Plastic tree crowns contribute to small-scale heterogeneity in virgin beech forests-An individual-based modeling approach
Authored by Uta Berger, Markus Engel, Michael Koerner
Date Published: 2018
DOI: 10.1016/j.ecolmodel.2018.03.001
Sponsors:
No sponsors listed
Platforms:
R
Model Documentation:
ODD
Flow charts
Mathematical description
Model Code URLs:
Model code not found
Abstract
Old-growth beech (Fagus sylvatica L.) forests in Europe show a
structural heterogeneity, which distinguish from managed ones. Recent
investigations revealed that facilitative belowground interactions might
counteract aboveground competition for light. However, the exact
interaction of these mechanisms is unclear. We developed the
BEEchPlasticity (BEEP) model to investigate whether the mere focus on
the aboveground competition for canopy space with subsequent modeling of
the light transmittance through the forest canopy suffices to reproduce
the observed structural attributes. The BEEP model is individual-based,
and explicitly describes the plasticity of tree crowns in a
three-dimensional space through a geometric approach. This conceptual
design allows tracing neighborhood effects to the forest stand level.
We ran 10 simulation experiments with 1000 time steps on a simulation
area of 0.5oha. We analyzed the emerging spatial point patterns, gap
dynamics as well as distributions of tree age, tree height, tree crown
projection area, and tree diameter. By applying various indices that
revealed the emergent horizontal and vertical forest structure, we were
able to show a strong mutual link between beech crown plasticity and
forest heterogeneity. The crown plasticity enabled the trees to close
small gaps, which resulted in a highly dynamic tree regeneration, which
in turn led to a small-scale heterogeneous forest structure. We found
that, over long periods, crown centroids of canopy trees taller than
20om were more regularly distributed than stem foot points. Absolute
crown displacements were greater than reported from beech stands in
North-Germany and the Sudetes in the Czech Republic. This indicates a
need to restrain the model crown growth in order to recognize tree
architecture and stability. We could simulate an increasing forest
structural heterogeneity. Starting with a structural homogeneous layer
of tree saplings, we showed that forest structures similar to those in
unmanaged beech forests took several tree generations or approximately
700 time steps to emerge. We recommend enhancing this model approach
with spatial explicit modeling of the leaf-area distribution, which has
already been done for single beech trees.
Tags
Competition
Dynamics
pattern
Fagus-sylvatica l.
Beech
Fraxinus-excelsior
Old-growth forests
Soil-moisture
Fagus sylvatica l.
Crown plasticity
Pinus-sylvestris l.
European beech
Light availability
Gap size