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  • 1
    Monograph available for loan
    Monograph available for loan
    Namaqualand : a succulent desert (1999)
    Vlaeberg : Fernwood Press
    Details Availability
    Call number: PIK N 630-15-89519
    Type of Medium: Monograph available for loan
    Pages: 156 S. , Ill. , 31 cm
    ISBN: 1874950415 (standard ed.) , 1874950423 (collector's ed.)
    Language: English
    Location: A 18 - must be ordered
    Branch Library: PIK Library
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of Restoration Techniques for the Succulent Karoo, South Africa (2003)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 11 (2003), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Possible constraints on the passive recovery of bare areas in the Karoo, a semiarid region in South Africa, include inadequate supply of seed, availability of suitable microsites for plant establishment, altered soil properties, and the truncation of key soil biotic processes. Here we investigate the possibility of initiating the restoration of bare areas by soil surface treatments with gypsum (CaSO4) and/or organic mulch. We also apply an exogenous seed source to test the hypothesis that seed availability limits autogenic recovery. Both gypsum and mulch improved rain water infiltration, gypsum more so than mulch, and both treatments resulted in significantly higher numbers of reseeded seedlings compared with controls. Gypsum also improved the survival of the cohorts of seedlings of the larger seeded Tripteris sinuata. Tripteris showed the highest number of seedlings (maximum count of 150 seedlings/1,000 viable seeds sown) and surviving plants of the three reseeded species, which included two small-seeded species, Ruschia spinosa and Chaetobromus dregeanus. Throughout the study period significantly higher plant volumes of naturally seeded annuals and perennials were recorded in the gypsum and/or mulch treatments compared with the controls. Germination and emergence of reseeded and naturally seeded plants appears to be determined by the availability of cool season (autumn to spring ) soil moisture, whereas follow-up rainfall during this time is important for plant survival. Mulching of bare areas in the Succulent Karoo has the potential to re-create vegetated areas that will further capture and conserve water, soil, and nutrients. Gypsum also showed positive results but might not be a cost-effective option because of transport costs to these remote arid areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.2003.00192.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of goat pastoralism on ecosystem carbon storage in semiarid thicket, Eastern Cape, South Africa (2005)
    Melbourne, Australia : Blackwell Science Pty
    Austral ecology 30 (2005), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Intensive pastoralism with goats transforms semiarid thicket in the Eastern Cape, South Africa from a dense vegetation of tall shrubs to an open landscape dominated by ephemeral grasses and forbs. Approx. 800 000 ha of thicket (which prior to the introduction of goats had a closed canopy and a Portulacaria afra Jacq. component) have been transformed in this manner. Ecosystem C storage in intact thicket and loss of C due to transformation were quantified. Carbon storage in intact thicket was surprisingly high for a semiarid region, with an average of 76 t C ha−1 in living biomass and surface litter and 133 t C ha−1 in soils to a depth of 30 cm. Exceptional C accumulation in thicket may be a result of P. afra dominance. This succulent shrub switches between C3 and CAM photosynthesis, produces large quantities of leaf litter (approx. 450 g m−2 year−1) and shades the soil densely. Transformed thicket had approx. 35% less soil C to a depth of 10 cm and approx. 75% less biomass C than intact thicket. Restoration of transformed thicket landscapes could consequently recoup more than 80 t C ha−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1442-9993.2005.01523.x
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  • 4
    Electronic Resource
    Electronic Resource
    The occurrence of C3 and C4 grasses in fynbos and allied shrublands in the South Eastern Cape, South Africa (1983)
    Springer
    Oecologia 58 (1983), S. 121-127 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary There are roughly equal numbers of C3 and C4 grass species in fynbos and allied shrublands of the warm temperate coastal regions of the south eastern Cape. Subtropical-tropical C4 species have the highest relative cover in all shrubland types, particularly in renosterveld communities on moderately fertile soils. Physiological characteristics of C3 and C4 grasses predict that C3 species will be most abundant in cool, shaded sites. This prediction, and the hypothesis that relative C3 grass cover would be highest on infertile soils, were tested by correlation and regression analyses. Results show that C3 grass cover is significantly correlated with increased post-disturbance vegetation age, low intensity grazing, high litter cover and cool, steep, poleward slopes. All these factors contribute to lower growing season temperatures, favouring the competitive growth of C3 species. Amongst the soil variables, high sand content and low levels of total nitrogen emerged as predictors of high relative C3 grass cover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384551
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  • 5
    Electronic Resource
    Electronic Resource
