SORTIE-NDSoftware for spatially-explicit simulation of forest dynamics
Disperse behaviors create and distribute tree seeds around the plot. Dispersal is the first step in seedling recruitment.
Seed totals for different species are stored in the Dispersed Seeds grid. Each of the disperse behaviors adds seeds to this grid. The Establishment behaviors decide which seeds in the grid turn into new seedlings.
For these behaviors, "parent trees" refers to trees over the minimum reproductive DBH for a species. These are the only trees which can contribute new seeds to the plot.
While there is support in the model for seeds to act as individuals (see Tree life history stages), these seeds are not individuals but merely numbers in a grid. You could not, for instance, create a list of individual seed positions.
The numbers of seeds added by the disperse behaviors can be randomized. You choose how randomization will be applied. If the seed distribution is deterministic, no randomization is done. Otherwise, you can choose a probability distribution function and the number of seeds is treated as the mean of that function. You may need to supply additional parameters, depending on the probability distribution function you choose. This randomization applies to the seeds from all disperse behaviors that you have chosen.
There are four choices for probability distribution functions: the normal, the lognormal, the Poisson, and the negative binomial. The forms for these functions can be found here.