PRESTO is the acronym for Plant Recruitment Eco-Simulation Tool. The model is defined as a process-based, spatially explicit, and stochastic computer model. Its two main purposes are to explore seed abundance versus substrate limitations according to various silvicultural activities (e.g. variable retention harvesting, site preparation…), and to serve as a template for LLEMS’s recruitment component.

PRESTO will produce spatially explicit quantitative estimates of natural regeneration based on easily measurable field variables such as seed mass, tree abundance, height, diameter, and seedbed types. These variables will be specified by the user (empirically), or generated by another model (i.e. FORECAST / FORCEE).

The spatial extent of PRESTO is determined by dispersal distances, which in turn are related to biotic and abiotic variables such as seed mass, terminal velocities, and wind profiles. The output resolution (raster cell size) will be relative to a user defined value (e.g. seedlings/1m2).

Processes will include seed production, seed dispersal, germination, and early establishment (mortality).

Stochasticity will enter at the seed production and establishment levels. This will be accomplished with the use of well-known probability distributions such as the log-normal distribution and random number generators.

Parameter estimates will be determined using maximum likelihood techniques. The model will run on an annual time step, tracking seedling cohorts throughout time. At the end of a simulation (e.g. ten years) a raster map will be produced showing the location of the seed trees along with the seedling abundance (sum of all cohorts).

Another potential purpose of PRESTO is to explore the efficiency of various silvicultural system designs (e.g. seed tree, shelterwood...) for achieving stocking success at the natural regeneration level.

For more information contact: rduchesneau@iqaff.qc.ca