This behavior simulates rodent seed predation, where rodent populations are a function of both tree masting level (as set by the Masting Disperse with Autocorrelation behavior) and population size in the previous timestep. This behavior will reduce the number of seeds dispersed. The leftover seeds that were not consumed by predators are available as input to the Establishment behaviors.
| Parameter name | Description |
|---|---|
| Dens Dep - Functional Response Exponent "a" | The exponent in the functional response component of the rodent population index. |
| Dens Dep - Density Dependence Coefficient | The coefficient in the density dependence component of the rodent population index. |
| Dens Dep - Functional Response Slope | The slope value for each species in the functional response component of the rodent population index. |
This behavior simulates a rodent population, and the number of seeds that they eat. Rather than simulating population numbers, this calculates the population index (λ) for a timestep in terms of proportion of maximum possible rodent population. The maximum possible population is that which is capable of eating all seeds. Therefore, the population index is equal to the amount of seed eaten. For example: if the rodent population index λ is 0.7 for a timestep, the population is 0.7 of the maximum possible population, and 0.7 of all seeds will be eaten.
The rodent population index at timestep t is calculated as follows:
Where funcresp is the population functional response, and densdep is the lagged density dependence term.
The functional response is calculated as follows:
where:
The lagged density dependence term is calculated as follows:
where:
In the first timestep, the densdep term is set to 1.
The seeds to which this behavior applies are treated as a common pool, consumed at the same rate. Once λt has been calculated, for each cell in the Dispersed Seeds grid, the number of seeds is reduced as final seeds = starting seeds * (1 - λt).
This behavior may be applied to seeds of any species. Any species to which it is applied must also have a Masting Disperse with Autocorrelation behavior applied as well.