Random browse

This behavior simulates random browsing from herbivores.

Parameters for this behavior

Parameter name	Description
Random Browse - Annual Browse Probability (0-1)	The annual probability, from 0 to 1, of being browsed. This is the mean probability if the probability is being varied each timestep.
Random Browse - Probability PDF	The PDF used to vary the browse probability. "None" means the same probability is always used. "Normal" means that each timestep, for each species, a new probability is drawn from a normal distribution.
Random Browse - Browse Probability Standard Deviation	If the probability is being varied each timestep according to a normal distribution, this is the standard deviation of that distribution. This value is ignored if the probability is not being varied.

How it works

The trees eligible for browsing are those trees to which this behavior is applied. Each species has a probability of browse that is the same for all members of that species. Each timestep, for each eligible tree, a random number is used against its species probability to decide whether the tree is browsed.

The probability of browse for a species can be constant, or it can vary each timestep. If it is constant, the probability of browse is always the value in the Random Browse - Annual Browse Probability (0-1) parameter. If the probability is to vary, a new value is drawn from a random distribution, using the value in Random Browse - Annual Browse Probability (0-1) parameter as the mean and the value in Random Browse - Browse Probability Standard Deviation as the standard deviation. This draw happens once per species per timestep; all individuals of a species always face the same probability of browse in a given timestep.

If the timestep length is more than one year, the annual probability of browse is turned into a timestep probability using TP = 1 - (1 - AP)^N, where TP is the timestep probability of browse, AP is the annual probability, and N is the length of a timestep, in years.

Trees that are chosen as browsed are marked as browsed. This behavior does nothing else to them. Other behaviors, such as growth and mortality, may use this information.

How to apply it

Apply this behavior to any species and type of tree.