Biology Reference
In-Depth Information
Box 2.7.
A tree regeneration crisis in temperate woodlands?
Eucalypt regeneration is virtually always present in relatively unmodified woodland
remnants.
3
In a study in the wheat-sheep belt of New South Wales, however, only
38% of remnants on freehold land contained eucalypt regeneration.
31
The key fac-
tors associated with the occurrence of regeneration were grazing, exotic plant cover
and remnant size. Remnants that were large, with light or intermittent grazing by
stock and a high cover of understorey native plants were most likely to contain
regeneration. If we don't address the regeneration crisis then a considerable area of
remnant woodland will disappear across the wheat-sheep belt over the next cen-
tury. Excluding livestock grazing from small remnants, grazing small remnants with
stock intermittently, controlling rabbits or planting seedlings in gaps within and
around small remnants are the principal solutions. But these actions must be under-
taken at a large scale across the wheat-sheep belt if we are to avert a tree regenera-
tion crisis.
grazing.
20, 26, 27
Reducing the amount of fertiliser that is used in an area also can
promote the natural regeneration of overstorey woodland trees.
Remnant size
The value of large remnants
A general theme in conservation science is that bigger patches of native vegetation
are better than smaller ones because they typically support more species and larger
numbers of individuals of any given species. At least seven interrelated reasons
have been proposed to explain this widespread pattern:
More kinds of habitat can occur in larger patches, thereby providing niches for
more species.
●
Larger patches have more resources (e.g. food and shelter sites) and a greater
range of resources, allowing them to support more individuals of a particular
species.
●
Individual animals that are moving across a landscape may be more likely to
find (and then settle) in larger patches.
●
Following major disturbances such as bushfires, larger patches are more likely
to contain areas of undisturbed habitat where disturbance-sensitive species can
survive.
●
Rates of predation of the nests of native birds are lower in large patches,
particularly away from the edges of these patches.
●
Larger patches have more 'core' area relative to 'edge' area. Patch edges can
suffer more disturbances and support poorer habitat for many species.
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