Landscape Ecology
Neutral models of landscape heterogeneity
Terms/people: neutral landscape model (NLM) Caswell 1976 Stauffer 1985 neighborhood (movement) rules hierarchical structure in contagion (H)
Why are models used so frequently in landscape ecology?
Neutral landscape models (NLMs) –
A couple of examples: Fahrig (1997) –
Fahrig (2001) –
With and King (1997) have determined that NLMs in LE have been used for two main purposes: (1)
(2) Origin of NLMs:
Caswell 1976 –
Stauffer 1985 –
How to construct an NLM:
Many software packages can be used to create an NLM (e.g. QRULE); you can even create one in Excel! You will build and use NLMs in lab.
Neighborhood rules (movement rules) – Properties of NLMs:
What should happen to the number of patches on the landscape as p approaches 1.0?
NLMs can also be built to reflect hierarchical structure in contagion (H), which represents changes in pattern with changes in scale. Hierarchical structure has the same or similar pattern at different scales (e.g. fractals). Hierarchical structure is built into an NLM using a recursive procedure (one that references itself at different levels of resolution). Click here for an example of a hierarchical NLM, and here for three examples of different NLMs. Adding contagion in an NLM can be accomplished in various ways. Adding contagion usually results in an NLM that appears more “natural” or “realistic” than a purely random one.
Things to remember about NLMs:
What does it mean when your real landscape is different from an NLM?
What does it mean when your real landscape is NOT different from an NLM?
A single NLM is not particularly useful. Why not? Why do you need to generate multiple NLMs for a given value of p?
What kinds of tradeoffs are invoked with NLMs? NLMs have especially been used to examine how spatial patterning affects the flows of materials (e.g. seed dispersal, gene flow, animal movement) by providing a null template upon which to compare real flows. This is the topic of an upcoming lecture (percolation). And they have been used to document existence of critical thresholds (tipping points), which will also be part of the upcoming lecture on percolation. See Hagen-Zanker and Lajoie (2008) for other examples. Uses of NLMs will be the topic of the next lecture.
References:
Botkin, D.B. 1993. Forest Dynamics: An Ecological Model. Oxford University Press, Oxford.
Cale, W.G., R.V. O'Neill, and H.H. Shugart. 1983. Development and application of desirable ecological models. Ecol. Modelling 18:171-186.
Caswell, H. 1976. Community structure: a neutral model analysis. Ecol. Monogr. 46:327- 354.
Costanza, R. 1989. Model goodness of fit: a multiple resolution procedure. Ecol. Modelling 47:199-215.
Fahrig, L. 1997. Relative effects of habitat loss and fragmentation on species extinction. J. Wildl. Manage. 61:603-610.
Fahrig, L. 2001. How much habitat is enough? Biol. Conserv. 100:65-74.
Gardner, R.H., B.T. Milne, M.G. Turner, and R.V. O'Neill. 1987. Neutral models for the analysis of broad-scale landscape pattern. Landscape Ecol. 1:19-28.
Gardner, R. H. and D. L. Urban. 2007. Neutral models for testing landscape hypotheses. Landscape Ecol. 22:15-29.
Hagen-Zanker, A., and G. Lajoie. 2008. Neutral models of landscape change as benchmarks in the assessment of model performance. Landscape and Urban Planning 86:284-296.
Haefner, J.W. 1996. Modeling Biological Systems: Principles and Applications. Chapman and Hall, New York, NY.
Mankin, J.B., R.V. O'Neill, H.H. Shugart, and B.W. Rust. 1975. The importance of validation in ecosystems analysis. In: New Directions in the Analysis of Ecological Systems, Part 1 (G.S. Innis, ed.). Simulation Councils Proceedings Series, vol. 5. Simulation Councils, La Jolla, CA.
Oreskes, N., K. Shrader-Frechette, and K. Belitz. 1994. Verification, validation, and confirmation of numerical models in the earth sciences. Science 263:641-646. Power, M. 1993. The predictive validation of ecological and environmental models. Ecol. Modelling 68:33-50.
Stauffer, D. 1985. Introduction to Percolation Theory. Taylor and Francis, London.
With, K.A., and A.W. King. 1997. The use and misuse of neutral landscape models in ecology. Oikos 79:219-229.