Quantifying Landscape / Ecological Succession
259
successional trend in the dunal system, an attempt was made to demarcate slack areas
that are undergoing rapid transition due to hydrological factors. The dune slacks at
Kenfig NNR were classified into one of four types by Jones (1993) based on their
hydrological status:
Type 1 slacks are typified by very shallow winter-flooding. During periods of
flooding the water table displays a subdued response even to prolonged periods of
heavy rainfall.
Type 2 slacks are similar to the above, but flood to a greater depth. The depth of
flooding rarely exceeds 30cm, however, and for most dip-wells in the group was
found to lie between 10cm and 25cm;
Type 3 are characterised by deep winter-flooding; and
Type 4 slacks are characterised by extremely deep winter-flooding.
A vector (point) coverage consisting of 192 dip-well locations (Jones 1993) C
together with their corresponding hydrological characteristics (hydro-type/attribute) C
was combined with the habitat change vector maps. This indicated that: (i) slack types
2 and 3 are the most vulnerable to transition to denser vegetation types; (ii) faster
vegetation growth occurred in areas originally characterised by slack types 2 and 3;
and (iii) after becoming moderately vegetated, hydrological factors have little impact
on the transition into dense slack and woodland.
Limitations of this Study
The most difficult (and perhaps error-prone) part of studies such as this is rectification
of the aerial photographs to some reference map projection. Although the utmost care
was taken in geo-referencing the photographs and rectifying them, the scale of the
photographs was different for each date, so that distortion and subsequent error in
matching may have resulted in a small percentage of error creeping in the geometry of
the vectors and eventually in the change statistics. A second consideration is that
colour photographs, had they been available for all the years under consideration,
would have provided more reliable information on vegetation type and density.
Conclusions
The general conclusion that can be drawn from the integration of aerial images and
GIS used in this study is that, while the processes of erosion and dune mobility were
active at Kenfig NNR at the start of the period considered (1962-1994), the dunes have
become increasingly stabilised and there has been a cessation of dune-slack generation.
It was also noted that the greening of the dunes has been slower than that of the slacks,
and that at least 25% of the slacks could be restored to the conditions that support the
survival of rare and pioneer species given appropriate management practices.
Habitat monitoring is an important prerequisite to the management of coastal
dune systems, which are highly dynamic in nature. Aerial photographs provide a
259
successional trend in the dunal system, an attempt was made to demarcate slack areas
that are undergoing rapid transition due to hydrological factors. The dune slacks at
Kenfig NNR were classified into one of four types by Jones (1993) based on their
hydrological status:
Type 1 slacks are typified by very shallow winter-flooding. During periods of
flooding the water table displays a subdued response even to prolonged periods of
heavy rainfall.
Type 2 slacks are similar to the above, but flood to a greater depth. The depth of
flooding rarely exceeds 30cm, however, and for most dip-wells in the group was
found to lie between 10cm and 25cm;
Type 3 are characterised by deep winter-flooding; and
Type 4 slacks are characterised by extremely deep winter-flooding.
A vector (point) coverage consisting of 192 dip-well locations (Jones 1993) C
together with their corresponding hydrological characteristics (hydro-type/attribute) C
was combined with the habitat change vector maps. This indicated that: (i) slack types
2 and 3 are the most vulnerable to transition to denser vegetation types; (ii) faster
vegetation growth occurred in areas originally characterised by slack types 2 and 3;
and (iii) after becoming moderately vegetated, hydrological factors have little impact
on the transition into dense slack and woodland.
Limitations of this Study
The most difficult (and perhaps error-prone) part of studies such as this is rectification
of the aerial photographs to some reference map projection. Although the utmost care
was taken in geo-referencing the photographs and rectifying them, the scale of the
photographs was different for each date, so that distortion and subsequent error in
matching may have resulted in a small percentage of error creeping in the geometry of
the vectors and eventually in the change statistics. A second consideration is that
colour photographs, had they been available for all the years under consideration,
would have provided more reliable information on vegetation type and density.
Conclusions
The general conclusion that can be drawn from the integration of aerial images and
GIS used in this study is that, while the processes of erosion and dune mobility were
active at Kenfig NNR at the start of the period considered (1962-1994), the dunes have
become increasingly stabilised and there has been a cessation of dune-slack generation.
It was also noted that the greening of the dunes has been slower than that of the slacks,
and that at least 25% of the slacks could be restored to the conditions that support the
survival of rare and pioneer species given appropriate management practices.
Habitat monitoring is an important prerequisite to the management of coastal
dune systems, which are highly dynamic in nature. Aerial photographs provide a