Using ST-Sim Strata

[katie-birchard]

We recently received the following question regarding ST-Sim usage:

I want to confirm how to run [ST-Sim] non-spatially for three strata (e.g., PVT + Management Area + NF Ranger District). Is it correct that I will have to create separate strata for all combos of these, and then create initial conditions for all states within these joined strata? All of the state classes and transitions will probably be the same for each strata, so would I just copy each model that now exists (only by PVT) 2 times, renaming each by their 3-strata class (e.g., douglas-fir_MA1_RD1, douglas-fir_MA2_RD1, etc). Since we have about 10 PVT models, I’ll end up with 30 in the end? Thanks.

Solution: Instead of creating a single ST-Sim stratum based on all the different possible combinations of the three strata, I would suggest taking advantage of the Primary, Secondary, and Tertiary Stratum fields in the Strata tab of the Project Definitions.

To begin, open the Project Properties and navigate to the Strata tab. On the left-hand side, you can select which stratum you would like to edit.

The Primary Stratum would contain each unique PVT value (example below):

The Secondary Stratum would contain each unique Management Area value (example below):

And the Tertiary Stratum would contain each unique NF Ranger District (example below):

You can integrate these 3 strata into your Initial Conditions by adding the optional Secondary and Tertiary Stratum columns to the datasheet. To do this, open your Scenario Properties, click on the Initial Conditions tab, then right-click in the Distribution table (lower half of the window) to bring up the context menu. Click on Secondary Stratum and Tertiary Stratum to add them to the Initial Conditions table. You should then be able to add values for any combination of these three strata. If you want initial conditions to be determined by just the Primary Stratum (i.e., PVT), then do not add the optional Secondary and Tertiary columns. See example below:

If you want to customize the names of these strata to be more specific to your model, you can do so in the Project Definitions – Terminology tab. See example below:

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