Transcript 22 Landscape Ecol 2009

Landscape Ecology
Large-scale Spatial Patterns and
Ecological Processes
Objectives
Spatial aspects due
to habitat heterogeneity
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Structure
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Matrix
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Mosaic
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Fragmentation creates patches
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Influences on ecosystem processes
Spatial dynamics
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Metapopulations
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Structure
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Dynamics
Small populations in patches
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Risk of extinction
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Rescue effect
Landscape ecology - focus on larger
scale with much habitat heterogeneity.
Landscape ecology:
Study of relationship between spatial
pattern and ecological processes over a
range of scales.
Includes human influences
A mosaic of habitat types - both
terrerestrial and aquatic - of varying
shapes and sizes.
Landscape mosaics
reflect natural and
human influences from the past….
…and from the present
Animals can alter
landscape mosaic
…an ecosystem
engineer!
Humans as most impressive ecosystem
engineers…create a mosaic of habitat types.
Landscape info gathered from satellite (here
using reflected wavelengths in visible
spectrum).
…or from wavelengths in visible + nearinfrared spectrum (vegetation = bright red)
Remote sensing
used to quantify
landscape features.
Y axis = how well amount of wetland habitat at
different distances from local wetland affects
species presence locally? Which distance explains
best for species a? species c?
What is the ‘take-home message’?
Components of landscape structure:
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Size (area)
Shape
Number
Position and pattern
….of patches (or landscape elements)
in a landscape
Landscape structure…
influences ecological processes:
• Flow of energy
• Flow of materials
• Movement of species
….across a landscape
• Small population dynamics/genetics
• Species interactions/community dynamics
Fragmentation: creation of habitat patches
What are effects of fragmentation on
landscape pattern?
• Total amount of habitat….
• Number of habitat patches…
• Amount of edge habitat…
• Average patch size…
• Patch isolation…
How does habitat area affect species
richness?
Figure 2
How does fragmentation affect prevalence of
Lyme disease?
Figure 3
Many aspects of ecology are affected by:
habitat fragmentation + ‘edge effects’ = ?
What happens to amount of edge habitat with
habitat fragmentation? What happens to
‘edge specialists’? Interior specialists?
Fragmentation, edge effect, and cowbird
parasitism
How does cowbird parasitism change from
the edge into the interior of the forest?
Are cowbirds edge- or interior-specialists?
Figure 4
Question: Does fragmentation affect forest
‘quality’?
• Hypothesis: Fragmentation reduces forest
quality (e.g. tree growth and survival).
• Prediction: Species diversity and biomass
will be lower in forest fragments
compared to forest interior, especially
along edges.
Minimum Critical Fragment Size Study
What is the question being addressed?
Describe the results.
What data are missing before a conclusion
is reached?
Figure 5
How does fragment shape affect edge/interior
habitat? Which has most edge (same area)?
Figure 6
Patch
• Relatively homogeneous area that
differs from its surroundings
Mosaic: pattern of patches
• Formed by patches within landscape
Matrix
• Background in which mosaic imbedded; most
continuous element within landscape
Habitat fragmentation --> suitable habitat
patches separated by unfavorable habitat
Figure 7
Habitat patchiness has led to 3 models of
populations:
Metapopulation = population divided by
habitat heterogeneity into subpopulations
with varying amounts of migration between
patches.
Intervening
habitat
(matrix) --->
barrier to
movement
***What determines if a matrix is a
barrier to movement?
• Distance between subpopulations
• Nature of intervening habitat
• Mobility of species
***What factors would be incorporated in a
model of metapopulation dynamics of
mountain sheep?
Figure 8
Factors that metapopulation dynamics
depend upon:
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birth and death within each subpopulation
migration between patches
colonization to form new subpopulations
extinction of existing subpopulations
•
Connectivity influences metapopulation
dynamics.
What features help to diminish the effects of
fragmentation on movement?
• Corridors - continuous connection
between patches
• Stepping stones - small intervening patches
between large patches of favorable habitat
• Which type of organism (fliers vs. nonfliers) requires which type of connection?
Experimental patches used to study
effects of habitat corridors
What is the main conclusion of the effect of
corridors on movement?
Figure 9
• ***Summarize the major result for:
•
A. shrew B. moth
• Patches vary in size, habitat quality, + degree
of isolation.
Figure 10
How do corridors affect gene flow?
Inbreeding? genetic cohesion of metapop?
Figure 11
Why did these genetic differences between
populations in small, isolated patches arise?
Figure 12
How to study whether
organisms respond to
landscapes at different
scales.
Elements of scale:
Grain = resolution
Size = extent
Do different types of bees respond differently
to landscape scale of semi-natural habitats?
Does scale perceived/used differ with
different activities and life stages?
Figure 13