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Research Article

The composition of the soil seedbank and its role in ecosystem dynamics and rehabilitation potential in the arid Tankwa Karoo Region, South Africa

Published in: African Journal of Range & Forage Science
Volume 35, issue 3-4, 2018 , pages: 351–361
DOI: 10.2989/10220119.2018.1526824
Author(s): Manam WB SaaedHigher Institute of Agricultural Techniques, Libya, Shayne M JacobsDepartment of Conservation Ecology and Entomology, South Africa, Mmoto L MasubeleleCape Research Centre, South Africa, Igshaan SamuelsAgricultural Research Council–Animal Production, c/o Department of Biodiversity and Conservation Biology, South Africa, Lesego KhomoDepartment of Environmental Sciences, South Africa, Yacoub M El-BarasiBotany Department, Faculty of Science, Libya

Abstract

Very few soil seedbank studies have been conducted in South Africa, especially in arid rangelands. Insight into the soil seedbank could therefore improve assessment of rangeland dynamics and enhance rehabilitation efforts. This study aimed to characterise the soil seedbanks in various vegetation types of the Tankwa Karoo National Park, an arid environment in South Africa. At 43 sites soil was sampled twice at the end of spring and the end of autumn, and the composition and structure of aboveground vegetation were described at the peak growth period in spring. Seeds were isolated from the soil samples by means of flotation in a salt solution, seedbank species composition was obtained by seedling germination, and the vegetation was investigated using a line-point survey method. Overall seed density was 8 034 seeds m−2 of which 55% was viable, and the common life-forms were therophytes and chamaephytes. Species richness and diversity were lower in the seedbank compared with those of the vegetation, and the two vegetation spheres were 25% similar. While seedbank composition suggested poor veld condition, there was enough seed density and viability for future regeneration and rehabilitation initiatives. However, this may be impeded by the absence of many perennial species in the soil seedbank.

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