species-of-the-week wood duck (aix sponsa). brink of extinction by early 1900’s, culminative...
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Species-of-the-Week
Wood Duck (Aix sponsa)
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Brink of Extinction
By early 1900’s, culminative effects of:
1) wetland drainage (ag. expansion)
2) deforestation
3) overhunting
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Habitat
• Wooded swamps & river bottomlands
• Natural tree cavities for nesting (cypress, sycamore, silver maple, black ash)
• Home range changes with flooding events
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Food
* In water <18”, feed on:
- seeds of trees (e.g., acorns)
- also field grains
* Young = aquatic insects
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Reproduction
Pairing in late Oct into spring (Mar-July nest)
Clutch size = 6-10 eggs
Behavior
- Dump nests (up to 30+ eggs in 1 nest) = “egg dumping” behavior = intraspecific brood parasitism
- may decrease hatch rates to 10%
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Factors Determining Patterns of Habitat Use
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Concept of Habitat Selection
• Wildlife perceiving correct configuration of habitat needed for survival – differences based on age/experience/chance? –
• Niche concept
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Concept of Habitat Selection
• Hutchison = n-dimensional hypervolume as explanation of the niche
• Fundamental vs. Realized Niche
Species 1Species 2
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Testing the Hutchinsonian Niche Concept of Habitat Selection• James – work with birds in Arkansas…
quantified habitat relationships
• How do birds select habitat?• niche gestalt :
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Wildlife Habitat Ecology & Mgt
• Habitat from an evolutionary perspective• Species distribution relative to habitat dist’n• Climatic events
• Pleistocene Epoch & dist’n of modern species
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habitat interspersion –
Leopold’s Law of Interspersion
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Habitat Fragmentation
1) gap formation
2) decrease patch size
3) increase isolation
4) increase edge
5) conversion of matrix
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Concepts• Habitat = species-specific resources
available (relative quality)
• Habitat Use = manner in which species use resources
• Habitat Selection = hierarchical decision process (innate & learned) of what habitats to use
• Habitat Preference = based on selection of habitat, which are used more than others (preferred vs. avoided)
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Concepts• Habitat Availability = accessibility of
resources
• Habitat Quality = positive relation with fitness (not just density)
• Critical Habitat = resources essential to the species….ESA designation….
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Scale Dependence of Habitat Selection
1st Order2nd Order3rd Order4th Order
Macrohabitatvs.
Microhabitat
1st order – innate?
2nd order –decisions
3rd &4th order –decisions
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Guild Concept• guild = group of species that exploit the
same class of resources in similar way• community guild = no taxonomic
restrictions; guild members chosen based on investigator-defined resources
• assemblage guild = guild members based on taxonomic relations
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Models of Habitat Relationships• Model (assess) habitat for wildlife
species, e.g., USFWS
• Habitat Suitability Index (HSI) models
- include top 3 environmental variables related to a species’ presence, distribution, & abundance
HSI = (V1 x V2 x V3)1/3 = 0 to 1
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• Yellow Warbler HSI
for different forest conditions
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HSI models• useful for representing possible major
habitat factors
• true value as hypotheses
• Do not provide information on:
- population size or trend
- behavioral responses
• single-species approach
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Emergence of Landscape Ecology
Equilibrium View
• Constant species composition
• Disturbance & succession = subordinate factors
• Ecosystems self-contained• Internal dynamics shape
trajectory• No need to look outside
boundaries to understand ecosystem dynamics
Structure
Function
?
?
?
?
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Emergence of Landscape Ecology
Dynamic View
• Disturbance & ecosystem response = key factors
• Disturbance counter equilibrium
• Ecosystems NOT self-contained
• Multiple scales of processes, outside & inside
• Essential to examine spatial & temporal context
Structure
Function
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Scale• What’s the big deal?
