The forest is modelled as a cellular automaton where each cell has can be in one of two states:
The update procedure is as follows: in each iteration step, iterate over all cells in a random order. For each cell, one of two actions can take place, depending on the current state of the cell:
emptycell becomes a
treeignites with a probability
p_lightningand ignites all cells indirectly connected to it. The cluster burns down instantaneously and all cells transition to state
The new state of a cell is applied directly after it was iterated over, i.e. cell states are updated sequentially.
There is the possibility to introduce heterogeneities into the grid, which are implemented as two additional possible cell states:
- A cell can be a constantly ignited fire
source, instantly burning down a cluster that comes into contact with it.
- A cell can be a
stone, being immune to fire and not taking part in any model dynamics.
These heterogeneities are controlled via the
stones entries of the model configuration, which both make use of the entity selection interface.
The following data is stored alongside the simulation:
kind: the state of each cell. Possible values:
2: (not used)
source, is constantly ignited
stone, does not take part in any interaction
age: the age of each tree, reset after lightning strikes
cluster_id: a number identifying to which cluster a cell belongs;
0for non-tree cells
tree_density: the global tree density
- Per Bak, Kan Chen, and Chao Tang, 1990: A forest-fire model and some thoughts on turbulence, Physics Letters A, 147, (5-6), 297–300, DOI: 10.1016/0375-9601(90)90451-S.
- Barbara Drossel and Franz Schwabl, 1992: Self-organized critical forest-fire model, Physical Review Letters, 69, 1629, DOI: 10.1103/PhysRevLett.69.1629