Improving the formulation of tree growth and succession in a ...

192 S. Schumacher et al. / Ecological Modelling 180 (2004) 175–194
after such events. Studying transitions from weakly
to strongly disturbed landscapes is an important issue,
as global environmental change is likely to bring
about changes in the distribution of extreme climatic
events, which may trigger changes in the large-scale
disturbance regimes in many landscapes.
Because the modified model explicitly incorporates
the effects of a range of climatic factors on tree regeneration
and growth, it is more suitable for addressing
the direct impacts of climatic changes on forested
landscapes. Through a simple set of scenario calculations
(which should not be mistaken as predictions),
we were able to demonstrate that the model is sensitive
to changing climatic parameters. Notably, the effects
of climatic changes on forest landscape dynamics
are emergent properties of the modified model, rather
than being prescribed through site-specific or speciesspecific
parameters, which was the case in earlier versions
of LANDIS.
The modified model can also serve as a tool to
help with decision-making in the context of longterm
forest management. It provides variables—such
as biomass, stand density, species dominance, or vertical
structure—that can be used for assessing, for
example, the habitat requirements of wildlife, and indices
that are relevant to a range of other ecological
questions. Also, variables, such as stand density and
vertical stand structure are crucial for predicting the
long-term consequences of forest management decisions,
e.g. with respect to the ability of mountain forests
to avert natural hazards, such as avalanches, rockfall or
landslides.
Finally, the ability of the model to simulate
landscape-scale aboveground biomass storage allows
us to determine the effect of Global Change scenarios
on aspects of the carbon balance of mountain
ecosystems. Hence, the modified LANDIS model as
described in this study has the potential to provide an
integrated picture of the impact of both direct and indirect
effects of climate change on forest landscape
dynamics.
Acknowledgment
Thanks are due to Hong He, University of
Missouri—Columbia, who supplied the LANDIS
model and helped us to get acquainted with it. Dean
Urban and an anonymous reviewer provided constructive
criticisms of an earlier version of this manuscript.
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