Week 5: Landscape Ecology Flashcards
what is landscape ecology?
The study of ecosystems and ecologies across a landscape: encompasses different scales, spatial patterns and management practices
types of fragmented landscape
Natural fragmentation - natural disturbances, soil substrates, lakes, mountain tops, islands
Anthropogenically fragmented landscape - residential development, clear felling, roads, minding
patch vs matrix
Patch: an isolated fragment of habitat
Matrix: landscape surrounding a patch such as grazed fields, urban housing, pine plantation
what are the edge effects?
Configuration: reduced habitat area, increased habitat edge, increased habitat isolation
Abiotic: increased sunlight at edges, changes in water flow, increased wind exposure
Biotic: reduced gene flow, small populations (stochasticity), invasion by weeds and exotic predators, increased competition, changes in pollination rates, matrix subsidy
Anthropogenic: increased hunting, resource gathering, dog and cat predation, grazing
define edge effect. what shapes can they be?
Edge effect: a change in the structure of a habitat at a patch edge
Can be narrow or wide
Narrow edge effects reflect rapid transition
Wide edge effects are called ecotones (transition zones)
Shape of fragment changes the interior to edge ratio
Leopold experiment 1930
1930
Some organisms are edge affiliated
Some birds were more common at forest-field edges
Edges tend to be extremely productive for plant growth and this attracts matrix and patch herbivores and therefore predators
how much species decline and biodiversity loss is due to fragmentation?
How do we separate fragmentation, habitat area and degradation
These effects usually co-occur
Devise large-scale experiments that test apart effects
Meta-analysis
Looked at effect of three aspects of fragmentation: edge effect, reduction in habitat size, isolation
Not highly convincing
Edge can positively or negatively effect species richness
The effect depends on resource flow/distribution between patch and matrix
The relationship between the matrix and the taxa of interest matters
Effect of fragmentation can change over time
should land managers worry about fragmentation?
If we focus on landscape level, then significant negative effects of fragmentation alone are not convincing
Models on patch dynamics imply fragmentation has negative effects
Scaling mechanisms up from patch-scale studies also implies fragmentation alone should have an overall negative effect
Goes back to old SLOSS (single large or several small) argument around reserve design
what is island biogeography?
Attempts to predict species richness on an island based on immigration from mainland and extinction on island
Close to mainland increases immigration
Small islands increases extinction
Helps inform reserve plans - large patches, close together patches
If a catastrophic event hits reserve would populations of species in a landscape be the same? Could there be genetic differences?
what is a meta population?
Set of populations that are linked by movement of individuals between them
inbreeding
Causes extinction in small populations
Fixation of deleterious mutations by genetic drift
Inbreeding depression
evolution of dispersal ability
Butterflies developing higher flight metabolism
Higher fecundity when food is not limited
Poor disperser but good competitor or good disperser but poor competitor
SLOSS debate
Benefits of one large reserve
Lower extinction of the patch
Lower negative edge effects
Can protect species that require large area
Greater species richness within the patch
Lower risk of inbreeding
Benefits of several small reserves
Lower risk of regional extinction
Can cover larger geographic area
Greater regional species diversity
Lower spatial correlation
High metapopulation viability
Maintenance of regional genetic diversity
Best solution depends on
Spatial correlation of the region
Habitat heterogeneity
Minimum viable population size of species
Connectivity among patches
Species traits (dispersal capacity etc.)
Matrix quality
