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ENV510 Landscape Ecology and GIS
Definitions
& descriptions |
Structure
& pattern | Function
& process | Change
& dynamics | Management
implications
Processes
| Elements | Transformation
| Fragmentation | Forest
& Birds | Ecosystem
| Other
Canopy
height and isolation
Vegetation characteristics
Variable response
The impacts of fragmentation on bird populations are very complex and often
species specific. The general consensus is that fragmentation of the landscape
into isolated patches can adversely affect some bird species. However, structural
and floristic changes to the patch are often more important than patch size
and isolation for bird communities (Lynch
and Whigham, 1984).
Robbins (1980) statistically analysed the relative contributions that vegetation factors, isolation and area of patch, had on bird community composition. He found that canopy height and forest isolation were consistently the most important predictors of abundance for the 51 bird species he analysed. These factors accounted for 21 significant correlations whereas patch area accounted for 6 significant correlations.
Lynch
and Whigham (1984) showed that within a range of patch areas (5-1000 ha)
and isolations (0.1-1km), it was vegetation characteristics rather than patch
geometry that had a dominant role in determining the community composition and
local abundance of bird species. This means that species distribution is related
to a complex interrelationship between area, isolation, canopy height, tree
density and other habitat characteristics rather than one specific patch characteristic.
Some
species seem to be tolerant of a certain degree of habitat disturbance. They
can make use of the edge habitat that can be introduced because of fragmentation
quite well. Others, eg highly migratory species, tend to respond negatively
to habitat fragmentation and a reduction in floristic and structural diversity
of breeding habitat.
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