    Winter growth phenology and leaf orientation in Pachypodium namaquanum (Apocynaceae) in the succulent karoo of the Richtersveld, South Africa (1995)
    Springer
    Oecologia 101 (1995), S. 472-477 
    Details
    ISSN: 1432-1939
    Keywords: Pachypodium namaquanum ; Orientation ; Succulent karoo ; Richtersveld ; Energy balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pachypodium namaquanum (Nyley ex Harb.) Welw., an unusual arborescent stem succulent from the succulent karoo of the arid Richtersveld in north-western South Africa and adjacent Namibia, is characterized by a striking curvature of the terminal 20–60 cm of the trunk toward the north. This orientation displays the single terminal whorl of drought-deciduous leaves with their flat surface angled at a mean inclination of 55° from horizontal. Inclination of 50–60° was found in 65% of individuals sampled, and 85% were inclined between 45 and 65°. Northward azimuth was also quite regular, but varied slightly between populations. The fixed leaf orientation in P. namaquanum maximizes radiation absorption during the winter months when leaves are present. Leaves normally form in early fall (April) and abscise early in spring (October). Growing season conditions in the Richtersveld are relatively mild, with mean maximum temperature dropping only to 21.6°C in July, the coldest month of the year. Frosts are rare. By the fixed orientation of its leaf whorl, P. namaquanum is able to maintain nearly twice the midwinter radiation absorptance that it would have with horizontal orientation. Over an annual cycle the angled leaves receive more radiation than would horizontal leaves for each of the 6 months in which they are present on the plant. This increased winter irradiance is hypothesized to singificantly increase net primary production by concentrating growth activities in winter months and allowing the species to remain dormant during the hyperarid conditions of the hot summer months. Midwinter flowering from apical buds in P. namaquanum may also be aided by its stem orientation. The evolution of this characteristic pattern of winter growth phenology and nodding stem orientation may have come about because of low but relatively regular autumn precipitation and moderate winter temperatures. Slow and regular growth of P. namaquanum leads to long lifespans which may reach 300 years or more.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329426
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  • 6
    Electronic Resource
    Electronic Resource
    Smoke-induced germination of succulents (Mesembryanthemaceae) from fire-prone and fire-free habitats in South Africa (1995)
    Springer
    Oecologia 102 (1995), S. 520-522 
    Details
    ISSN: 1432-1939
    Keywords: Seed ; Germination ; Fire ; Mesembryanthemaceae ; Smoke
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have shown germination to be stimulated by fire-related cues such as heat and charate extract and, more recently, plant-derived smoke extract. However, smoke extract has not been tested on non-fire-prone species. We hypothesized that smoke-induced germination would be restricted to fire-prone species and investigated responses of members of the family Mesembryanthemaceae which has genera confined to fire-prone and to non-fire-prone habitats as well as genera with species across both habitats. Results of germination trials of smoke effects did not support the hypothesis. Plant-derived smoke extract stimulated germination in both fire-prone and non-fire-prone species. These results cast some doubt on the ecological significance of smoke as a fire-related cue and we suggest that investigation of effects of fire-related cues on non-fire prone species may throw light on general mechanisms of germination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341366
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  • 7
    Electronic Resource
    Electronic Resource
    Seed size: phylogeny and adaptation in two closely related Proteaceae species-pairs (1992)
    Springer
    Oecologia 91 (1992), S. 292-295 
    Details
    ISSN: 1432-1939
    Keywords: Seed size ; Soil nutrient and water status ; Phylogenetic constraints ; Relative growth rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied seed size, seed nutrient status and seedling growth of two closely related fynbos Proteaceae species-pairs growing on juxtaposed soils of different nutrient and moisture status. Seeds had a greater mass and higher phosphorus and nitrogen contents for species occurring on limestone (higher nutrient and moisture contents) than those on the colluvial sands (lower nutreints and moisture). This trend was found within, but not across genera, stressing the importance of phylogeny in interpreting adaptations. It would be difficult to test for the effects of either nutrients or moisture separately, since the same advantage of enhanced seedling size, and hence survival in a stressed environment, applies to both factors. The increased root: shoot ratios (using lengths) of the Leucadendron species relative to the Protea species are interpreted as an attempt to overcome a phylogenetic constraint that results in smaller seed size in the former genus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317799
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  • 8
    Electronic Resource
    Electronic Resource
    Modelling the biological aspects of local endemism in South African Fynbos (1995)
    Springer
    Plant systematics and evolution 195 (1995), S. 137-147 
    Details
    ISSN: 1615-6110
