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

Storm direct killer

This behavior kills trees based on storm severity, without an intervening damage step.

Trees removed by this behavior will have a mortality reason code of "storm".

Parameters for this behavior

Parameter nameDescription
Storm Direct Killer - aThe "a" value in the probability of mortality logit function.
Storm Direct Killer - bThe "b" value in the probability of mortality logit function.

How it works

When storms occur, trees to which this behavior are applied have the following probability of mortality:

p

where:

  • p is the tree's probability of mortality, between 0 and 1
  • a is the Storm Direct Killer - a parameter
  • b is the Storm Direct Killer - b parameter
  • D is the storm damage at the tree's location

Once the mortality probability has been calculated, this behavior uses a random number to determine whether it lives or dies. If more than one storm has occurred in the current timestep, each storm gets a separate, independent chance to kill trees.

Trees that die have a "dead" flag set to true and are treated in the rest of the run like trees that have died due to natural mortality.

How to apply it

Apply this behavior to the trees that can be killed in storms. You must also use the Storm disturbance behavior and have any kind of mortality behavior applied to each tree species and life history stage to which this behavior is applied.