ABSTRACT
Vegetation re-establishment is a necessary and critical step in achieving the goal of ecosystem
restoration on mined soils (Yan, Zhao, & Sun, 2013). This is especially important because mined soils
tend to be a poor medium for plant growth, making natural recolonisation a slow process (Wong, 2003).
Native species rehabilitation on mined soils has received much attention, but few studies have
correlated native species establishment with mined substrate properties. Currently, a knowledge gap
exists in Namibia concerning the physical properties of mined substrates and the suitability of these
substrates in supporting plant communities. This study tested the suitability of various mined substrates
for the establishment of native savanna species and explored which properties make a particular
substrate suitable for plant growth. Seven native savanna species, namely; Acacia senegal, A. tortilis, A.
erioloba, A. reficiens, A. erubescens, Catophractes alexandri and Adenolobus garipensis, were selected,
and their potential for restoration of mined soils was assessed. The seven species, grown from seeds in
the nursery, were transplanted into nine mixtures of substrates at an experimental field site at Navachab
Gold Mine, Namibia. Seedling growth and survival were monitored for 40 months. Soil samples of each
substrate were analyzed for chemical and physical properties. The highest survival percentage was
recorded in Acacia senegal followed by A. erioloba, A. reficiens, A. tortilis, Adenolobus garipensis,
Catophractes alexandri and A. erubescens. We suggest that the species survival is determined by its
range of tolerance. We found that for most species survival and growth were strongest on calcium and
clay substrates. This study showed that species were able to grow outside their natural range of soil
conditions, and all the substrates were able to support growth and survival of different species. The
survival of the study species was negatively and significantly correlated with sodium and magnesium
except for Adenolobus garipensis. The surviving seedlings were well developed and reached a large
size in three years. The results suggest that Acacia senegal, Adenolobus garipensis, Acacia tortilis and
Acacia erioloba were the most suitable candidates for the restoration of these soils, as they recorded the
highest survival and or growth and therefore showed tolerance to extreme soil conditions.
Keywords: Mined soils, Establishment, Native species, Substrate properties, Rehabilitation.