Time-Since-Transition

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The Time-Since-Transition (TST) properties allow users to define how transitions depend on the transition history of a cell. For example, you may want to define a Fuel Buildup pathway that can only occur after a certain amount of time has elapsed since the last Fire has moved through a stand. In the probabilistic transitions property you would set a Min TST value for this pathway that corresponds to the time required without fire for a fuel buildup to occur; in the time-since-transition groups property you would set the Fuel Buildup transition type to depend on the Fire transition group; and in the time-since-transition randomization property you would define the initial time since transition distribution for each cell on your landscape.

Time-Since-Transition Groups

The Time-Since-Transition (TST) Groups property is used to associate a Transition Group with each Transition Type for the calculation of TST dynamics for Probabilistic Transitions. For example setting the Transition Type to “Fuel Buildup” and the TST Group to “All Fire” would indicate that any TST settings for “Fuel Buildup” probabilistic transitions would be contingent upon the time since the transitions in the “All Fire” group.


The fields for the Time-Since-Transition Groups property are:

Primary Stratum (optional)

The primary stratum (Vegetation Type by default) for which the TST Group record applies. If left blank then the TST Group record applies to all primary strata.

Secondary Stratum (optional)

The secondary stratum (Planning Zone by default) for which the TST Group record applies. If left blank then the TST Group record applies to all secondary strata.

Transition Type

The transition type for which a TST group is being associated.

Time-Since-Transition Group

The transition group to be used for the purposes of calculating TST values for the transition type.

Time-Since-Transition Randomization

The Time-Since-Transition (TST) Randomization property is used to initialize the TST values at the start of a model run. This feature randomly assigns a TST value between a Minimum and Maximum Initial TST Value for each Simulation Cell.


The fields for the Time-Since-Transition Randomization property are:

Primary Stratum (optional)

The primary stratum (Vegetation Type by default) for which the TST Randomization record applies. If left blank then the TST Randomization record applies to all primary strata.

Secondary Stratum (optional)

The secondary stratum (Planning Zone by default) for which the TST Randomization record applies. If left blank then the Randomization record applies to all secondary strata.

Transition Group (optional)

The transition group for which initial TST values are being randomized. If left blank, then the Randomization record applies to all transition groups.

State Class (optional)

The state class for which initial TST values are being randomized. If left blank, then the Randomization record applies to all state classes.

Initial TST Min

The minimum value to be assigned as the TST for any Simulation Cells in the Stratum specified.

Initial TST Max

The maximum value to be assigned as the TST for any Simulation Cells in the Stratum specified. Values will be randomized between the min and max.