Landscape ecology methodsAn overview of a few of the methods used in landscape ecology studies

Commonly used methods Some of the more commonly used methods include:

Markov analysis Simulation models Spatially-explicit population models New indices (e.g., green edge)

Markov analysis 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.

Markov analysisThe 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 384.30.841

3.10.007

13.60.036

50.60.111

5.40.012

00

457.01

Man-made hardwoods 1.50.017

48.30.563

1.40.016

34.60.403

00

00

85.71

Mixed forest 2.50.121

0.40.019

13.40.008

4.30.208

0.020.001

00

20.61

Natural hardwoods 35.10.119

60.90.034

13.970.008

1688.00.936

4.10.002

1.580.001

1803.71

Bare lands 1.00.051

00

00

13.70.727

4.20.222

00

18.91

Cut areas 12.250.248

14.650.297

10.40.211

11.70.237

0.40.007

00

49.41

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

Simulation models 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.

Simulation models: Harvest

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.

Harvest

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 population models

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).

Northern Spotted Owl One common use of SEPMs has been in the study of individual and population responses 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?

Northern Spotted Owl 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.

Northern Spotted Owl

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 (USDA 1992).

Landuse change in DublinThis 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.

http://moland.jrc.it/technical_tools/frag/moland_fra.htm

Nature-deficit disorder

Explore 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.