The effect of overlapping piospheres on landscape heterogeneity

In 1933, Kruger National Park implemented artificial sources of surface water. Many studies have
been conducted on the effect these waterholes have on herbivore distribution and the related
impacts. One such finding is that piospheres, patches created by herbivores through their grazing,
browsing and trampling activities focusing around a water source (Owen-Smith 1996 cited in
Gaylard et al 2002) occur around waterholes and contribute to the patchiness in the landscape. The
aim of this study was to determine if the proportion of increaser II grass species would drop below
50% and be replaced by decreaser grass species at a shorter distance away from the closer spaced
water holes than from the isolated water hole and to determine if the vegetation between two closely
spaced water holes will be dominated by increaser II grass species. Two sites were selected, one
with an isolated water hole and one with two closely spaced water holes. Transects were preformed
at increasing distances from each water hole, and grass species were recorded along these transects
at 2m intervals. Our data supported our hypotheses. We found that transects going away from an
isolated water hole and transects going away from two closely spaced water holes changed from a
system dominated by increaser II grasses to a system dominated by decreaser grass species. The
transects running between the two closely spaced water holes, however, never became dominated
by decreaser grass species. The area between the two closely spaced water holes was an example of
increased homogeneity on a small scale; however, when looked at on a large scale the space in
between the water holes creates a distinct patch in the ecosystem that is supportive of a certain type
of grazer.