NetLogo User Community Models
## WHAT IS IT?
This model explores the dynamics of an animal/tree/fire ecosystem with random fires.
Our model considers a new element in forest fire modeling, namely the dynamics of a forest animal, intimately linked to the trees. We show that animals and trees react differently to different types of fire. A high probability of fire initiation results in several small fires, which do not allow for a large fuel accumulation and thus the destruction of many trees by fire, but is found to be generally devastating to the animal population at the same time. On the other hand, a low fire initiation probability allows for the accumulation of higher quantities of fuel, which in turn results in larger fires, more devastating to the trees than to the animals. Thus, we suggest that optimal fire management should take into account the relation between fire initiation and its different effects on animals and trees. Further, wildfires are often considered as prime examples for power-law-like frequency distributions, yet there is no agreement on the mechanisms responsible for the observed patterns. Our model suggests that instead of a single unified distribution, a superposition of at least two different distributions can be detected and this suggests multiform mechanisms acting on different scales. None of the discovered distributions are compatible with a power-law hypothesis.
Please cite this Netlogo model as:
## HOW IT WORKS
The model has three hierarchical levels: entities, interactions, and environment, with the first two being modeled explicitly and the environment being modeled implicitly.
Things to Know
Animals can breed, whereby one individual becomes 2 individuals:
Animals die by:
Trees produce seeds:
Trees die by:
Fires are initiated:
Fires die if:
## HOW TO USE IT
1.) Initialize the number of animals, trees, and fires.
## THINGS TO NOTICE
Small fire strength will produce a small number of devastating large fires. This is very detrimental to the trees.
Large fire strength produces many smaller and medium sized fires. This is more devastatiung to the animal populations than to the trees.
The distribution of fires DOES NOT follow a power law (see paper for detailed analysis).
## THINGS TO TRY
Try changing the TreeBreedingPercent and FireStrength parameters. Notice the significant changes in the population graph.
Try finding specific parameters to create a stable ecosystem between the three "breeds" such that none of them become extinct.
The fire strength parameter corresponds to the number of lightning that can initiate fires in the forest.
## EXTENDING THE MODEL
Add extra parameters such as estimating wind speed and direction as well as temperature and movement patterns of the animals, or add the possibility of the animals moving towards the trees rather than moving randomly looking for an appropriate breeding habitat.
## NETLOGO FEATURES
Note the use of breeds to model three different kinds of "turtles": animals, trees, and fires.
Note the use of "if random 100 < AnimalDeathPercent" to determine the percent of animals that die each year.
Also note the random fire strength to signify a random number of fires in a range between the user defined maximal amount and 0. This is much more realistic than a rigidly deterministic number of fires each year.
## RELATED MODELS
Look at "Wolf Sheep Predation" for another model of ecosystem dynamics involving three elements. Also see different forest fire models in the community page, but those mainly focus on 2 components only.
## CREDITS AND REFERENCES
Roland, Byron email@example.com ETSU BISC Johnson City TN USA
Paper based on this program:
Karsai, I., Roland, B. and Kampis, G. 2016: The effect of fire on an abstract forest ecosystem: An agent based study. Ecological Complexity Volume 28, Pages 12–23. http://dx.doi.org/10.1016/j.ecocom.2016.09.001.
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