SORTIE-NDSoftware for spatially-explicit simulation of forest dynamics
Growth and Resource-Based Mortality
This behavior calculates probability of survival as a function of growth and some second resource. The identity of the second resource is unimportant and could be anything, from exchangeable calcium levels to soil moisture.
Trees killed by this behavior will have a mortality reason code of "natural".
Parameters for this behavior
How it works
The probability of survival for a tree is calculated with the following equation:
The amount of the second resource is captured in a grid object called Resource. Currently it is up to you to enter a map of the values for this resource grid; for instructions on how to do this, see the Grid Setup Window topic. This behavior does not in any way alter the values in this grid.
The survival probability as calculated above is an annual probability. For multi-year timesteps, the timestep probability is APX, where AP is the annual probability and X is the number of years per timestep. Once a tree's timestep survival probability has been calculated, it is compared to a random number to determine whether the tree lives or dies.
How to apply it
This behavior can be applied to seedlings, saplings, and adults of any species. Any tree species/type combination to which it is applied must also have a growth behavior applied. You must also enter a map of second resource values into the Resource grid.