The occurrence of unplanned fire is a good example of a stochastic disturbance. In some places of the world, fires are very likely to occur, but their exact occurrence is uncertain. The best we can do is make probabilistic predictions. For example, we might be able to estimate that the probability of a particular point in a forest burning within the next year is 0.01 (1 in 100).
In contrast, logging of forests by humans tends to be systematic, occurring at prescribed intervals - the rotation age of the forest.
Stochastic and deterministic disturbance have very different effects on the age of the forest, even when the average time between disturbances is exactly the same. This is illsutrated in the following example.
Last updated 11 November 1999