This project corresponds to
the PhD thesis of Zhengyang Zhang
In Genève, Switzerland, July 2016.
SORTIE is a
forest simulator developed by Pacala, Ribbens, Kobe et al.
in 1993-1996. It is based on the forest data observed in
and around Great Mountain Forest (GMF), a privately owned
2500ha forest located in northwestern Connecticut (41°57'N, 73°15'W), USA in the year
1990-1992. SORTIE is an individual based model (IBM). It
consists of four submodels (resource, growth, mortality,
and recruitment) to determine the behavior of each
individual, from which the behavior of the whole forest
community can be determined. The main ingredient taken
into account in SORTIE is the competition for light
In  we build a mathematical model (a
state-dependent delay differential equation derived from a
size-structured model) for the adult population of trees
A(t) in two cases (single species case and two-species
case) and we compare it with SORTIE. The models are
Left: single species case; right:
two-species case. See  for a detailed explanation.
This code provides
the following figure which is taken from .
this figure we plot the numerical simulation of the spatial
model, describing the spread of the adult population of the two species.
In  we use
the above model (in the single species case)
coupled as a predator-prey system. This is to
describe a parasite destroying a pine
forest. The parastite considered is the so
called "pinewood nematode" which destroyed a
large part of Portuguese pine tree forest. The
model we end up with is the following