The alpine flora on inselberg summits in the Maloti–Drakensberg Park, KwaZulu-Natal, South Africa

Robert F Brand,Charles R Scott-Shaw,Timothy G O’Connor

doi:10.4102/abc.v49i1.2386

Abstract

Background: Inselberg summits adjacent to the Maloti–Drakensberg escarpment occupy an alpine zone within the Drakensberg Alpine Centre (DAC). Inselbergs, the escarpment and surrounding mountains such as Platberg experience a severe climate; inselberg summits are distinct by being protected from human disturbance.Objectives: The aim of this article was to describe for the first time the flora of inselberg summits and to assess their potential contribution to conservation of DAC plant diversity.Method: We investigated whether the flora of inselberg summits formed a representative subset of the DAC flora in terms of shared, especially endemic or near endemic, species and representation of families. All species were listed for six inselbergs between Giant’s Castle and Sentinel, located in the Royal Natal National Park (RNNP) during November 2005. Comparisons, using literature, were made with floras of the DAC, as well as Platberg, an inselberg approximately 60 km north from Sentinel in the RNNP.Results: We recorded 200 species of pteridophytes and angiosperms on inselbergs, 114 DAC endemics or near endemics, one possible new species, and several range and altitudinal extensions. Asteraceae, Poaceae and Ericaceae comprised 42.1% of endemic and near endemic species, with Scrophulariaceae and Hyacinthaceae contributing 8.8%. Inselberg and DAC floras differed in respective rankings of Crassulaceae (8th vs. 15th), Polygalaceae, Apiaceae and Rosaceae (10th, 11th, 12th vs. 15th), Poaceae (2nd vs. 5th), Cyperaceae (3rd vs. 4th) and Scrophulariaceae (6th vs. 2nd). Growth forms on inselbergs were consistent with DAC flora. Inselbergs shared 40% of species with Platberg.Conclusion: Inselbergs, which supported 7.9% of species occurring in the DAC flora, are well protected from human impact, lack alien plants, but, despite this, are highly vulnerable to climate change. Conservation importance of inselbergs will increase as escarpment vegetation becomes increasingly degraded as a consequence of intensifying land use.

Highlights

Montane systems across the globe are characterised by pronounced environmental gradients in relation to altitude and in most cases a unique flora adapted to an extreme high altitude environment (Körner 2003)
Inselbergs, which supported 7.9% of species occurring in the Drakensberg Alpine Centre’ (DAC) flora, are well protected from human impact, lack alien plants, but, despite this, are highly vulnerable to climate change
A total of 200 species representing 45 families and 91 genera (Table 1) were recorded in a total area surveyed of 31.9 ha; a complete list of species is provided in Appendix 1

Summary

Introduction

Montane systems across the globe are characterised by pronounced environmental gradients in relation to altitude and in most cases a unique flora adapted to an extreme high altitude environment (Körner 2003). Many montane regions consist of a set of relatively separate peaks, whereas the Drakensberg is structured as a dissected plateau bounded by a steep, tall escarpment on the eastern flank (Partridge 1997). This high altitude plateau has been recognised as a centre of plant endemism and a biodiversity hotspot (Cowling & Hilton-Taylor 1997) known as the ‘Drakensberg Alpine Centre’ (DAC) (Carbutt & Edwards 2004, 2006). Most of the DAC falls within Lesotho a small portion is situated within South Africa east of the national boundary defined by the summit watershed. Inselbergs, the escarpment and surrounding mountains such as Platberg experience a severe climate; inselberg summits are distinct by being protected from human disturbance

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