Environmental Engineering Reference
In-Depth Information
remaining segments without needle biomass and outside the cone of potential shadow-
ing. In the body of the loop, the weighted needle mass of each shadowing segment is
then calculated according to (11.1) and summed up to the total shadowing biomass of
segment s.
for ((* b:Tree (- -
>
)* a:Segment,
(s.getParent( ) !
b && b.getLastChild() in cone(s, alpha)
&& a[needleMassTotal]
¼
>
0.0 && a in cone(s, alpha)) *))
{
s[externalShadowingBiomass] +
¼
(a[needleMassTotal]
* b[lightTransmissionCoefficient] / (distanceSquared(a, s)
+ b.calculateNeedleMassDistributionCorrectingTerm( )));
};
This approach for modelling competition for light has a high degree of generic-
ness, i.e. it can easily be adapted to other biomass distributions or to more detailed
tree models which take asymmetric crown shapes or even an exact branching
system architecture into account.
The presented conifer model was developed as part of a larger, distributed
simulation system which also provides a 3D graphical interface with possibilities
of interactive manipulation of single trees (see Lanwert 2007). It is intended to be
used in e-learning scenarios where a group of students can test forest management
practices by cutting virtual trees and evaluating the consequences on future growth
of the remaining stand. Since the growth model is based on local light conditions
and thus on the 3D canopy structure in the vicinity of each tree, it allows to assess
different strategies of logging.
11.8 Outlook
Rule-based functional-structural modelling is suitable in situations when the three-
dimensional structure of an organism or of a community has an important influence
on its development. This is not only the case for tree crowns competing for light, but
also, e.g. for some plant-animal interactions. There have been first attempts to
model the movement and foraging behaviour of animals with extended L-systems
(Kurth and Sloboda 2001). Probably, a significant number of agent-based and
individual-based models, as covered by Chap. 12, can also be embedded in a
grammar-based framework in the future.
Another active field of research in functional-structural plant models addresses
the genetic basis of plant metabolism and regulatory networks. For example, a
“barley breeder” model, implemented in the language XL, enables virtual breeding
in a genetically heterogeneous population and simulates the hormonal control of
internode elongation in barley via a metabolic network (Buck-Sorlin et al. 2007).
On the technical side, a recent effort (Hemmerling et al. 2010) aims at providing
