Appendix A3
Proposal for Ph.D studies to be carried
out at Phugwane site by Mr S. Levin of
University of Witwatersrand
Context, structure and dynamics of riparian/savanna boundary vegetation patch
mosaics: A scaled perspective
Shaun Levick
Centre for Water in the Environment
University of the Witwatersrand
Outline:
My PhD work falls under the River/Savanna Boundaries Program (RSBP). The RSBP is
primarily concerned with the structure and function of riparian boundaries in savanna
landscapes. Boundaries are considered to be important control points in the landscape
that mediate flows between the adjacent patch types. Boundaries are also recognised as
locations of high biodiversity and are dynamic elements that may provide useful
indicators of change in the landscape.
My work is focused on the four main rivers of the Shingwedzi drainage network
(Mphongolo, Phugwane, Bububu & Shingwedzi). These rivers are flanked by old
floodplains and alluvial deposits. The alluvial soils form a boundary between the
riparian zone and the upland. The boundary zone is characterized by extensive bare
areas which are sodic in nature. This area is of research interest for a number of reasons:
1) The boundary is a complex mosaic of different patch types – bare areas lay
adjacent to patches of really tall trees on the same substrate – pattern does not fit
the general catena model
2) The boundary zone is a hotspot of herbivore activity – elephants and impala
heavily utilise the vegetation of the sodic sites – high concentrations of Na, N &
C
3) The boundary zone is dynamic – Khomo (1999) found that bare areas in this
zone have increased 3 fold in areal extent over a 50 year period. Such rapid
changes are of concern to KNP managers who aim to maintain biodiversity
My primary aim is to develop an understanding of the spatial and temporal dynamics of
the vegetated-bare soil patch mosaic that comprises the boundary zone. I will use a
hierarchical patch dynamics approach to investigate the structural and dynamic
attributes of the boundary patch mosaic. Central themes at multiple scales include:
1) The influence of spatial context on the structure, composition and dynamics of
the boundary patch mosaic
2) The influence of age and history of boundaries on their structure and dynamics
3) The role of plant and animal organisms as ecosystem engineers in modifying
boundary structure and composition
4) Implications of dynamic mosaics for management
A LiDAR scan was conducted in November 2003 which has provided high resolution
digital aerial colour photographs, ground points with 10cm vertical accuracy and
vegetation canopy heights for all for four rivers. This data will allow for the accurate
spatial representation of patch types based on both vegetation species and height
classes. Aerial photographs dating back 60 years and a 27 year fixed point photograph
record provide the opportunity to assess changes in vegetation cover and structure over
time. The alluvial deposits of the four rivers appear to be of different ages and therefore
hold the potential to provide answers regarding the influence of temporal context on
boundary structure and function.
Figure showing a RS image of study sites on the Phugwane tributary of the Shingwedzi.