SORTIE-ND
Software for spatially-explicit simulation of forest dynamics

# Non-spatial disperse

The "non-spatial" in non-spatial disperse refers to the fact that this behavior ignores the location of parent trees and scatters seeds uniformly across the plot. Non-spatial disperse has two components: basal-area-dependent seed rain and non-density-dependent (bath) seed rain, the two of which are independent and can be used together or separately. For basal-area-dependent seed rain, the number of seeds added is in direct proportion to the amount of basal area of parent trees of a given species. Bath seed rain adds a constant number of seeds each timestep, even if there are no parent trees of that species in the plot.

### Parameters for this behavior

Parameter nameDescription
Intercept of Mean Non-Spatial Seed Rain, seeds/m2/yrThe intercept of the non-spatial seed rain function. This is the bath seed rain term. Set this value to zero to turn off bath non-spatial seed rain.
Slope Mean Non-Spatial Seed Rain, seeds/m2/ha of BA/yrThe slope of the non-spatial seed rain function. This is the basal-area-dependent seed rain term. Set this value to zero to turn off basal-area-dependent non-spatial seed rain.
Minimum DBH for Reproduction, in cmThe minimum DBH at which a tree can reproduce. This value does not have to match the Minimum adult DBH.
Seed DistributionThe distribution method to be applied to seeds (randomization). The forms for these functions can be found here. Choices are:
• Deterministic - no randomization.
• Poisson - use the number of seeds as the mean in a Poisson probability distribution function.
• Normal - use the number of seeds as the mean in a normal probability distribution function. You must then supply a standard deviation for the function.
• Lognormal - use the number of seeds as the mean in a lognormal probability distribution function. You must then supply a standard deviation for the function.
• Negative binomial - use the number of seeds as the mean in a negative binomial probability distribution function. You must then supply a clumping parameter.
Seed Dist. Clumping Parameter (Neg. Binomial)If you have chosen the negative binomial probability distribution function for "Seed distribution", this is the clumping parameter of the function, in seeds per m2. If you have not chosen that PDFs, then this parameter is not required.
Seed Dist. Std. Deviation (Normal or Lognormal)If you have chosen the normal or lognormal probability distribution functions for "Seed distribution", this is the standard deviation of the function, in seeds per m2. If you have not chosen these PDFs, then this parameter is not required.

### How it works

Non-spatial disperse calculates how many seeds to distribute as:

λ = μ *BA + κ

where:
• λ is the mean number of seeds per m2
• μ is the Slope Mean Non-Spatial Seed Rain, seeds/m2/ha of BA/yr parameter
• BA is the basal area of the parent species in m2
• κ is the Intercept of Mean Non-Spatial Seed Rain, seeds/m2/yr parameter
From this, the number of seeds per grid cell of the Dispersed Seeds grid is calculated, and then that number is added to each grid cell.

In the equation above, μ is the basal-area-dependent seed rain term. Setting this value to zero turns off density-dependent seed rain. κ is the bath seed rain term. Setting this value to zero turns off bath seed rain.

### How to apply it

Apply this behavior to adults of the species you wish to use non-spatial disperse.