LANDSCAPE ECOLOGY
SREM 3011
LECTURE 8
Dr Brendan Mackey
Department of Geography
The Australian National University
‘Scale’ - key concept for unifying landscape ecology
- integral component of scientific method of
inquiry
1,Different notions of scale
2,Scale dependent /independent biological and
environmental attributes and concepts
3,Ecological hierarchy theory
4,Implications for spatial landscape ecology models
‘A Unified Theory of Ecology’
Allen & Hoekstra
Different notions or dimensions of scale:
1,Cartographic scale
2,Space & time
3,Grain
4,Extent
5,Resolution
6,Scale-dependency
7,Landscape texture
1,1 000 000,1,20 000 000
1,5 000
1,10 000
Large scale - big + slow
Small scale - small + fast
Typical organization of a GIS database in a land management organization; the
primary division is on the basis of scale,subsequent divisions are into theme
and location,Numerous scale-dependent applications and administrative proce-
dures,such as ensuring a common boundaries where appropriate,mean that
scale must be the primary organizational basis,
Scale has two dimensions:
1,Space and 2,Time
Therefore,large scale phenomena are generally spatially
big and change slowly
Small scale phenomena are generally spatially little and
change quickly
Large scale = low frequency
Small scale = high frequency
eg,Fire regime experienced by a forest (‘rate of return’)
Grain = smallest unit of observation and measurement
= smallest and most ephemeral entities that can
be found in the data
Eg,Microscope Unicellular algae
1m x 1m pit Soil survey
20m x 20m plot Vegetation survey
1 ha plot Vertebrate survey
Grain = ‘Filter’
- human primary senses
- minimum unit of measurement;
size of measuring ‘rod’
A simulated inventory of forest cover undertaken at several scales,A:Hypothetical tree locations and crown
extents; crowns are considered to be impermeable,B to F,the results of an inventory carried out with grain-size
determined by a disc of diameter equal to the vertical bar at the bottom right of each window,For each
location on the grid,the percent of the disc area within crowns is calculated,The cell is classified as ‘forest’
if this mean exceeds 40%,As grain size increased,the inventory results change substantially.At grain size
F,the inventory is clearly missing features which one feels are important,but at grain size B,the concept of
‘forest’ is not being addressed; small intervals between trees are clearly part of the forest,If grain-size was
increased beyond F,the entire area would be determined as forest,despite the fact that only 50% of the
area is occupied by tree crowns,
A B C
D E F
.
Grain - sets lower limit to what we observe
Extent - sets larger limits to which observations or
study apply
the extent of a study has to be bigger than the size of
the object/phenomena
boundary definition influences spatial analyses
fine grain often (but not always) means narrow extent
Resolution = spatial unit to which data are geo-
referenced
raster data (eg,DEM),Resolution = Grid spacing
remote-sensing,Grain = Resolution = Pixel
Size = Grid spacing
Extent,grain and resolution,Possible alternative measures of scale,A,the extent is the interval
of observation,which determines the largest scale observable; B,the grain is the fineness of obser-
vation,which determines the smallest scale observable,C,the resolution is often equated with the
grain,but clearly,this can be misleading as the resolution can be finer than the grain.
Extent
Grain
Resolution
Resolution Grid spacing
Larger
Smaller
Scale Dependency
A,Many phenomena require a particular scale of
perception to make them appear in a certain way
Body form is scale-dependent
Organism is a scale-independent concept
B,The importance of processes (ie,their ecological
significance) varies with scale
Eg,Gravity vs water tension
Evaporation
BUT
Both fleas and elephants are organisms,but their different sizes demand observation
from very different distances,Note that the organizational form is very different with
change of size,even though there is a head and body and legs in both cases,Those
differences relate to scale.
Micro-scale heterogeneity in a flask of unicellular algae (based on Allen
1977),Although the flask appears well mixed to the human observer,at
micro-scale,rapid resource depletion around the cells may mean that
the nutrient levels experience at the scale of the model (cell scale) are
substantially different to the levels observed at the scale of data capture
or human observation (flask-scale).
