Probabilistic transitions

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Path-probabilistic-transitions.jpg


Every probabilistic transition pathway in a pathway diagram is characterized according to the following fields:

From Stratum

The stratum associated with the source state class of the probabilistic transition pathway.

From Class

The unique label (e.g. cover type and structural stage) associated with the source state class of the probabilistic transition pathway.

To Stratum

The stratum associated with the destination state class of the probabilistic transition pathway. If blank then assumed to be the same as the From Stratum. Default value (if left blank) is the same as From Stratum

To Class

The unique label (e.g. cover type and structural stage) associated with the destination state class of the probabilistic transition pathway.

Transition Type

The transition type associated with the probabilistic transition pathway.

Prob

The probability that this probabilistic transition pathway will occur each timestep.

Propn

This Proportion field is used to help represent multiple branching pathways associated with a single transition type for a particular source state class. For example, suppose that there is a probability of 0.1 that a "Fire" transition may occur for a particular source state class, and that there are 2 possible pathways out of this class associated with this "Fire" transition type, each occurring 50% of the time. Both pathways can be assigned the same value for the Prob field (i.e. 0.1), and then each pathway is assigned a value of 0.5 for the Propn field. When the model runs, the effective probability is calculated as Prob x Propn. Default value (if left blank) is 1.

Prob x Propn

This is a calculated field that represents the product of the Probability (Prob) and Proportion (Propn) fields, and is the value used by the model for the pathway's probability. The sum of the Prob x Propn values for a particular source state class should never be greater than 1; if they are then the model scales the probabilities downwards.

Age Min

The minimum age for a simulation cell to be eligible for this probabilistic transition pathway. Default value (if left blank) is the minimum age of the state class to which the transition applies.

Age Max

The maximum age for a simulation cell to be eligible for this probabilistic transition pathway. Default value (if left blank) is the maximum age of the state class to which the transition applies.

Age Shift

The relative change in the age of the simulation cell after the transition occurs. For example, if the age of the simulation cell is 50 prior to the transition, and the Age Shift is set to -20 for a probabilistic transition pathway, then the post-transition age of the simulation cell will be 50-20=30. Note that the age of the simulation cell after a transition can never be outside the bounds of the ages for the destination state class. Default value (if left blank) is 0.

Age Reset

If set to Yes then the age of the simulation cell is reset to the minimum age of the destination state class after a transition occurs. For example if the minimum age of the destination state class is 10, and the Age Reset is set to Yes, then the post-transition age of the simulation cell will always be set to 10 (regardless of the source state class age). Note that this feature can be used in conjunction with the Age Shift field: so for example if the Age Shift is set +20 for the example above, then the post-transition age of the simulation cell will be 10+20=30. Default value (if left blank) is Yes.

TST Min

The minimum "time-since-transition" value for the simulation cell to be eligible for this probabilistic transition pathway. Default value (if left blank) is 0.

TST Max

The maximum "time-since-transition" value for the simulation cell to be eligible for this probabilistic transition pathway. Default value (if left blank) is 9999.

TST Shift

The relative change in the "time-since-transition" (TST) value of the simulation cell after the transition occurs. For example, if the TST of the simulation cell is 40 prior to the transition, and the TST Shift is set to -20 for a probabilistic transition pathway, then the post-transition TST of the simulation cell will be 40-20=20. Note that the TST of the simulation cell after a transition can never be less than 0. Default value (if left blank) is -9999.