Landscape EcologyLarge-scale Spatial Patterns and Ecological Processes

ObjectivesSpatial aspects due to habitat heterogeneity• Structure• Matrix• Mosaic• Fragmentation creates patches• Influences on ecosystem processesSpatial dynamics• Metapopulations • Structure• DynamicsSmall populations in patches • Risk of extinction• 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 andhuman influences -

from the past….

…and from the present

Animals can alter landscape mosaic

…an ecosystemengineer!

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 + near-infrared spectrum (vegetation = bright red)

Remote sensing used to quantifylandscape 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:

• 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 ofLyme 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.

Interveninghabitat (matrix) --->barrier tomovement

***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:

• 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. non-fliers) 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 differentscales.

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