Scale

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• Scale
• What is scale?
• Why is scale important in landscape ecology?
• What are the correct scales to use?
• Scaling
• UP bottom-up approach
• Down top-down approach
• A few rules in scaling
• How to study scalar structure?
• Reading Chapter 2

Common usage of scale
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Definition
Scale is the spatial or temporal domain of an
object or process. In general, the scales of
structures/patterns we see and scales of the
processes that create or maintain them are
positively correlated but this is not always the
case. Scale is characterized by both grain (i.e.,
resolution) and extent Grain smallest unit
of measure about which one has information
Extent Total area (or duration of time) over
which we are considering a phenomenon Grain and
extent set the scale and limit which entities and
cycles may be observed. If we don't see
something, it is merely due to inappropriate
measurement (i.e., poorly chosen grain and
extent). We want to bracket the process or
structure of interest.
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Schematic of two components of spatial scales
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• Why is scale important in landscape ecology?
• Nature of landscape ecology
• Nature and landscapes are organized
  hierarchically. All natural features are scale
  dependent
• Our ability to develop theories of
  pattern-process relationships will be dependent
  on understanding scales of description and scales
  at which relationships naturally occur
• Incorrect coupling between the scale of a pattern
  and the process that creates it limits the
  predictability of future ecological system states
  which, in turn, inhibits development of realistic
  land management plans (a purely applied reason)
• There are also some sampling and statistical
  reasons (e.g., want to sample at a scale that
  ensures independent replicates)

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Scale Processes
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Two predominant views on choosing scales   A few
scales drive ecological functions and,
therefore, we should choose the right scales
(Holling 1991) Example on disturbance regimes of
different scales Natural disturbance regime -
the long-term pattern of frequency, intensity,
spatial extent, internal heterogeneity of
disturbances) A boreal forest has large,
intense, stand-initiating disturbances resulting
in a coarse-grained pattern of relatively young,
even-aged forest whereas Wetter, temperate
rainforests have smaller, less intense
disturbances that kill trees in patches of a
single to a few trees resulting in a
finer-grained mosaic of uneven-aged
patches   Multiple scale analysis is needed
(Levin 1992) The relative importance of
parameters controlling ecological processes
varies with scale, e.g., locally, fire initiation
depends on topographic position, fuel load butat
large spatial scales, frequency and extent of
fire are determined by longer-term weather and
climate   Cumulative effects of stand-level
(i.e., finer scale) management are expressed at
the landscape level. e.g., small patch clearcuts
remove a trivial amount of habitat for
latesuccessional species, but cumulatively, the
population may be threatened by fragmentation of
the watershed   Some local scale activities can
have large-scale impacts. e.g., downstream
effects of small landslide upstream.  
landscape may exhibit critical thresholds at
which ecological processes show qualitative
changes. e.g., disturbance spread controlled by
frequency when habitat area is below threshold
but by intensity when above threshold
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 Rationale for multiple scale approach (cont.)
Multiple life stages or scales of structure may
be required by an organism. e.g., the northern
spotted owl example   Small scale processes can
interact to create bottom-up controls of
landscape-level patterns and processes. e.g.,
fine-scale local edaphic factors result in the
distribution of common stand types and less
common hemlock-hardwood but at the coarse scale,
nearly pure hardwood patches are associated with
disturbances to the matrix (Pastor and Broschart
1990).   large-scale processes can exert
top-down control creating context for finer scale
dynamics. e.g., infrequent, extreme events
(Yellowstone fires) will influence species
distribution and composition for ages   The
bottom line is that the scale of study will
affect conclusions about pattern-process
relates.   Whichever view one espouses, all agree
that to understand ecological phenomena, we must
study them at the inherent scales (or multiple
scales) at which they occur
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• Up Scaling Bottom-up approach
• Begins with individuals or entity based
  measurement and adds appropriate constraints to
  explain the result phenomena at higher levels.
  The objective is to use information that is
  available at finer scales to predict at larger
  scales. The bottom-up approach is necessary
  because of the suite of multiple scales and
  understanding of mechanism causing larger scale
  phenomena. We must to learn how to aggregate and
  simplify, retaining essential information without
  getting bogged down in unnecessary details.
• Examples
• Stand dynamics model (Urban et al.) or early
  succession
• Prediction of carbon storage at global scales
• Predict deer population of a region (e.g.,MW)
• Species richness and diversity of an landscape

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• Down Scaling Top-Down approach
• Use the concept of constraint to predict
  phenomena at finer scales. The objective is to
  identify the constrains that are important at
  each level.
• Examples
• Ecological Land Types in Upper Michigan
• Global climate change GCM Þ Regionalized
  model Þ Local Weather Condition Þ forest
  microclimate
• World's Vegetation
• Landscape dynamics
• Books in libraries subdirectories on your
  computer

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A Few Rules in Scaling Across scales, we can
learn how information is translated. We have to
determine what information is preserved and lost
as one moves from one scale to another.
Predictions based on either approach need clear
identification of parameters (i.e., independent
variables) at different scales. This is because
any processes important at one scale are
frequently not important (or predictive) at other
scales, and different information is often lost
as spatial data are considered at coarse scale of
resolution. Identify an array of scales at
which the study processes can be detected. The
key is study an ecological phenomenon across all
these scales rather than choose a "correct"
scale. In another word, our effort is to detect
patterns occurring at multiple scales.
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How do we study scalar structure?
Quantitative methods such as geostatistics,
wavelet analysis, spectrum analysis, fractal
analysis, and computer simulations explore or
identify scales of pattern (and process).
Leaf viewed from afar
Leaf viewed microscopically Drawings by (Kandis
Elliot)
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Wu Li 2005
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Scale and Scaling in Landscape Ecology