SORTIE-ND
Software for spatially-explicit simulation of forest dynamics

# Insect Infestation Mortality

This behavior causes mortality in trees that are infested with insects, as determined by the Insect Infestation behavior.

Trees killed by this behavior will have a mortality reason code of "insect".

### Parameters for this behavior

Parameter nameDescription
Insect Mortality - InterceptThe mortality rate, between 0 and 1, at the first timestep of infestation.
Insect Mortality - Max Mortality Rate (0-1)Maximum mortality rate, between 0 and 1.
Insect Mortality - X0The time at which 0.5 of the maximum mortality rate occurs.
Insect Mortality - XbParameter controlling the steepness of the rise of the mortality rate.

### How it works

The mortality rate of trees as a function of time infested is as follows:

where:

• P is the mortality rate, between 0 and 1.
• I is the Insect Mortality - Intercept parameter, as a value between 0 and 1. This is the function intercept, or the mortality rate at the first timestep of infestation.
• Max is the Insect Mortality - Max Mortality Rate (0-1) parameter, as a value between 0 and 1. This is the maximum mortality rate that will occur regardless of how long a tree has been infested.
• T is the time, in years, that an individual has been infested.
• X0 is the Insect Mortality - X0 parameter. This is the time at which half of the maximum mortality rate is reached.
• Xb is the Insect Mortality - Xb parameter. This controls the steepness of the rise of the curve.

Once the mortality rate for an infested individual has been determined, a random number determines whether it will live or die.

The Insect Infestation behavior decides which trees become infested, and tracks the amount of time each individual has been infested.

### How to apply it

Apply this behavior to saplings and/or adults of any species. Any tree to which this behavior is applied must also have the Insect Infestation behavior applied.