# Different TSD for different proportions of same disturbance

Syncrosim Forums ST-Sim & State-and-Transition Simulation Models Different TSD for different proportions of same disturbance

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• #20886
Louis_Provencher
Participant

Hi,
We are trying to simplify fire modeling in forested systems (think ponderosa pine). Assume there is only one AllFire disturbance with Replacement, Mixed Severity Fire, and Surface fire entirely replaced by AllFire and proportions. In the current models, TST of 15 years is assigned to Replacement and Mixed Severity Fires conditional on any fire or fuels thinning operation (i.e., will not burn if burned by any fire or thinned in last 15 yeas, including Surface Fire). Surface Fire has a TST of 0 years. Will St-Sim respect different TSTs among proportions of a single disturbance? Thanks. Cheers, Louis Provencher

#20887
leonardo-frid
Keymaster

HI Louis, the answer is yes. The way I would set this up is something like the following using the same disturbance type “All Fire” for all pathways. Note the values used for proportions are just examples.
Destination State Class | TST Min | TST Max | Proportion
[Post Surface Fire] | 0 | 14 | 1.0
[Post Surface Fire] | 15 | [Blank] | 0.5
[Post Mixed Fire] | 15 | [Blank] | 0.2
[Post Replacement Fire] | 15 | [Blank] | 0.3

Note that proportions will be respected amongst rows that meet the TST criteria for a specific cell. Because the 0-14 and > 14 conditions are mutually exclusive, this configuration would work fine. Within 15 years of a disturbance only surface fire is possible. After 15 years all three are possible and proportions add to 1.0.

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