emergence of landscape ecology
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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
?
?
?
?
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
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
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
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)
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
Ecological Scale
• Scale characterized by:– grain: smallest
spatial resolution of data
e.g., grid cell size, pixel size, quadrat size (resolution)
Fine Coarse
Ecological Scale
• Scale characterized by:– extent: size of
overall study area (scope or domain of the data)
Small Large
Ecological Scaling: Components of Scale
• Minimum Patch Size: min. size considered > resolution of data (defined by grain)– Size of landscape or study
area
Ecological Scaling: Definitions• Ecological scale & cartographic scale are exactly opposite
– Ecological scale = size (extent) of landscape
– Cartographic scale = ratio of map to real distance
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
Scale in Ecology & Geography
• ecological vs. cartographic scale– e.g., map scale
1:24,000 vs. 1:3,000fine vs. coarselarge vs. small extent
1:24,000
1:200,000
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.
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
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
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)
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
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
Scale: Jargon• scale vs. level of organization
Space - Time
Space - Time
Space - Time
Individual
Population
Community
Ecological Scaling: Implications of Scale• As one changes scale, statistical relationships may
change:– Magnitude or sign of correlations– Importance of variables– Variance relationships
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,
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
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
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
Multiscale Analysis
• Species-specific perception of landscape features : scale-dependent
– e.g., mesopredators in Indiana
• Modeling species distributions in fragmented landscapes
Hierarchy Theory
• Lower levels provide mechanistic explanations
• Higher levels provide constraints
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
Constraints (significance)
Level of Focus (level of interest)
Components (explanation)
Constraints
Why are long-tailed weasel populations declining in fragmented landscapes?
Components
Population
Community
Individual
Constraints
Why are long-tailed weasel populations declining
in fragmented landscapes?
Small body sizemobility
Population
Community
Individual
PredatorsCompetitorsPrey dist’n
Why are long-tailed weasel populations declining
in fragmented landscapes?
Components
Population
Community
Individual
Scale & Hierarchy Theory • Change scale:
1) influential variables might not change, but
2) shift in relative importance likely
Example: Predicting rate of decomposition of plant matter
Local scale = lignin content & environ. variability
Global scale = temperature & precip.
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