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
Formation of Terrestrial “Islands”
Habitat Fragmentation • Process of breaking contiguous unit into smaller pieces; area & distance components • Leads to: • Community & Ecosystem processes altered
Patch size #patches Patch isolation 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
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 Insects sampled at 10-m intervals for 100 m
Implications of Changes in Scale 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.
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.