Field Operations Manual for Herbivore & Fire Exclosures on the Sabie and Letaba Rivers in the Kruger National Park

This cooperative program builds on the extensive knowledge base generated by
the many decades of research conducted by the Kruger National Park Scientific Services,
and the decade-long Kruger National Park River Research Program and more recent
River Savanna Boundaries Program in collaboration with several South African and
American universities, government departments, and research agencies. The Kruger Park
has a long history of interest in the possibility of erection of formal research exclosures
(rather than the “incidental exclosures” which have become available because of for
instance, enclosures being built to breed up rare antelope). This interest relates
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particularly relating to fire and elephant effects. Fortunately this historical interest, and
the more recent interest of other groups in riparian and riparian-upland issues in the
Kruger Park, has provided an opportunity for unified structures dealing with all these
interests, to be put in place.
In February 2000 the Kruger National Park was presented with a unique
opportunity to develop a long-term experiment designed to examine the effects of
herbivory. The largest flood since 1925 for the Sabie (7,000 to 8,000 m3 s-1) and Letaba
rivers removed most of the vegetation along these rivers, primary research sites in the
park, resetting the system to bedrock and sand. The vegetation before the flood was a
mature riparian forest including stately fig and other majestic riparian trees. The Sabie
River catchment is 7,086 km2 with a river length of 230 km and a mean discharge of 633
million m3/a. The Letaba catchment is 13400 km2 with a length of 490 km and a mean
discharge of 631 million m3/a.
Construction of large exclosures subsequent to this major flood event will allow
us to follow the successional development and pattern formation of vegetation along
riparian zones. Riparian zones are recognized as “hotspots” of activity because they
integrate terrestrial and aquatic systems (Naiman and Décamps 1997). We believe the
research we are conducting (viewed across aquatic, riparian and upland zones) will
generate a novel understanding of savannas as integrated yet heterogeneous ecological
systems.
The systems approach to ecosystem study requires ecologists to expose the
connections and fluxes between the elements of heterogeneity, and the feedbacks
between heterogeneity and ecosystem function (Risser 1995). Therefore, boundaries in
the landscape that define this heterogeneity are of particular ecological interest, and
riparian corridors are perhaps the most obvious expression of boundaries in savanna
regions.
The emerging view of system heterogeneity emphasizes that biological richness
has many facets (Noss and Cooperrider 1994). The first facet highlights the kinds of
ecological systems that are present in a region. The second facet indicates the relative
abundance of each kind of entity present in the area. The third facet indicates that the
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various ecological components are dynamic in time, and that they are functionally
connected with one another. Finally, the three facets of kind, relative abundance, and
function are expressed in all ecological realms. Therefore, genes, species and
populations, communities and ecosystems, and landscapes all can be considered as
components of system heterogeneity (Kolasa and Pickett 1991, Collins and Benning
1996). Riparian systems, and their connection to in-stream processes and to interchanges
with the upland components of savanna landscapes, provide a powerful test of the
functional significance of spatial and temporal ecosystem heterogeneity. The
development of this understanding is the overarching mission of our scientific
programme.