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This model is based on Daniel Botkin's JABOWA model, and was developed by my Math 14 Mathematical Modeling class, Fall 2008, to simulate trees in the forest surrounding the Quabbin reservoir. I have added to the model since then.
--Tanya Leise, 4/9/2009
For more information about the principles behind the JABOWA model, see Botkin's book:
Botkin, D.B., 1993. Forest Dynamics: An Ecological Model, Oxford University Press, N.Y..
First press the setup button to create an initial population of trees (based on data for trees in Plot 206 of the Quabbin forest, using the MA DCR Continuous Forest Inventory from 1980). Then press go; each tick represents a year. Each square patch represents a 10 meter by 10 meter plot of land. The clear cut button clears all of the trees from a middle section of the forest. The vertical slider can be used to lower or raise the annual temperature range.
As they grow bigger, a small number of trees will dominate their patches. When a large tree dies, a bit of land is cleared, opening the way for saplings to pop up. Sun-loving species tend to take over such clearings initially, and then a natural succession of species occurs, leading eventually to a few large trees again and creating a natural cycle.
For cooler temperatures, the white pine thrive and many white pines grow to be quite large, while the red maples remain small. For hotter temperatures, let the model run for a while and observe the changes to the histograms for white pine and red maple. Also notice in changes the general size of trees and the change in species composition of the forest.