Variegation
Need for a new model
Variegated landscapes
Rangelands variegation
The fragmentation model applies to the Kellerberrin
study area and many cultural landscapes in Europe and North America where
it was originally developed, however it may not be applicable to landscape
transformation in all areas (McIntyre
and Barrett, 1992), especially grassy landscapes.
The concept of fragmentation implies remnants are isolated by areas that are hostile to the organisms within the remnants so species that persist in this sort of landscape need to rely on corridors or long distance dispersal to move between patches. This may be the case in the wheatbelt of WA, but in the New England tablelands of NSW, land transformation has taken place in a different way. This may have caused you some difficulty with the fragmentation activity.
Variegated landscapes are described as
being 'where native vegetation still forms the matrix
but has been modified in a variable way' (McIntyre,
1994).
A variegated landscape approach is very
relevant to understanding the effects of disturbance in rangelands and
forestry land use types throughout Australia.
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If you are interested in this area you might like to read the McIntyre and Barrett article "Habitat Variegation: An alternative to fragmentation". | |
Variegated
landscapes in the rangelands
Rangelands can be described as being variegated
because native vegetation makes up the matrix but the native vegetation
has been modified in some way.
This means that remnant vegetation exists
in a 'sea' of native vegetation that is modified to different extents
but not totally removed. So, in this model of the landscape, modifications
are represented as a gradient of change rather than discrete sharp boundaries
as the fragmentation model suggests. Continuous variation across the landscape
exists in locations that have undergone this form of transformation.
The implications of this type of transformation
for ecosystem flows and processes will be different from those found in
a fragmented and relictual
landscape.
