The Build Stress Maps Scenario


Introduction

The Build Stress Maps scenario constructs a stochastic spatial data time series from a single static patch map. The Build Patch Map scenario describes how the patch map used here was constructed. When the Build Stress Maps model is run, each cycle through the event sequence produces a new Generated Hexmap (see example to the right). This scenario was developed to create a spatial data time series for the HexSimPLE scenario. However, these spatial data aren't derived from a real map, whereas in a targeted HexSimPLE application the habitat and stress maps would likely describe actual landscapes and disturbance frequencies. In such cases, the techniques illustrated here may or may not be needed.

Population Parameters

Population parameters are almost entirely unused in this model. The Properties tab sets the initial population to zero, and the Range Data tab has only null values. The model does not have any Affinities, and uses a single accumulator. A probabilistic trait has been added because, to be valid, HexSim simulations must contain at least one trait. But this trait is not used.

Event Sequence

The model has just three life history events. First, a Patch Introduction event adds a single individual to each patch in the Patch Map. This event also sets each individual's explored area equal to its entire patch. The second event assigns a random number to each individual's Value accumulator. The random values are drawn from N(25, 25), but are clipped to [0, 100]. The final life history event constructs a Hexmap from the individual Value accumulators. The Generated Hexmap event is set up to write each individual's Value accumulator to every hexagon in its explored area. This creates a copy of the patch map in which each patch is assigned a random number.

Users wanting to make simple changes to this scenario will probably focus initially on the patch map structure or the distribution used to assign random values to individual patches. Changes to the patch map structure can be made within the Build Patch Map scenario, or a new patch map could be constructed using other HexSim tools, or outside of HexSim entirely. To alter the distribution used to assign random values to the patches, users need only edit the Set Patch Value Accumulate event.

Using the Scenario

This scenario requires a Hexmap named Patch Map, which is constructed by the Build Patch Map scenario. After the Build Stress Maps scenario has been run, the Results folder will contain a output spatial data time series named Stress Map Series. Anytime this scenario is run, the following steps will be necessary to make its output spatial data available to the HexSimPLE model.

  • Close any open scenario tabs.
  • Quit HexSim.
  • Navigate to the Build Stress Maps results folder.
  • Move the Stress Map Series sub-folder to the workspace spatial data (under Hexagons).
  • Delete the old spatial data time series being replaced.
  • Start HexSim.
  • Rename Stress Map Series to Stress Map Survival or Stress Map Fecundity.