Transcript Introduction to Geog 471

An overview of a few of the methods
used in landscape ecology studies
• Some of the more commonly used methods include:
•
•
•
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Markov analysis
Simulation models
Spatially-explicit population models
New indices (e.g., green edge)
• Markov chain
A random process in which the probability that a certain future
state will occur depends only on the present or immediately
preceding state of the system, and not on the events leading up
to the present state.
The transition matrix and transition probabilities of the observed landscape changes from 1988 to 1996
Transition from row to
column
Man-made
conifers
Man-made
hardwoods
Mixed
forests
Natural
hardwoods
Bare
lands
Cut
areas
1996
total
Man-made conifers
384.3
0.841
3.1
0.007
13.6
0.036
50.6
0.111
5.4
0.012
0
0
457.0
1
Man-made hardwoods
1.5
0.017
48.3
0.563
1.4
0.016
34.6
0.403
0
0
0
0
85.7
1
Mixed forest
2.5
0.121
0.4
0.019
13.4
0.008
4.3
0.208
0.02
0.001
0
0
20.6
1
Natural hardwoods
35.1
0.119
60.9
0.034
13.97
0.008
1688.0
0.936
4.1
0.002
1.58
0.001
1803.7
1
Bare lands
1.0
0.051
0
0
0
0
13.7
0.727
4.2
0.222
0
0
18.9
1
Cut areas
12.25
0.248
14.65
0.297
10.4
0.211
11.7
0.237
0.4
0.007
0
0
49.4
1
1988 total
436.6
127.4
52.7
1802.9
14.1
1.6
2435.3
Integrating landscape models in forest landscape analyses using GIS:
An example from Taiwan
http://www.gisdevelopment.net/aars/acrs/1999/ps1/ps1729.asp
• A computer simulation or a computer model is a computer
program that attempts to simulate an abstract model of a
particular system. Computer simulations have become a useful
part of mathematical modeling of many natural systems in
physics, chemistry and biology, human systems such as
economics, psychology, and the social sciences, and in the
process of engineering new technology, to gain insight into the
operation of those systems.
• Traditionally, the formal modeling of systems has been via a
mathematical model, which attempts to find analytical solutions
to problems that enables the prediction of the behaviour of the
system from a set of parameters and initial conditions.
• HARVEST was designed as a strategic research and
planning tool, allowing assessment of the spatial
pattern consequences of broad timber management
strategies. The model is well suited to evaluate
alternative strategies, providing comparable
predictions about how the alternatives affect the age
(or successional stage) distribution of the forest, the
spatial distribution of forest interior and edge
habitats, and the patch structure of the resulting forest
landscape.
With HARVEST, the object is not to find a scheduling solution
(i.e., determining the order in which individual stands should
be harvested), but to assess the spatial pattern consequences
of general management strategies. HARVEST has been shown
to generate patterns similar to those produced by timber
management (Gustafson and Crow 1999).
• Spatially explicit models have a structure that specifies the
location of each object of interest (organism, population,
habitat patch) within a heterogeneous landscape, and
therefore the spatial relations between habitat patches and
other features of the landscape (e.g., landscape
boundaries, corridors, other patches) must be defined.
• Since the spatial layout of the landscape is explicitly
incorporated, the models can be used to indicate how
populations or communities might be affected by changes in
landscape structure, including changes in landscape
composition (the relative or absolute amount of habitat
types or features in a landscape) or landscape
physiognomy (the exact placement of habitat patches and
other features within the landscape) (Dunning et al. 1992).
• One common use of SEPMs has been in the study of
individual and population response to landscape
change.
• How do the risks to persistence of the owl population
vary among five alternative logging schemes during
the transitional period? Do some alternatives have
unacceptably high risks of crossing a habitat
threshold, beyond which the population declines
inescapably to extinction?
• Questions such as these can be addressed only by considering
the amount, geometry, and rate of change of habitat in a
spatially and temporally explicit fashion. The transient behavior
of the Spotted Owl population in Oregon was examined using
OWL, a SEPM integrated with a GIS of the forested landscape
in Oregon (McKelvey et al. 1992, Turner et al. 1995).
• Preliminary studies indicate that whatever management
strategies are selected will significantly affect the population
trajectory during the transition until the final reserve design is
reached.
• Projected change in the amount of
Spotted Owl habitat on National
Forests for five alternative
strategies (numbered solid lines)
that establish a Spotted Owl
reserve design in the Pacific
Northwest (USDA 1992). The
dashed line indicates the current
amount of owl habitat. Note that
alternatives 3-5 project a
continuing loss of habitat during
part or all of the simulated time
span. This loss occurs even though
the owl is currently listed as
threatened due to past loss and
fragmentation of its habitat (USDI
1992).
This index (Green Edge)
shows how much of a
region’s urban fabric is
adjacent to (i.e. has an
edge with) vegetated
areas. Areas with a high
value for the index will
have greater access to
recreational facilities
(e.g. gardens, parks,
wooded areas, sports
fields), and will be less
affected by noise and air
pollution from traffic.
Nature-deficit disorder
http://moland.jrc.it/technical_tools/frag/moland_fra.htm
• These are a few of the different methods that are used in
landscape ecology (and in crime analysis and medical
geography as well).
• In the papers you review you are likely to come across other
methods—the ability to map the results of analyses has added
considerably to the utility of many methods.