    Keywords: Fynbos ; endemism ; dispersal ; growth form ; regeneration ; logistic regression analysis ; model ; Flora of the Cape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The biological attributes, dispersal mode, growth form, and regeneration strategy were determined for the endemic and non-endemic flora of the southern Langeberg, Cape Province, South Africa.—Logistic regression analysis was used to assess the simultaneous effects and interactions between these biological attributes on the occurrence of endemism. The model allowed numerical estimation of the probability that a species with a given set of attributes would be endemic.—This approach extends a contingency table analysis of the data, which merely indicated the association between individual biological traits and endemism. Furthermore, the logistic model allows scope for the analysis of the influence of biological traits in determining endemism in other floras, and also tentative prediction of the probability of endemism in species with combinations of biological traits not yet observed in the flora of the southern Langeberg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00989290
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  • 9
    Electronic Resource
    Electronic Resource
    Vegetation-environment relationships on a species-rich coastal mountain range in the fynbos biome (South Africa) (1996)
    Springer
    Plant ecology 123 (1996), S. 165-182 
    Details
    ISSN: 1573-5052
    Keywords: Classification ; Fynbos ; Gradient analysis ; Vegetation-environment relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The species-rich fynbos of the southern Langeberg Mountains, South Africa was studied along three transects (a) to evaluate the compatibility of a floristic classification of the southern Langeberg vegetation with a fynbos biome-wide structural classification of mountain vegetation, (b) to describe the environmental gradients to which the vegetation responds and (c) to investigate the relationship between the vegetation and the abiotic environmental variables which determine the pattern of distribution of the fynbos communities on the southern Langeberg. Principal Components Analysis (PCA) was used to determine correlations between environmental variables independent of vegetation data. Similarities between the 46 communities (determined by floristics) from the three transects were determined using cluster analysis and grouped into 14 higher-level units. Detrended Correspondence Analysis (DCA) was then used for indirect gradient analysis after which Canonical Correspondence Analysis (CCA) was used in a direct gradient analysis of the vegetation with the environmental variables. Compatibility between the floristic and structural classification of the vegetation was analysed. The PCA principal gradient was defined as one from sites with high rock cover, shallow soils and north aspects to those with low rock cover, deeper soils and south aspects. The second gradient is most strongly positively correlated with percentage organic carbon and most strongly negatively correlated with soil clay content. In contrast to the PCA, the DCA showed that the principal gradient is a precipitation gradient, with the response of the vegetation dominated by the change from wet to dry conditions and from low to high winter incoming radiation. The CCA showed that the variation in the mountain habitats to which the vegetation responds can be predicted from a combination of a few environmental variables. The principal gradient was one of change from high to low mean annual precipitation with an opposite change in winter incoming radiation. The second gradient was described by percentage surface rock cover and soil clay content. A simple model using the environmental factors selected in the CCA was proposed for predicting the distribution of floristically determined community groups in the fynbos vegetation of the Langeberg and the southern Cape coastal mountains in general.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118269
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  • 10
    Electronic Resource
    Electronic Resource
    Soil nutrient dynamics and community boundaries in the Fynbos vegetation of South Africa (1997)
    Springer
    Plant ecology 130 (1997), S. 143-153 
    Details
    ISSN: 1573-5052
    Keywords: Community boundaries ; Fynbos ; Nitrogen ; Phosphorus ; Soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between changes in soil nutrient characteristics and fynbos community boundaries was investigated near Cape Agulhas, South Africa. Soil characteristics relating to total nutrient content (pH, total N and total P, organic carbon, and various cations) were assessed at sites along three transects crossing the boundaries between five plant communities. Dynamics of available N and P in soils of three communities were studied in the field over one year, using ion-exchange resins. There was a wide range in the degree of change in soil nutrient content across different community boundaries. The characteristics that varied most were pH, total N, Ca and total P. Differences in available nutrients among soils indicated that the communities in this landscape were associated with a mosaic of N and P availability. It is proposed that spatial variation in soil nutrient availability rather than total soil nutrient contents may be important in explaining landscape-level species distributions and community composition in nutrient-poor mediterranean-climate ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009742225383
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