Quantifying Landscape / Ecological Succession
251
plant ecology. Aerial photographs can be used to identify and delineate plant
assemblages at the physiognomic or formation levels (Howard, 1970).
The concept of a photo-community, refers to a distinct assemblage of plant
species discernible in (stereo-pairs of) aerial photographs at a specified scale. This
concept, however, has its limitations, since the photo-community varies not only with
scale but also with several other factors such as photo texture, tone etc. In this study,
the photo-community concept has been used to a limited extent, but the emphasis has
been more towards the delineation of habitats and vegetation densities. The vegetal
association of the habitats has been inferred with the assistance of recent vegetation
maps and ground checks.
Methodology
The methodology adopted in this study is similar to that used by Hartog et al. (1992).
Thus, we have visually interpreted the aerial photographs (Table 1) based on the keys
developed by Hartog et al. (1992), although these will not be described here. Figure 2
shows aerial photographs of the northern part of the study area acquired during 1962
and 1994.
Clearly, there are limitations to the ability to identify and map the many types
of vegetation species and communities in Kenfig NNR using panchromatic or colour
aerial photographs, the most important ones being the spatial scale and spectral
limitations of these media.
As mentioned earlier, the focus of studies of ecological diversity and nature
conservation has shifted from species to habitats, with this change in emphasis
accelerating in recent years. This general observation is also true for Kenfig NNR,
where loss of habitat has been the major cause for concern among the nature reserve
managers. Consequently our aim has been to map habitats based on a visual
assessment of vegetation density and structure in aerial photographs. Taking into
account the nature of the study, the scale of photographs used, and the structure of the
vegetation at Kenfig NNR, a simplified classification of habitats was produced (Table
2).
The habitat maps generated from the aerial photographs were digitised using
a semi-automatic approach involving scanning, conversion to grids, and then semiautomatic digitising. The vector coverages generated in this way were subsequently
geo-referenced, co-registered and rectified with reference to control points derived
from Ordnance Survey maps of 1:10000 scale.
The Haul road which runs parallel to the coast along the western margin of
the NNR was laid after 1962 and has had an influence on the morphology of the dunes,
vegetation and hydrology of the adjoining areas (Jones, 1993). To have a common area
of study before and after 1962, the Haul road has been used as the western boundary
and has been superimposed on the habitat map of 1962. A similar procedure was
251
plant ecology. Aerial photographs can be used to identify and delineate plant
assemblages at the physiognomic or formation levels (Howard, 1970).
The concept of a photo-community, refers to a distinct assemblage of plant
species discernible in (stereo-pairs of) aerial photographs at a specified scale. This
concept, however, has its limitations, since the photo-community varies not only with
scale but also with several other factors such as photo texture, tone etc. In this study,
the photo-community concept has been used to a limited extent, but the emphasis has
been more towards the delineation of habitats and vegetation densities. The vegetal
association of the habitats has been inferred with the assistance of recent vegetation
maps and ground checks.
Methodology
The methodology adopted in this study is similar to that used by Hartog et al. (1992).
Thus, we have visually interpreted the aerial photographs (Table 1) based on the keys
developed by Hartog et al. (1992), although these will not be described here. Figure 2
shows aerial photographs of the northern part of the study area acquired during 1962
and 1994.
Clearly, there are limitations to the ability to identify and map the many types
of vegetation species and communities in Kenfig NNR using panchromatic or colour
aerial photographs, the most important ones being the spatial scale and spectral
limitations of these media.
As mentioned earlier, the focus of studies of ecological diversity and nature
conservation has shifted from species to habitats, with this change in emphasis
accelerating in recent years. This general observation is also true for Kenfig NNR,
where loss of habitat has been the major cause for concern among the nature reserve
managers. Consequently our aim has been to map habitats based on a visual
assessment of vegetation density and structure in aerial photographs. Taking into
account the nature of the study, the scale of photographs used, and the structure of the
vegetation at Kenfig NNR, a simplified classification of habitats was produced (Table
2).
The habitat maps generated from the aerial photographs were digitised using
a semi-automatic approach involving scanning, conversion to grids, and then semiautomatic digitising. The vector coverages generated in this way were subsequently
geo-referenced, co-registered and rectified with reference to control points derived
from Ordnance Survey maps of 1:10000 scale.
The Haul road which runs parallel to the coast along the western margin of
the NNR was laid after 1962 and has had an influence on the morphology of the dunes,
vegetation and hydrology of the adjoining areas (Jones, 1993). To have a common area
of study before and after 1962, the Haul road has been used as the western boundary
and has been superimposed on the habitat map of 1962. A similar procedure was