampling over the first three post-fire years confirmed a steady, but relatively slow increase in plant canopy cover of shrubs and graminoids (mainly Restionaceae), whereas cover of geophytes and other herbs peaked in the first year and declined significantly, thereafter. Cover of annual plants increased each year, which may relate to the persistence of a relatively open vegetation cover by the third year. The responses of reseeder and resprouter species of the Restionaceae to the post-fire environment appeared to be habitat dependent. Cover of the reseeders increased rapidly in seep areas, but their recovery was distinctly delayed in dryland areas outside the seeps. Re-establishment of the many reseeder Erica species appeared to be delayed until the second post-fire year. Seed banks of these species were possibly negatively impacted by the fire, and required dispersal of seed from unburnt areas for recruitment. In contrast to some current generalisations, species richness appeared to increase after the fire; less certainly from the first to the second year, but more certainly from the second to the third year. Therefore, this study does not support a short-term monotonic decline in species richness after fire in fynbos.

Strontium isotope analyses of large herbivore habitat use in the Cape Fynbos region of South Africa

The Cape Fynbos region of South Africa, a global biodiversity hotspot, hosted a diverse large mammal fauna till shortly after permanent European settlement (1652). How these animals survived in this exceptionally nutrient-poor environment is puzzling and it is generally believed that they restricted their movements to the more fertile shale areas. We tested the hypothesis that large herbivores avoid nutrient-poor limestone and sandstone fynbos shrublands in favour of shale-derived renosterveld vegetation using strontium (Sr) isotope analysis. If this technique could reconstruct the preferred feeding habitats of the contemporary fauna, it might also be useful for reconstructing the preferred feeding grounds of an extinct fauna. Using the assumption that small rodents have spatially restricted foraging activities, we determined the (87)Sr/(86)Sr isotope ratios of rodent teeth to establish the isotopic signal characteristic of the different geological substrates in the area. We then analysed (87)Sr/(86)Sr isotope ratios in the bones of a number of different large herbivores found in De Hoop Nature Reserve using laser ablation multi-collector inductively coupled plasma mass spectrometry. These values were compared to the bioavailable (rodent) values on the respective geological substrates. The technique identified differences in feeding substrate selection between different species and groups of the same species. The results also showed that shale renosterveld shrubland is not the exclusive source of nutrition for the large herbivores. Strikingly different isotope ratios among individuals in some populations pointed to significant dispersal events from distant sources. However, we were unable to pinpoint the exact feeding areas using Sr isotope analysis probably because some animals use a combination of substrates for feeding and because the geology of the study area is complex with graded isotope signals. We suggest that this technique is a valuable additional tool for exploring large mammal foraging behaviour on habitats associated with contrasting and less complex geology.

Impacts of ploughing and introduction of commercial fynbos species on the diversity of sandstone fynbos on the Agulhas Plain, South Africa

Impacts of ploughing and introduction of commercial fynbos species on the diversity of sandstone fynbos on the Agulhas Plain, South Africa

The effect of ploughing and augmenting natural vegetation with commercial fynbos species on the biodiversity of Overberg Sandstone fynbos on the Agulhas Plain, South Africa

In an attempt to reconcile wildflower cultivation with plant diversity conservation, we investigate the effect that different augmentation techniques (including ploughing and burning) have on the plant diversity of the Fynbos Biome. We evaluated the effects of two ploughing intensities followed by augmentation at one site, and augmentation without ploughing at another on the plant diversity in Overberg Sandstone fynbos on the Agulhas Plain, South Africa. Results showed that plant diversity was the highest in areas which were either shallow-ploughed and augmented or augmented only; thus these treatments appear not to have a significant negative effect on plant diversity at least in the short-term. Deep ploughing, however, was detrimental to plant diversity. Results could be explained by the intermediate disturbance hypothesis i.e. intermediate levels of disturbance prevent the competitive exclusion of subdominant species. The conclusion drawn from this study is that low-intensity cultivation of commercial fynbos species can be diversity-friendly, but high-intensity disturbance practices should be avoided.

Effects of alien plant management and fire on soil seed banks and regeneration in the Cape Peninsula National Park, South Africa

The regeneration of alien and indigenous vegetation in various post-fire environments, following the extensive January 2000 wildfires on the Cape Peninsula, South Africa, is described. The effects of dry season wildfire burning of standing alien plants and stacks of mechanically cleared, alien plant material, on post-fire seed banks and vegetation recovery, are presented. These are compared to the effects of wildfire burning on adjacent stands of un-invaded Sandstone Fynbos (previously known as Mountain Fynbos) vegetation and to that on cleared areas surrounding wildfire burnt stacks. The effects of stacking and controlled burning of slash of cleared alien plant material on regeneration potential, under cool weather conditions, are also reported. Seed banks and regeneration were linked to pre-fire vegetation characteristics, fire intensity and, in particular, to the management of alien plants. Large volumes of either standing or stacked alien woody plant biomass impact negatively upon post-wildfire seed banks and upon the recruitment of indigenous fynbos vegetation. Heat damage, associated with stacks of woody alien biomass, kills all seeds to a soil depth of at least 0.15m. In contrast, the controlled winter burning of stacks of alien material results in large scale localised germination of alien seeds. Both persistent indigenous seed banks and the seed of alien invasive species are present in the burnt disturbed areas surrounding stacks of alien slash burnt in wildfires. It is concluded that the current practice of stacking slash resulting from the control of alien plants requires urgent review.