SORTIE-NDSoftware for spatially-explicit simulation of forest dynamics
Storm Light behavior
This behavior calculates light levels as a function of number of trees damaged in storms. Light levels are stored in a grid for later retrieval by other behaviors; this behavior does not directly assign light to trees.
Parameters for this behavior
How it works
The light level is calculated as follows:
This behavior calculates the light levels at the center of each grid cell by examining the trees within the distance given in the Storm Light - Max Radius (m) for Damaged Neighbors parameter.
The first term in the equation, ((1 - T/M) * 100), corrects the light level if the point is not under full canopy. All adults and snags, no matter what storm damage, are counted up and assigned to T. If T > = M, then the first term is set to 0 and only the second part, (a + b * N), is evaluated. If T < M, then the first term adds to the linear portion the proportion of full sun equal to the proportion of trees missing from the full canopy.
For the second, linear term, the behavior counts the number of dead and heavily damaged trees as a proportion of all adults and snags. Trees count as heavily damaged if they are either snags that were created as a result of a storm killing an adult tree, or live adults with heavy storm damage. All storm damaged trees have a time-since-damage counter; only those eligible trees with a counter value less than or equal to the value in the Storm Light - Max Years Damaged Trees Affect Light parameter are counted. Saplings and seedlings never count. All snags count, whether they were created by a tree or another mortality process. Their age as a snag must also be less than the Storm Light - Max Years Snags Affect Light parameter.
The GLA value can be used as-is, or it can be used as the mean in a PDF to introduce a stochastic element. You can choose either "Normal" or "Lognormal" in the Storm Light - Stochasticity parameter, then supply a standard deviation in the Storm Light - Standard Deviation parameter. Using "Deterministic" as the stochasticity causes the GLA to be used as-is.
How to apply it
You do not need to apply this behavior to individual trees. While it is recommended that you also include the Storm damage applier behavior in your run, this is not required.