On the Ecology of Mountainous Forests in a Changing Climate: A ...

The forest model FORCLIM 89
All the simulation studies with the FORCLIM model were run on Apple Macintosh computers,
using the computer models SE/30 (CPU Motorola 68030, FPU Motorola 68882),
IIfx (68030/68882) and Quadra 700 (68040, with integrated FPU). For efficiency
reasons, the object code of all the models was generated using the Compile20 option of
the MacMETH environment (Wirth et al. 1992), which produces code that addresses the
mathematical coprocessor directly, thus bypassing the much slower Standard Apple
Numerical Environment (SANE).
3.5.2 Coupling the submodels
The three submodels FORCLIM-E, FORCLIM-P, and FORCLIM-S each were implemented
as ModelWorks models of their own (Fischlin et al. 1990). One important aim of the
model implementation was that the behaviour of each of the three submodels can be
studied irrespective of whether one or both of the other submodels are present. Thus, if
one of the submodels is not present, there must be a mechanism that provides a constant
parametrization of its output variables. To this end the module ForestBase was introduced,
which contains always a pseudo-model. At the startup of FORCLIM, this pseudomodel
declares all the input/output variables of all the potential FORCLIM submodels as
model parameters. Every submodel that is declared in ModelWorks subsequently removes
the parameters corresponding to its output variables and supplies their values
based on its dynamics. In case the user removes a submodel, ForestBase declares the respective
parameters in the pseudo-model again. Thus all the variables coupling the
FORCLIM submodels have always well-defined values (Fig. 3.13).
The module structure of the FORCLIM system is shown in Fig. 3.14, and the matrix of
module dependencies is given in Tab. 3.18. FORCLIM-E and FORCLIM-S are implemented
as one single module each. The six modules making up FORCLIM-P serve the
following purposes:
FCPBase provides a dynamic list of Modula-2 records with variables describing the tree
species, i.e. the species-specific growth factors and parameters. A list of tree cohorts is
attached to each tree species. Again, each tree cohort is described by a Modula-2 record
containing the cohort-specific state and auxiliary variables. FCPBase also offers procedures
for adding species and cohorts to and deleting them from these lists. Moreover, a
procedure for the interactive editing of the species parameters is exported.