Abstract:
The extreme variability in the topography, altitude and climatic conditions in the temperate
Grassland Mountains of Southern Africa is associated with the complex mosaic of grassland
communities with pockets of woodland patches. Understanding the relationships between
plant communities and environmental parameters is essential in biodiversity conservation,
especially for current and future climate change predictions. This article focused on the spatial
distribution of woodland communities and their associated environmental drivers in the
Golden Gate Highlands (GGHNP) National Park in South Africa. A generalized linear model
(GLM) assuming a binomial distribution, was used to determine the optimal environmental
variables influencing the spatial distribution of the woodland communities. The Coefficient of
Variation (CV) was relatively higher for the topographic ruggedness index (68.78%),
topographic roughness index (68.03), aspect (60.04%), coarse fragments (37.46%) and the
topographic wetness index (31.33) whereas soil pH, bulk density, sandy and clay contents had
relatively less variation (2.39%, 3.23%, 7.56% and 8.46% respectively). In determining the
optimal number of environmental variables influencing the spatial distribution of woodland
communities, roughness index, topographic wetness index, soil coarse fragments, soil organic
carbon, soil cation exchange capacity and remote-sensing based vegetation condition index
were significant (p < 0.05) and positively correlated with the woodland communities. Soil
nitrogen, clay content, soil pH, fire and elevation were also significant but negatively
correlated with the woodland communities. The area under the curve (AUC) of the receiver
operating characteristics (ROC) was 0.81. This was indicative of a Parsimonious Model with
explanatory predictive power for determination of optimal environmental variables in
vegetation ecology.
CONSERVATION IMPLICATIONS : The isolated woodland communities are sources of floristic diversity and important biogeographical links between larger forest areas in the wider
Drakensberg region. They provide suitable habitats for a larger number of forest species and
harbour some of the endemic tree species of South Africa. They also provide watershed
protection and other important ecosystem services. Understanding the drivers influencing the
spatial distribution and persistence of these woodland communities is therefore key to
conservation planning in the area.
