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Lecture 23

Biology 2483A Lecture Notes - Lecture 23: Old-Growth Forest, Passenger Pigeon, Landscape Ecology

Course Code
BIOL 2483A
Sheila Macfie

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Bio 2483 Lecture 23- Landscape ecology and ecosystem management
Key concepts
1. Landscape ecology examines spatial patterns and their relationship to ecological processes.
2. Habitat loss & fragmentation decrease habitat area, isolate pops, & alter conditions at habitat edges
3. Biodiversity can best be sustained by large reserves connected across the landscape and buffered from
areas of intense human use.
4. Ecosystem management is a collaborative process with the maintenance of long-term ecological integrity
as its core value.
1. Landscape ecology examines spatial patterns and their relationship to ecological processes.
Loss and Fragmentation of US Old growth forest
o decrease of passenger pigeon correlated to disappearance of oldgrowth forest
o continuous large patch of oldgrowth forest and then it becomes largely fragmented
Landscape: area in which at least 1 element is spatially heterogeneous; often includes multiple ecosystem
o Heterogeneity may involve different types of landscape elements, and how they are arranged.
o A mosaic is a composite of heterogeneous elements.
Landscape ecologists look at the spatial arrangement of landscape elements: forest patches, soil types,
lakes, etc., across Earth’s surface.
o These patterns influence what species live in an area and the dynamics of ecological processes.
Landscape Composition and Structure
o can see variation in how heterogenous this landscape is
o 5 age classes patchy enviro
o susceptible to fire, it has a thin bark, but it needs fire bc it opens seeds/cone for germination
Habitat patches vary in terms of habitat quality and resource availability.
Patch boundaries, connections between patches, and the matrix between patches can also affect
population dynamics.
have to consider the species you’re looking at
e.g., boreal frog, requires aquatic habitat to lay eggs in and that are predator free of fishes
e.g., wolves, like passenger pigeon, were hunted to extinction in US, not necessarily for food though
case study in tb: how they reintroduce wolves into yellowstone?
o 60-200 wolves in the park, can potentially lead to extinction

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2. Habitat loss & fragmentation decrease habitat area, isolate pops, & alter conditions at habitat edges
Fragmentation results in increasing degradation and edge effects.
Fragmentation results in spatial isolation of populations, making them vulnerable to the
problems of small populations.
When habitat is fragmented, some species go extinct in many of the fragments.
There may be inadequate resources, disruption of mutualisms, or not enough range for foraging.
But some species flourish under the changed conditions.
Fragmentation often leads to loss of top predators, giving rise to cascading effects.
Example: In the Hudson River valley, forest fragments < 2 hectares have very high populations of
white-footed mice; there are no predators and few competitors.
White-footed mice carry the bacterium that causes Lyme disease, and ticks are the vector.
Ticks collected in small forest fragments are much more likely to carry the bacterium than in
large fragments.
The outcome: increased risk of human disease, ultimately a result of habitat fragmentation.
white footed mice are considered reservoirs
ticks in that area had high concentration of bacteria in small fragmented area
Edges (total length of habitat boundary) increase as fragmentation increases.
Edge effects are biotic and abiotic changes associated with this boundary.
The physical environment changes over a certain distance into the fragment, and thus biological
interactions and ecological processes change as well.
when you fragment ecosystems, you get more edges
forests are good at blocking strong wind
- so if in a storm you go into a forest
penetrates further and further into the forest
soil moisture?
-evaporation pulls out moisture/water from soil
solar radiation?
-will increase and will
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