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

160 Chapter 6
practice. Third, the regionalized scenarios of climatic change (Gyalistras et al. 1994) for
the sites Bever, Davos, and Bern were taken from Bugmann & Fischlin (1994).
Uncertainty inherent in climate scenarios
Some of the uncertainty inherent in the regionalized scenarios of climatic change can be
quantified explicitly (Gyalistras et al. 1994), whereas this would be more difficult for the
IPCC scenario (Fischlin et al. 1994); for the Kienast scenario, it is hardly feasible. Thus,
the regionalized scenarios of climatic change at the sites Bever, Davos, and Bern were
selected to study the uncertainty inherent in a given climate scenario (Tab. 6.3).
Tab. 6.3: Uncertainty inherent in the regionalized scenarios of climatic change (Tab. 6.2), expressed as
twice the standard deviation (2·σ) of the downscaling models (Gyalistras et al. 1994); these uncertainties
were also used in the gap model study by Bugmann & Fischlin (1994).
Site T Summer P Summer T Winter P Winter
Bern ±1.21 °C ±3.96 cm/mo ±1.33 °C ±1.72 cm/mo
Davos ±0.74 °C ±1.95 cm/mo ±1.26 °C ±3.18 cm/mo
Bever ±1.59 °C ±2.39 cm/mo ±0.94 °C ±1.20 cm/mo
Transient climatic changes
It is a common practice in systems theory to explore the response of a system to a step
change in the input data (Fig. 6.4). On the other hand, most of the previous impact assessments
using forest gap models
have adopted a linear change
of climatic parameters over time
(e.g. Solomon 1986, Pastor &
X c
step
Post 1988, Kienast 1991). In
linear (ramp)
reality, climatic change will
follow neither of these assumptions,
and a more gradual,
X 0
sigmoid
e.g. sigmoid change would be
more likely to occur. Thus, these
t 0 t 0 + 100
Fig. 6.4: Three types of transient climatic change that are
three types of climatic changes
explored in this study. X 0 : Long-term mean value of a
were used in the present study climatic variable (e.g., average of July temperature) under
current climatic conditions; X c : Long-term mean value of the
(Fig. 6.4).
variable under the climatic change scenario. The time axis is
in years; t 0 is the time when the climate starts to change.