Thursday, March 15, 2007

Penhill’s Natural Vegetation

Penhill is a small community across the railway line from the rest of Eersterivier, which lies roughly south-west and south of Penhill. To the south-east of Penhill is a quarry for slate. East of Penhill is an old field. The undeveloped hill top to the north-east (approximately 33o59’24.32”S; 18o44’31.71”E) is covered by Sand Plain Fynbos (Vegetation Type No. 68, Low & Rebelo 1996) with some West Coast Renosterveld (Vegetation Type No. 62, Low & Rebelo 1996)where the soils are granitic. To the north of Penhill are farmlands. Another remnant of Sand Plain Fynbos lies north-west to west of Penhill (approximately 33o59’23.94”S; 18o43’51.65”E). This essay concerns the Sand Plain Fynbos remnants.

The Sand Plain Fynbos contains the typical components of Fynbos: a restioid component, a proteoid component, a geophytic component and an ericoid component. In the Penhill remnants, the natural structure of the vegetation is open shrubland. Of the species listed by Low & Rebelo (1996) as characteristic of Sand Plain Fynbos, the following definitely occur in the Penhill remnants: Erica mammosa (Fig. 1), Phylica cephalantha and Phylica stipularis. Phylica cephalantha is one of the dominants in the Penhill remnants. The pictures were taken in October 2006 and show a few of the species occuring in the north-west to west Penhill remnant.

Figure 1: Erica mammosa

Figure 2: A Tritonia sp.

Figure 3: Leucospermum hypophyllocarpodendron

Sand Plain Fynbos occurs on acid sands which are low in nutrients (Low & Rebelo 1996). The presence of Mediterranean grasses indicates that the soils of the Penhill remnants have been enriched – possibly by agricultural runoff (see Piessens et al. 2006) and the action of the woody legume invaders.

The Penhill remnants of Sand Plain are isolated from other Sand Plain Fynbos by urban development and agricultural land and are threatened by both agriculture and urban development.

The natural vegetation of Penhill has not been managed for conservation. Eskom brushcuts parts of the north-western remnant because of its proximity to major power lines. Both remnants suffer from too frequent burning. The frequent fires have favoured alien species resulting in dense invasions in places. The main woody alien is Acacia saligna. Acacia cyclops and Eucalyptus sp. are also present.

In conservation terms, Penhill falls within the Peninsula District centre of endemism within the Sand Plain Fynbos. In 1996, none of the vegetation of this centre of endemism was formally conserved (Low & Rebelo 1996). (The University of the Western Cape has a remnant of this vegetation but while some of it is adjacent to the Cape Flats Nature Reserve and presently managed with the reserve, it is not formally part of the reserve and is threatened by development of the university.) The Penhill remnants are thus valuable and should be formally conserved.

Low, A.B. & Rebelo, A.G. (1996) Vegetation of South Africa, Lesotho and Swaziland, Department of Environmental Affairs and Tourism, Pretoria. 0-621-17316-9 ISBN

Piessens, K., Honnay, O., Devlaeminck, R. & Hermy, M. (2006) Biotic and abiotic edge effects in highly fragmented heathlands adjacent to cropland and forest. Agriculture, Ecosystems and Environment 114: 335—342.

1 comment:

David said...

Thanks for this information. Interested Penhiller.