Software for spatially-explicit simulation of forest dynamics

GMF mortality

GMF mortality is a growth-based mortality behavior.

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

Parameters for this behavior

Parameter nameDescription
Light-Dependent MortalityLight-dependent mortality.
Mortality at Zero GrowthMortality rate at zero growth.

How it works

The GMF mortality model evaluates the following function to determine the probability of a tree's mortality:

m = m1*e-m2G

  • m is the probability of mortality
  • m1 is the Mortality at Zero Growth parameter, for mortality over 2.5 years (see Kobe et al 1995)
  • m2 is the Light-Dependent Mortality parameter, for mortality over 2.5 years (see Kobe et al 1995)
  • G is amount of radial growth, in mm/yr, added to the tree's diameter this timestep

The GMF mortality equation is for a 5 year timestep. The mortality parameters are for a 2.5 year probability of mortality. To calculate the 5 year probability of mortality, SORTIE uses p' = 1 - (1 - p)2. Once the probability of mortality is calculated for a tree, SORTIE generates a random number to which to compare it to determine whether the tree will live or die.

This model was originally described in Kobe et al 1995.

How to apply it

The GMF mortality function assumes a timestep length of five years, so that must be your timestep length in order to use this behavior. 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.