Grasslands of the World.pdf - Disasters and Conflicts - UNEP

Grasslands of South Africa 113
framework for exploring rehabilitation within the context of an understanding
of landscape function. Ludwig et al. (1997) suggest that the landscape comprises
a series of inter-connected patches, with resource control being a key feature
in the maintenance of the integrity of the landscape. Nutrients and moisture
move from one patch to another, mainly though water flow patterns. The
obstructions or patches in the landscape prevent nutrients from being lost, with
run-on areas acting as sites of nutrient and moisture accumulation. Run-on
areas are connected to one another by runoff zones or fetches. In a degrading
landscape, it is suggested that these runoff areas increase in size and the run-on
areas can no longer capture and accumulate nutrients, and so nutrients are lost
to rivers and transported away from the landscape. In order to quantify these
processes and relate them to South Africa n landscapes, landscape function
analysis (LFA) (Ludwig et al., 1997) was applied to two contrasting land use
types (Palmer et al., 2001). The results showed that landscape with a long
history of communal management has surface accumulations of C and N,
which may not have been processed efficiently. Although Palmer et al. (2001)
did not investigate nutrient loss, there were significant differences between landscape-scale
organizations, with communal landscape having a lower landscape
functionality index than the freehold grassland . There was greater patchiness
in the communal landscape, with longer fetches than the landscape with a long
history of commercial management. In accordance with Ludwig et al. (1997),
it is recommended that rehabilitation of degraded rangelands in South Africa
should strive to reduce the extent of runoff zones and increase the resource
control exercised by patches.
Spatially explicit diversity indices (moving standard deviation index) have
been applied to near-infrared (NIR) imagery (Landsat TM and SPOT) (Tanser
and Palmer, 1999) recorded over land with different management histories and
condition classes. Degraded grasslands, located in areas with a long history of
communal management, had higher spatial diversity of selected growth indices
than healthy grassland . Grasslands, savannahs and thicket with a high standing
biomass and a long history of conservative land management, showed low
spatial diversity indices. Rehabilitation techniques should attempt to reduce
landscape photosynthetic heterogeneity.
Over-seeding with commercially available seeds has long been regarded as a
solution to rehabilitation of degraded rangeland. In the thicket biome , re-vegetation
of former cultivated lands has been successful when lime-coated seed
(a mixture of seven local species, including Panicum maximum , Cenchrus ciliaris
and Eragrostis curvula ) was broadcast over the cultivated land and a long
(three-year) rest applied. However, there has been limited success reported
elsewhere, where commercial seeds generally require irrigation after planting
and any early effect is usually discounted within a few years.
Using the principles embodied in the LFA theory, Van Rooyen (2000) has
shown that it is possible to rehabilitate degraded biospheres in the southern