Landscape
Ecology
Landscape
Ecology
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Involves multiple populations interacting in
time and space between several different ecosystems.
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“Blinking Lights”
Theory
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Often presented as an application of “Island Biogeography” -- Concentrates on local population/species
extinctions.
Island Biogeography & Landscape Ecology
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When one species goes extinct, it
is replaced so that there’s an
equilibrium
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Replacement species is not
necessarily the same as the extinct population…may be another from the same guild.
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Smaller islands have higher
extinction rates than larger islands.
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Extinction rates increase with
increasing distance between islands
Lesson: Size
AND distance both affect species equilibrium
Lesson: Agroecosystems can fragment landscapes
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Some species are stranded on their islands – increasing the chance that they might go
locally extinct.
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Reduction in biodiversity is good for pests which thrive in the
agroecosystem anyway.
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Note that reduction is in species diversity – includes number of spp. AND number of
individuals.
Green
Network Concept
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Maintain a network of contiguous patches & corridors that are not part of the
agroecosystem.
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Specific Things to do can be found at:
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Enforcement/implementation?
Ecological
Succession
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An orderly, directional and
therefore predictable process of development that involves changes in species
structure and community processes over time.
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Results from a modification of the
physical environment by the community and culminates in a stabilized ecosystem
in which maximum biomass and symbiotic functions are maintained.
Succession Sequence
Fig. 4-1,
p. 69
Implications of Early Succession Systems
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Trophic cycles are disrupted (adds to the biodiversity problem)
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Species good at invasion are favored
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Nutrient cycles are altered, biomass does not accumulate/cycle
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Energy flow is not webbed but, instead, directed toward one commodity
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Ecology “resets”
each cropping season
2. Definitions and Terminology
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Carnivores and Omnivores can be
monophagous, oligophagous, or polyphagous
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Host organisms do not necessarily
host parasites, herbivorous insects also feed on “hosts”
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Note distinction between parasites
and parasitoids. Both can be internal or
external (ectoparasites).
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Add “Pathogen – A
microbial parasite that causes disease. Primary – attacks a healthy host, secondary – attacks an
injured/weakened host.”
3. Trophic Dynamics
Large
subject that is central to pest injury and pest management.
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General Concepts
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Bottom-up versus top-down processes
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Basic food chains –
note the diagrams
– Pathogens
– Weeds
– Webs (generalized and animal-based)
General Concepts of Trophic Dynamics
Top-Down vs Bottom-up Trophic Systems
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Top-Down –
Producers (plants) limit the growth of primary consumers (herbivores) which
limit the growth of primary carnivores & so on.
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Bottom-up –
Top consumers limit growth at the next lowest level throughout the chain.
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Note that “limit” can be an economic effect, not necessarily
an ecological one
Top-Down vs Bottom-Up Trophic System
Grazer vs. Decomposer Systems
Food Webs
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Two or more trophic systems linked within a given ecosystem or
landscape.
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Three main categories in agroecosystems:
–
Animal-based (animal production systems)
–
Above-ground, plant based (Crop Production Systems [CPS])
–
Soil food web in CPS’s
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The two CPS webs interact but are usually managed separately
Limiting Resources & Competition
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Populations can be limited in several ways
–
Food & water
–
Shelter/Reservoir
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Limitation can occur at any stage or time (e.g. overwintering)
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Effectiveness dependent on population
ecology of individual pest. Life history
strategy important part of that ecology.
r- vs.
K-selected pests
Managing for one may help other
Interactions Between Pest
Categories
Read
Chapter 7, Ecosystem Biodiversity & IPM
Interactions Between Pest
Categories
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Trophic Relationships
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Environmental (Habitat)
Modification Result
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Mechanical Effects
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Response to Control Tactics
– Non-pesticide
– Pesticide-related
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“Interactions” may be:
– Pest-pest or pest-crop
– Measured in injury or damage
This subject excludes the direct effects of:
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Interactions within pest categories (i.e. – pathogen – pathogen). But note that viruses, bacteria, fungi, &
nematodes are different “categories” for Norris et al.
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Interactions between pests and their natural enemies
Direct vs. Indirect According to Brown
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Direct:
Pest A
-> Pest B -> Outcome
– Outcome may be biological or economic
– If Spp. A & B are present, outcome is realized
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Indirect:
Pest A
-> Affector -> Pest B -> Outcome
– “Affector” may be another pest, management action,
environmental effect, etc.
– A & B & Affector must all be present for outcome to occur