Plant Ecology

, Volume 142, Issue 1–2, pp 57–69 | Cite as

Community structure on unusual habitat islands: quartz-fields in the Succulent Karoo, South Africa

  • Ute Schmiedel
  • Norbert Jürgens


Quartz fields are edaphically arid, azonal habitats occurring under different macroclimatic conditions in several arid regions of southern Africa. They are the exclusive home of 142 plant species of which ca. 70% are local or regional endemics. This paper is an analysis of the quartz-field floras and growth form-soil relationships in two quartz field regions: the Knersvlakte in the Namaqualand-Namib Domain of the Succulent Karoo, and the western Little Karoo in the Southern Karoo Domain. The Knersvlakte supported 52 quartz-field specialists of which 39 were endemic to the region. Corresponding data for the Little Karoo were 11, and 10 species, respectively. In both regions, the average canopy cover on the quartz-field relevés was ca. 8%, and more than half of this comprised contracted, succulent nanochamaephytes. Cover and vegetation stature were markedly higher on adjacent zonal habitats. Quartz fields in both regions supported a similar array of compact, subglobose and subterranean nanochamaephytes, as evidenced by convergent patterns in two distantly related genera (Argyroderma N. E. Brown and Gibbaeum (Haworth) N. E. Brown, both Mesembryanthemaceae), endemic to the Knersvlakte and largely restricted to the Little Karoo, respectively. Analyses of vegetational and edaphic data of quartz fields and adjacent, zonal habitats were carried out using multivariate direct gradient analysis (Canonical Correspondence Analysis) in order to identify those factors that control the peculiar composition of growth forms on quartz fields. The results revealed highly similar patterns of growth form composition in relation to similar edaphic gradients in both regions. In general, the soils of quartz fields were shallower compared to those of adjacent zonal habitats. In both regions, two different groups of quartz-field edaphic habitats, representing extremes of a continuum, were identified. Group 1 was characterized by high salt content, neutral to slightly acid soil pH, and low stone content. Group 2 was characterized by low salt content, low soil pH, and high stone content. Group 1 quartz fields are the most edaphically arid habitats and support the highest relative cover and diversity of subglobose and subterranean chamaephytes. The combination of reduced competition from larger growth forms, shallow soils and high soil salinity, represents a regionally unusual selective regime. Some succulent lineages in the Mesembryanthemaceae have undergone diversification which has resulted in the fine-scale discrimination of subtle edaphic gradients within the saline quartz-patch habitats. Reliable seasonal rainfall and reduced thermal stress have also played a role in the evolution of quartz patch specialists.

