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ecosimple

by Ryan Kelly (Submitted: 11/01/2010)

[screen shot]

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(You can also run this model in your browser, but we don't recommend it; details here.)

WHAT IS IT?

EcoSimple is an ecosystem model in which climate and interactive ecosystem processes dictate the relative abundance of biome types.

HOW IT WORKS

There are four biomes in this version of EcoSimple: tundra, boreal forest, grassland, and deciduous forest. Each biome has limits on the climate it can tolerate (for example, tundra can't grow if it gets too warm), and if an ecosystem pixel is outside of these limits too long, it will die. Pixels can also die if they are burned by wildfire, which is more likely in some biome types than others. Probability of fire increases with age (to simulate increasing fuel load), and fires can be prevented to simulate fire suppression by human beings. Dead pixels regrow into an appropriate ecosystem type based on climate. Finally, the grassland biome is special in that it will tend to turn into a forest after several years if no fire occurs.

HOW TO USE IT

Press 'Setup' to initialize the landscape, and 'Go' to run the model continuously (rate can be adjusted using the speed slider at top). You can also use the 'Step one year' button to run the model one year at a time.

Climate is controlled by the Temperature ('T') and Precipitation ('P') sliders. In addition, 'Climate_Variability' can be turned on or off. When it is off, every pixel has exactly the climate prescribed by the 'T' and 'P' sliders. When 'Climate_Variability' is on, the climate of individual pixels is somewhat random, such that the average climate of the landscape will correspond to user 'T' and 'P' settings, but different biome types will occur in different pixels.

Fire occurs at random as long as 'Suppress_Fire' is turned off, with probability of fire depending on ecosystem type and age. You can also force an ignition at a particular point by clicking there.

SOME RECOMMENDED SCENARIOS TO SIMULATE

a) Arctic warming (T = 2.0C; P = 50 cm; Suppress_Fire = OFF; Climate_Variability = ON)
- The arctic is expected to warm ~5C by 2100 AD. Starting with the typical boreal climate defined above, gradually increase temperature by 5C over roughly 100 years.

b) Fire Suppression (T = 2.0C; P = 50 cm; Suppress_Fire = OFF; Climate_Variability = ON)
- These days, humans manage many natural wildfires to protect property and to achieve desired ecological results. One important consideration for fire managers is that forests tend to become more flammable as they age, due to the accumulation of dead fuel wood. Let the model spin up, then turn fire suppression off for about 50 years, then let a fire start. You may need to slow down the model (slider at top) or run it one step at a time (unclick GO to pause, then use step one year button).

c) Delicate balance (T = 9.0C; P = 46 cm; Suppress_Fire = OFF; Climate_Variability = ON)
- Ecosystems are not always controlled directy by climate. Observe the prairie-like ecosystem described above for awhile before briefly suppressing all fires (perhaps there were several very rainy years in a row).

EXTENDING THE MODEL

This model could definitely be expanded in some very interesting ways. Try adding new biome types or developing more sophisticated and/or realistic interactions. For instance, EcoSimple currently does not account for seed dispersal or migration, and as a result you might have boreal forest suddenly appear in the middle of a grassland, even though realistically there's no good reason for a spruce cone to have landed there!

CITING THIS MODEL

To refer to this model in academic publications, please use: Kelly, R. (2010). EcoSimple (NetLogo model). Department of Plant Biology, University of Illinois, Urbana, IL.

In other publications, please use: EcoSimple, Copyright 2010 Ryan Kelly. All rights reserved.

ACKNOWLEDGEMENTS

The visual technique for representing fire was borrowed from an existing NetLogo model:

"Fire" Copyright 1997 Uri Wilensky. All rights reserved. See http://ccl.northwestern.edu/netlogo/models/Fire for terms of use.

The model "Fire Ecology" (Copyright 2009 Ryan Kelly, available at http://ccl.northwestern.edu/netlogo/models/community/Fire%20Ecology) served as the precursor for EcoSimple. That model was designed as part of a National Science Foundation GK-12 fellowship, and owes many thanks to Susan Camasta and the 2008-09 Hinsdale South AP Environmental Science classes for testing and evaluation.

QUESTIONS AND COMMENTS

Please send questions and comments to: rkelly AT life DOT illinois DOT edu

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