SREM 3011
LECTURE 8
Dr Brendan Mackey
Department of Geography
The Australian National University
‘Scale’ - key concept for unifying landscape ecology
- integral component of scientific method of
inquiry
1,Different notions of scale
2,Scale dependent /independent biological and
environmental attributes and concepts
3,Ecological hierarchy theory
4,Implications for spatial landscape ecology models
‘A Unified Theory of Ecology’
Allen & Hoekstra
Different notions or dimensions of scale:
1,Cartographic scale
2,Space & time
3,Grain
4,Extent
5,Resolution
6,Scale-dependency
7,Landscape texture
1,1 000 000,1,20 000 000
1,5 000
1,10 000
Large scale - big + slow
Small scale - small + fast
Typical organization of a GIS database in a land management organization; the
primary division is on the basis of scale,subsequent divisions are into theme
and location,Numerous scale-dependent applications and administrative proce-
dures,such as ensuring a common boundaries where appropriate,mean that
scale must be the primary organizational basis,
Scale has two dimensions:
1,Space and 2,Time
Therefore,large scale phenomena are generally spatially
big and change slowly
Small scale phenomena are generally spatially little and
change quickly
Large scale = low frequency
Small scale = high frequency
eg,Fire regime experienced by a forest (‘rate of return’)
Grain = smallest unit of observation and measurement
= smallest and most ephemeral entities that can
be found in the data
Eg,Microscope Unicellular algae
1m x 1m pit Soil survey
20m x 20m plot Vegetation survey
1 ha plot Vertebrate survey
Grain = ‘Filter’
- human primary senses
- minimum unit of measurement;
size of measuring ‘rod’
A simulated inventory of forest cover undertaken at several scales,A:Hypothetical tree locations and crown
extents; crowns are considered to be impermeable,B to F,the results of an inventory carried out with grain-size
determined by a disc of diameter equal to the vertical bar at the bottom right of each window,For each
location on the grid,the percent of the disc area within crowns is calculated,The cell is classified as ‘forest’
if this mean exceeds 40%,As grain size increased,the inventory results change substantially.At grain size
F,the inventory is clearly missing features which one feels are important,but at grain size B,the concept of
‘forest’ is not being addressed; small intervals between trees are clearly part of the forest,If grain-size was
increased beyond F,the entire area would be determined as forest,despite the fact that only 50% of the
area is occupied by tree crowns,
A B C
D E F
.
Grain - sets lower limit to what we observe
Extent - sets larger limits to which observations or
study apply
the extent of a study has to be bigger than the size of
the object/phenomena
boundary definition influences spatial analyses
fine grain often (but not always) means narrow extent
Resolution = spatial unit to which data are geo-
referenced
raster data (eg,DEM),Resolution = Grid spacing
remote-sensing,Grain = Resolution = Pixel
Size = Grid spacing
Extent,grain and resolution,Possible alternative measures of scale,A,the extent is the interval
of observation,which determines the largest scale observable; B,the grain is the fineness of obser-
vation,which determines the smallest scale observable,C,the resolution is often equated with the
grain,but clearly,this can be misleading as the resolution can be finer than the grain.
Extent
Grain
Resolution
Resolution Grid spacing
Larger
Smaller
Scale Dependency
A,Many phenomena require a particular scale of
perception to make them appear in a certain way
Body form is scale-dependent
Organism is a scale-independent concept
B,The importance of processes (ie,their ecological
significance) varies with scale
Eg,Gravity vs water tension
Evaporation
BUT
Both fleas and elephants are organisms,but their different sizes demand observation
from very different distances,Note that the organizational form is very different with
change of size,even though there is a head and body and legs in both cases,Those
differences relate to scale.
Micro-scale heterogeneity in a flask of unicellular algae (based on Allen
1977),Although the flask appears well mixed to the human observer,at
micro-scale,rapid resource depletion around the cells may mean that
the nutrient levels experience at the scale of the model (cell scale) are
substantially different to the levels observed at the scale of data capture
or human observation (flask-scale).
