Vegetation survey of the Khomas Hochland in central-western Namibia: syntaxonomical descriptions

Abstract

Background: The Great Escarpment of southern Africa takes the form of an extended mountainous highland in central-western Namibia, commonly referred to as the ‘Khomas Hochland’. It is regarded as an area of high botanical diversity. Yet only few localised studies on the vegetation composition are available. The Khomas Hochland is formed on the southern part of the Damara Orogen and dominated by metamorphosed sediments. Climatically it forms a transition between the hot desert of the Namib and the slightly cooler hot steppe in the inland.Objectives: To classify and provide syntaxonomical descriptions of the vegetation of the Khomas Hochland.Methods: A dataset comprising 1151 relevés and 914 species was compiled from various surveys, mostly collected under, and to the standards of, the umbrella project ‘Vegetation Survey of Namibia’. For first classifications, the data set was reduced to a synusial set consisting of trees, shrubs, dwarf shrubs and grasses only.Results: The classification resulted in four major landscape units, being the Pre-Namib and Escarpment zone, the Khomas Hochland proper, riverine habitats as well as surrounding lowlands. The classification was further refined using Cocktail procedures to produce 30 associations, one with four sub-associations. These are described in this paper.Conclusion: A classification of synoptic data grouped the associations into five orders and one undefined cluster of associations on specialised desert habitats. Four of these orders correspond to the habitat types identified in the first classification. The fifth order, the Senegalio hereroensis–Tarchonanthoetalia camphorathi, represents high mountains of the central Khomas Hochland, which link biogeographically to the grassland biome in South Africa.

The mountain top flora and vegetation of the remote Ovahimba Highlands in the Kaokoveld Centre of Endemism: a reconnaissance

“…It is also higher than found for the Brandberg, with 27 species per 1000 m 2 (Jürgens et al, 2013). Species richness was similar to that of the vegetation found in the Khomas Highland proper, an eastern extension of the escarpment towards Windhoek (Strohbach, 2021).…”

“…Typical highland species encountered that are also found at the Brandberg and the Khomas Highland were Dombeya rotundifolia, Ozoroa crassinervia, and Olea europaea subsp. cuspidata (Strohbach, 2021;Craven and Craven, n.d.).…”

“…All vascular plant species in the nine plots, herbaceous and woody, were recorded and their abundance was estimated as projected cover (%), without the use of a scale (Strohbach and Kangombe, 2012;Revermann et al, 2017;Jürgens et al, 2018). Species that only occurred beyond the 17.84 m radius of the sample plot were recorded to allow determining species richness for the commonly used plot size of 1000 m 2 (Jürgens et al, 2013;Strohbach, 2021) facilitating comparisons with other areas. The species were grouped according to life form using four main categories: tree, shrub, herb, and grass.…”

Potential distribution of major plant units under climate change scenarios along an aridity gradient in Namibia

“…The Khomas Hochland forms part of the escarpment and ranges between 1,600 to well over 1,800 m a.s.l. It is a rolling to steep mountainous highland overlaid by lithic Leptosols that are generally shallow and often covered by quarz pebbles (Joubert et al 2008;Strohbach 2017). The Nama-Karoo forms part of the Central Plateau, however with a distinctly arid climate.…”

“…The threshold fidelity value for diagnostic species was 30%, while the cut-off frequency value for constant species was 40%, and 10% for dominant species (Marcenò et al 2018). This follows standard procedures used for the Vegetation Survey of the Namibia project (Strohbach 2021).…”