Abstract:
The Hantam–Tanqua–Roggeveld subregion falls within the Succulent Karoo and Fynbos
Biomes, which are both recognised as global biodiversity hotspots that should be conserved.
The objective of this study was to gather baseline biodiversity information that can be used
to guide conservation efforts. A total of 40 Whittaker plots were surveyed in the subregion
and the various diversity parameters calculated from the data were compared across the
subregion and to available data for the Succulent Karoo and Fynbos Biomes. Species richness
per 1000 m2 ranged from nine to 100 species across the subregion. Species richness for all
plot sizes < 1000 m2 was significantly lower for the Tanqua Karoo than for both the Winter
Rainfall Karoo and Mountain Renosterveld. The latter two areas did not differ significantly
from each other with regard to species richness. Species richness was significantly higher
only at the 1000 m2 scale in the Mountain Renosterveld compared to the Winter Rainfall
Karoo. Evenness and Shannon and Simpson indices did not differ significantly between the
Mountain Renosterveld and Winter Rainfall Karoo; however, these values were significantly
higher than for the Tanqua Karoo.
A principal coordinate analysis of species richness data at seven plot sizes produced three
distinct clusters. One cluster represented the Tanqua Karoo, with low species richness,
evenness, and Shannon and Simpson indices. Another cluster represented mostly Mountain
Renosterveld vegetation, which was characterised by a high species richness, evenness, and
Shannon and Simpson indices. The third cluster was formed by the remaining Mountain
Renosterveld plots as well as the Winter Rainfall Karoo plots.
The high species richness values found in the various vegetation units can add valuable
information to the conservation planning arena by providing information on biodiversity
parameters and their spatial distribution. This information can assist with conservation
efforts in the Hantam, Tanqua and Roggeveld areas.
CONSERVATION IMPLICATIONS: Conservation and development of the Hantam–Tanqua–
Roggeveld subregion is hampered by a lack of information on floristic diversity. The results
of the current study indicated areas of low diversity and contrasting areas of high diversity.
These data can be used to guide effective conservation and management of the floristic
diversity.
