Vegetation of the Thornbush Savanna of Central Namibia: Baseline description of the present vegetation at Farm Erichsfelde, Otjozondjupa Region

Authors

  • BJ Strohbach Namibia University of Science and Technology

Keywords:

Acacietea, Livestock Farming Suitability Index, Modified TWINSPAN, Nonmetric Multidimensional Scaling, Phytosociology, Veld degradation

Abstract

The Vegetation Survey of Namibia project has been initiated to provide baseline data in support of sustainable land-use planning. The finding of historical data from the Farm Erichsfelde initiated a long-term monitoring programme. This study serves as a baseline description of the vegetation associations. Regular Braun-Blanquet type sampling was done in April 1999, and additional relevés were obtained from the BIOTA project from 2002 and 2005. The entire data set comprised 232 relevés with 379 species. The data were classified using the modified TWINSPAN procedure. Eleven associations, grouped into five habitat types, were identified from the classification. These habitat types are linked to landscape facets, being wetlands, rocky habitats, plains, soils on calcretes as well as riverine and related habitats. The associations are described in terms of their composition, general position in the landscape and structure. The relevé data were subjected to an NMS ordination. The main environmental gradients identified were the topography, the soil pH and the slope of the landscape. It is, however, very clear from the ordination that the various associations identified are closely related, and in many respects ecotonal to each other. The vegetation associations were mapped using aerial images as well as the GPS position of the relevés as baseline. In addition, a Livestock Farming Suitability Index was calculated for each association, based on its habitat, composition and structure. Only the Ziziphus mucronata—Dichanthium annulatum association was rated highly suitable for livestock farming. The two plains associations, Ondetia linearis—Acacia mellifera and Aristida congesta—Acacia mellifera were rated moderately suitable, whilst all other associations were rated with a low suitability for livestock farming. The main reason for these fairly low ratings is a high degree of bush encroachment and low perennial grass cover.

Author Biography

BJ Strohbach, Namibia University of Science and Technology

My interests lie in vegetation- and landscape ecology, ranging from baseline studies to applied management options. I am leading the Vegetation Survey of Namibia project, specifically aiming at providing a baseline description of the natural vegetation of Namibia. This project covers a large variety of climatic zones, landscapes and ecosystems in Namibia. Vegetation description and mapping is done at large (regional or landscape) scale, as well as at local small-scale studies on particular farm and/or conservancies. For management purposes, the vegetation is also described i.t.o. its suitability for livestock farming as well as its sensitivity to (potential) disturbance. Vegetation is not a stable feature of the landscape, but responds to anthropogenic pressure as well as climatic drivers. Changing climate has been experienced over the past years in Namibia, and future trends are uncertain. More extreme climatic conditions are predicted for the subcontinent - bigger rain storms, more heat extremes, but also more severe dry spells. To monitor the effect of such changing climate, we are engaged with long-term monitoring of vegetation throughout the country, in collaboration with the University of Hamburg and the Gobabeb Research and Training Centre. For the purpose of long-term monitoring we have 21 biodiversity observatories throughout the country on which we regularly resurvey the plant biodiversity. These biodiversity observatories are supplemented by a number of auxiliary observatories, in which we can monitor for very specific purposes like erosion, specific plant species and -stands or lichen cover. With the annual monitoring, large emphasis is placed on monitoring using repeat aerial photography using state-of-the-art UAV technology. This technology is also used for specific applications like mapping and monitoring alien invasive species stands, stands of endemic species, as well as monitoring erosion features, and the success rate of the rehabilitation of these erosion features. A special mention is to be made of an application in the mining industry, were we are monitoring the health and success of rehabilitation work at mines with UAV technology. With the UAV technology I am combining the interesting fields of botany, vegetation ecology, remote sensing and GIS into one. I am also a keen photographer of plants and landscapes, and have contributed extensively to online plant identification guides as well as for field identification guides in the past.

Cover of Namibian Journal of Environment 2019 Volume 3

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Published

2019-05-10

Issue

Vol. 3 (2019): Namibian Journal of Environment

Section

Section A: Research articles

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Articles in this journal are licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. The copyright of all articles and field notes belongs to the authors. All other copyright is held by the journal.