Convergence Desert growth forms Dwarf succulents Gradients Multivariate gradient analysis Winter-rainfall desert 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bittrich, V. & Hartmann, H. 1988. The Aizoaceae-a new approach. Bot. J. Linn. Soc. 97: 239-254.Google Scholar
  2. Cowling, R. M., Esler, K. J., Midgley, G. F. & Honig, M. A. 1994. Plant functional diversity, species diversity and climate in arid and semi-arid southern Africa. J. Arid Env. 27: 141-58.Google Scholar
  3. Cowling, R. M., Esler, K. J. & Rundel, P. W. 1999. Namaqualand, South Africa-an overview of a unique winter-rainfall desert ecosystem. Plant Ecol. 142: 3-21 (this issue).Google Scholar
  4. Cowling, R. M. & Hilton-Taylor, C. In press. Plant biogeography, endemism and diversity. In: Dean, W.R.J. & Milton, S.J. (eds), The Karoo: ecological patterns and processes. Cambridge University Press, Cambridge.Google Scholar
  5. Desmet, P. G. & Cowling, R. M. 1999. Biodiversity, habitat and range-size aspects of a flora from a winter-rainfall desert in north-western Namaqualand, South Africa. Plant Ecol. 142: 23-33 (this issue).Google Scholar
  6. Ellenberg, H. & Mueller-Dombois, D. 1965/66. A key to Raunkiaer plant life forms with revised subdivisions. Ber. geobot. Inst. ETH., Stift. Rübel 37: 56-73.Google Scholar
  7. Eller, B. M. 1982. Strahlungsabsorption von Argyroderma pearsonii (N. E. Br.) Schw. in der Vegetations-und Ruheperiode. Ber. Deutsch. Bot. Ges. 95: 333-340.Google Scholar
  8. Eller, B. M. & Nipkow, A. 1983. Diurnal course of the temperature in a Lithops sp. (Mesembryanthemaceae Fenzl) and its surrounding soil. Plant, Cell Envir. 6: 559-565.Google Scholar
  9. Eller, B. M. & Grobbelaar, N. 1986. Diurnal temperature variation in and around a Lithops lesliei plant growing in its habitat on a clear day. South African J. Bot. 52: 403-407.Google Scholar
  10. Esler, K. J. & Rundel, P. W. 1999. Comparative patterns of phenology and growth form diversity in two winter rainfall deserts: the Succulent Karoo and Mojave Desert ecosystems. Plant Ecol. 142: 97-104 (this issue).Google Scholar
  11. Hammer, S. A. 1993. The genus Conophytum. Succulent Plant Publications, Pretoria.Google Scholar
  12. Hartmann, H. E. K. 1977. Monographie der Gattung Argyroderma N. E. Br. (Mesembryanthemaceae Fenzl). Mitt. Inst. Allg. Bot. Hamburg 15: 121-235.Google Scholar
  13. Hartmann, H. E. K. & Liede, S. 1986. Die Gattung Pleiospilos s. lat. (Mesembryanthemaceae). Bot. Jahrb. Syst. 106: 433-485.Google Scholar
  14. Hartmann, H. E. K: 1991. Mesembryanthema. Contrib. Bol. Herb. 13: 75-157.Google Scholar
  15. Hilton-Taylor, C. 1994. Western Cape Domain. Pp. 204-217. In: Heywood, V. H. & Hamilton, A. C. (eds), Centres of Plant Diversity. Information Press, Oxford.Google Scholar
  16. Hilton-Taylor, C. 1996. Patterns and characteristics of the flora of the Succulent Karoo Biome, southern Africa. Pp 58-72. In: van der Maesen, L. J. E., van der Burgt, X. M. & van Medenbach de Rooy, J. M. (eds), The biodiversity of African plants. Kluwer Academic Publishers, Dordrecht, The Netherlands.Google Scholar
  17. Hoffman M. T. & Cowling R. M. 1987. Plant physiognomy, phenology and demography. Pp. 1-34. In: Cowling, R. M. & Roux, P. W. (eds), The karoo biome: a preliminary synthesis. Part 2-vegetation and history. South African National Scientific Programme Report No. 142, Pretoria.Google Scholar
  18. Ihlenfeldt, H.-D. 1994. Diversification in an arid world: The Mesembryanthemaceae. Ann. Rev. Ecol. Syst. 25: 521-46.Google Scholar
  19. Jongman, R. H. G., ter Braak, C. J. F. & van Tongeren, O. F. R. (eds). 1987. Data analysis in community and landscape ecology. Pudoc, Wageningen.Google Scholar
  20. Jürgens, N. 1986. Untersuchungen zur Ökologie sukkulenter Pflanzen des südlichen Afrika. Mitt. Inst. Allg. Bot. Hamburg 21: 139-365.Google Scholar
  21. Jürgens, N. 1991. A new approach to the Namib Region. I: Phytogeographic subdivision. Vegetatio 97: 21-38.Google Scholar
  22. Midgley, G. F. & van der Heyden, F. in press. Form and function in perennial plants. In: Dean, W. R. J. & Milton, S.J. (eds), The Karoo: ecological patterns and processes. Cambridge University Press, Cambridge.Google Scholar
  23. Milton, S. J., Yeaton, R. I., Dean, W. R. J. & Vlok, J. H. J. 1997. Succulent Kara. Pp. 131-166. In: Cowling, R. M., Richardson, D. M. & Pierce, S. M. (eds), Vegetation of southern Africa. Cambridge University Press, Cambridge.Google Scholar
  24. Nel, G. C. 1953. The Gibbaeum Handbook. Blandford Press, London.Google Scholar
  25. Nobel, P. S., Geller, G. N., Kee, S. C. & Zimmerman, A. D. 1986. Temperatures and thermal tolerances for cacti exposed to high temperatures near the soil surface. Plant, Cell Env. 9: 279-287.Google Scholar
  26. Nobel, P. S. 1989. Shoot temperatures and thermal tolerances for succulent species of Haworthia and Lithops. Plant, Cell Env. 12: 643-651.Google Scholar
  27. Nordenstam, B. 1969. Phytogeography of the genus Euryops (Compositae). Opera Bot. 23: 2-77.Google Scholar
  28. Raunkiaer, C. 1934. Plant life forms. Oxford University Press, Oxford.Google Scholar
  29. Schmiedel, U. 1994. Standortökologische und strukturelle Untersuchungen zur Vegetation der Quarzflächen in der Knersvlakte (Südafrika). Exam. thesis, Univ. of Hamburg.Google Scholar
  30. Smilauer, P. 1992. CanoDraw. Microcomputer Power, Ithaca.Google Scholar
  31. ter Braak, C. J. F. 1986. Canonical correspondence analysis: a new eigenvector method for multivariate direct gradient analysis. Ecology 67: 1167-1176.Google Scholar
  32. Turner, J. S. & Picker, M. D. 1993. Thermal ecology of an embedded dwarf succulent from southern Africa (Lithops spp.: Mesembryanthemaceae). J. Arid Env. 24: 361-385.Google Scholar
  33. Van Jaarsveld, E. 1987 The succulent riches of South Africa and Namibia. Aloe 24: 45-92.Google Scholar
  34. von Willert, D. J., Eller, B. M., Werger, M. A., Brinckmann, E. & Ihlenfeldt, H.-D. 1992. Life strategies of succulents in deserts. With special reference to the Namib desert. Cambridge University Press, Cambridge.Google Scholar
  35. Weather Bureau 1988. Climate of South Africa. Climate Statistics up to 1984. Department of Environment Affairs. Pretoria.Google Scholar
  36. Werger, M. J. A. 1978. The Karoo-Namib Region. Pp. 231-299. In: Werger, M. J. A. (ed), Biogeography and ecology of southern Africa. Junk, The Hague.Google Scholar

Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Ute Schmiedel
  • Norbert Jürgens

There are no affiliations available

Personalised recommendations