introduction – landscape ecology

Introduction – Landscape Ecology

• Landscape Ecology: Study of landscape structure and processes.– Landscape: Heterogeneous area composed of

several ecosystems.– Landscape Elements: Visually distinctive

patches in an ecosystem.

Human Land Use Practices

Ecosystem simplification:

Intensive Agriculture&

Clean Farming

Timber Extraction&

Fragmentation

Roads: Formation of Barriers in Landscapes

Formation of Terrestrial “Islands”

Habitat Fragmentation • Process of breaking contiguous unit into

smaller pieces; area & distance components

• Leads to:

• Community & Ecosystem processes altered

#patches

Patch isolation

Patch size

Edge

Habitat Fragmentation • area-sensitive species: species that

require minimum patch size for daily life requirements

• Edge effects: influence of factors from outside of a patch

Increased Edge Habitat

Increased Edge Habitat

Edge Effects • Habitat surrounding a patch can:

- change abiotic conditions; e.g., temp.

- change biotic interactions, e.g., predation

Example of nest predation = edge effect of approximately 50 m into forest patch

Habitat Fragmentation • First-Order Effects: fragmentation leads

to change in a species’ abundance and/or distribution

Habitat Fragmentation • Higher-Order Effects: fragmentation

indirectly leads to change in a species abundance and/or distribution via altered species interactions

Habitat Fragmentation: Species-Specific Sensitivity?

• Rare species = more vulnerable

• Wide ranging species = large-area requirements

• Species with reduced mobility = more vulnerable

• Species with low fecundity (related to rarity?)

• Species with short life cycle (or multi-stage life cycle?)

Habitat Fragmentation: Species-Specific Sensitivity?

• Interior-dependent species

• Species vulnerable to human exploitation or disturbance

• Specialist species?

Implications of Changes in Scale

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PredatorPrey

Insects sampled at 10-m intervals for 100 m

Implications of Changes in Scale

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PredatorPrey

Insects sampled at 2000-m intervals for 20,000 m

Landscape Processes

• Landscape structure influences processes such as the flow of energy, materials, and species between the ecosystem within a landscape.

Landscape Structure and Dispersal of Small Mammals

Habitat Patch Size and Isolation and Density of Butterfly

Populations

Introduction – Geographical Ecology

• MacArthur defined geographical ecology as search for patterns of plant and animal life that can be put on a map.– Above level of landscape ecology

Island Area and Species Richness

Species-Area Relationship

Island Biogeography

• equilibrium model suggesting number of species occurring on an island represents a balance between immigration (in) and extinction (out)

• Robert MacArthur & E.O. Wilson

Equilibrium Model of Island Biogeography

• Proposed rates of extinction on islands would be determined mainly by island size.– LG near islands will support highest number.– SM far islands will support lowest number.– SM near and LG far will support intermediate number.