Abstract:
Southern African mountain ranges are characterised by rich and diverse plant species thriving
in different habitats with pronounced endemic species. However, globally, biodiversity at the
species level is deteriorating rapidly because of environmental change leading to habitat
degradation and fragmentation. Mountainous grassland communities are particularly
vulnerable to rapid ecosystem changes because of their specialised niches and sensitivity to
global warming. Understanding the determinants of vegetation is necessary for effective and
efficient management. This study aimed to determine significant environmental drivers
influencing plant species richness in mountainous mesic grasslands. Topographical variables
(slope and elevation) were derived by using a 30 m resolution Digital Elevation Model. Soil
variables such as bulk density, silt fragments, pH, coarse fragments, soil organic carbon, sand
and nitrogen were acquired from the International Soil Conference and Information Centre
(ISCI), and species richness and diversity were derived from vascular plant species inventory
data compiled using a field survey. Species richness was influenced by soil bulk density, and
the interaction between elevation and soil bulk density; higher species richness was associated
with lower bulk density and higher elevations. Similarly, species composition changed as
edaphic factors and elevation changed.
CONSERVATION IMPLICATIONS : Species richness increased with soil bulk density, which decreased
with elevation. Fire severity had little effect on species richness and diversity, which may
indicate that management actions do not affect species. However, the impact of grazers still
needs to be better understood at this time. Moreover, the strong positive relationship between
species richness and diversity in this study shows that species richness can be used as a
surrogate for diversity and conservation monitoring, especially in mesic highland grasslands.
