Environmental Engineering Reference
In-Depth Information
Fig. 12.1 Basic scheme of
a class to represent an
individual (Breckling et al.
2006
)
coordinates related to an individual's location (Jopp and Reuter 2005). In most
cases, the number of variables describing individual properties is considerably
higher. Besides location, they often comprise biomass, age, sex and a relational
context. For instance, when the object refers to plant modules, information on
neighbouring modules is decisive to determine transport processes. For many
higher animals e.g. the information on a home range (or territory) or on eventual
offspring that have to be fed, may be necessary.
b) Code to Update Individual Properties
It is useful to organize the updating of an individual's state in terms of a set of
“activity procedures” (changing states relevant with regard to the environment) and
“physiological processes” (changing states referring to the internal condition of the
individual). Common examples for activity procedures are movement, reproduc-
tion, and feeding. Physiological processes represented in a model can be ageing and
energy metabolism. The according procedures access and update the involved
variables. For example, an activity “movement” should change the variables storing
the location information. If energetic processes are included, “movement” may also
change the energetic state to include the cost of the particular activity. The
description of activities can be accomplished with very simple rules and can also
integrate other mathematical approaches like fuzzy logic (see Chap. 10) or differ-
ential equations (see Chap. 6). The decision which details should be included in an
activity procedure depends on the focus of the model, the available knowledge and
information status of the ecologist. As the ecological quality of the input informa-
tion basically decides the character of the model as a whole, we advocate that
ecologists, with the necessary knowledge at hand, should be intensively involved in
the programming process or better yet, learn to program their own models instead of
relying on specialized programmers or pre-defined software tools which usually
restrict the optimal adaptation to what the specific situation requires.