• Seminal pubs– Allen & Starr (1982) – Hierarchy: perspectives
for ecological complexity– Delcourt et al. (1983) – Quaternary Science
Review 1:153-175– O’Neill et al. (1986) – A hierarchical concept
of ecosystems
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Ecological Scaling: Scale & Pattern
• Acts in the “ecological theatre (Hutchinson 1965) are played out across various scales of space & time
• To understand these dramas, one must select the appropriate scale
Tem
pora
l Sca
le
Spatial ScaleFine
Sho
rt
Coarse
Lon
g
Recruitment
Treefalls
Windthrow
Secondary Succession
Species Migrations
SpeciationExtinction
Fire
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Ecological Scaling: Scale & Pattern• Different patterns emerge, depending
on the scale of investigation
Am
eric
an R
edst
art
Least Flycatcher
Am
eric
an R
edst
art
Least Flycatcher
Local Scale(4 ha plots)
Regional Scale(thousands of ha)
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Ecological Scaling: Components of Scale
• Grain: minimum resolution of the data– Cell size (raster data)
– Min. polygon size (vector data)
• Extent: scope or domain of the data– Size of landscape or
study area
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Ecological Scale
• Scale characterized by:– grain: smallest
spatial resolution of data
e.g., grid cell size, pixel size, quadrat size (resolution)
Fine Coarse
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Ecological Scale
• Scale characterized by:– extent: size of
overall study area (scope or domain of the data)
Small Large
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Ecological Scaling: Components of Scale
• Minimum Patch Size: min. size considered > resolution of data (defined by grain)
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Ecological Scaling: Definitions• Ecological scale & cartographic scale are exactly opposite
– Ecological scale = size (extent) of landscape
– Cartographic scale = ratio of map to real distance
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Scale in Ecology & Geography
• ecological vs. cartographic scale
Ecology Geography
Small
(Fine)
Fine resolution
Small Extent
Coarse resolution
Large Extent
Large
(Broad)
Coarse resolution
Large extent
Fine resolution
Small extent
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Scale in Ecology & Geography
• ecological vs. cartographic scale– e.g., map scale
1:24,000 vs. 1:3,000fine vs. coarselarge vs. small extent
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1:24,000
1:200,000
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Ecological Scaling: Components of Scale
• Grain and extent are correlated
• Information content often correlated with grain
• Grain and extent set lower and upper limits of resolution in the data, respectively.
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Ecological Scaling: Components of Scale
• From an organism-centered perspective, grain and extent may be defined as the degree of acuity of a stationary organism with respect to short- and long-range perceptual ability
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Ecological Scaling: Components of Scale
• Grain = finest component of environment that can be differentiated up close
• Extent = range at which a relevant object can be distinguished from a fixed vantage point
Fine CoarseScale
ExtentGrain
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Ecological Scaling: Components of Scale• From an anthropocentric
perspective, grain and extent may be defined on the basis of management objectives
• Grain = finest unit of mgt (e.g., stand)
• Extent = total area under management (e.g., forest)
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Ecological Scaling: Components of Scale• In practice, grain and extent often dictated by scale of
available spatial data (e.g., imagery), logistics, or technical capabilities
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Ecological Scaling: Components of Scale• Critical that grain and extent be defined for a study and
represent ecological phenomenon or organism studied.• Otherwise, patterns detected have little meaning and/or
conclusions could be wrong
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Scale: Jargon• scale vs. level of organization
Space - Time
Space - Time
Space - Time
Individual
Population
Community
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Ecological Scaling: Implications of Scale• As one changes scale, statistical relationships may
change:– Magnitude or sign of correlations– Importance of variables– Variance relationships
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Implications of Changes in Scale
• Processes and/or patterns may change• Hierarchy theory = structural
understanding of scale-dependent phenomena
ExampleAbundance of forest insects sampled at different distance Intervals in leaf litter,
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Implications of Changes in Scale
0
5
10
15
20
25
30
35
40
45
PredatorPrey
Insects sampled at 10-m intervals for 100 m
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Implications of Changes in Scale
0
5
10
15
20
25
30
35
40
45
PredatorPrey
Insects sampled at 2000-m intervals for 20,000 m
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Identifying the “Right” Scale(s)
• No clear algorithm for defining
• Autocorrelation & Independence • Life history correlates
• Dependent on objectives and organisms
• Multiscale analysis!
• e.g., Australian leadbeater’s possum
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Multiscale Analysis
• Species-specific perception of landscape features : scale-dependent
– e.g., mesopredators in Indiana
• Modeling species distributions in fragmented landscapes
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Hierarchy Theory
• Lower levels provide mechanistic explanations
• Higher levels provide constraints
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Scale & Hierarchy Theory
• Hierarchical structure of systems = helps us explain phenomena
–Why? : next lower level
–So What? : next higher level
• minimum 3 hierarchical levels needed
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Constraints (significance)
Level of Focus (level of interest)
Components (explanation)