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

Parameter sensitivity & model validation 129
Tab. 5.4: Advantages and deficiencies of various data sources for a model validation study. The following
ranking is used for the criteria: Spatial and temporal coverage: + high, – low; Climatological gradient: +
data contain a climatological gradient in time or space; – no climatological gradient can be derived from
the data; Management: + low, – high; Mapping: + data can be mapped easily to an output of the model,
– data can not be mapped directly to model output; Correspondence: + data corresponds to the output of a
mixed-age, mixed-species forest gap model of unmanaged stands, – data is from another type of forest or
another scale; Effort required: + effort for providing data and simulating these conditions is low, – major
effort is required.
Criterion
Yield
tables
Iventories
Forest
reserves
Tree
rings
Pollen
data
Remote
sensing
Phytosociol.
descriptions
Spatial coverage ? + – – – ++ +
Temporal coverage + – (+) ++ ++ – –
Climatological gradient – + (+) ++ ++ + +
Management – – + ? + – +
Mapping ++ + + + – – +
Correspondence – + + – – – +
Effort required – – – + – – +
conditions that the model has not been developed for, would constitute a truly independent
source of data; the forests simulated by FORCLIM could be compared to those
simulated by other forest gap models and to descriptions of the near-natural forests of the
area. Therefore, in a second validation experiment the performance of FORCLIM shall be
examined along a latitudinal gradient in eastern North America (section 5.4).
5.3 Behaviour of FORCLIM in central Europe
5.3.1 Derivation of input data
The scheme developed by Rehder (1965) and Ellenberg (1986) on the dominating species
in near-natural forests of central Europe is redrawn in Fig. 5.1. The climatological space
spanned by annual mean temperature and annual precipitation sum in Fig. 5.1 ranges
from the alpine timberline (bottom) to insubrian and mediterranean forests (top) and from
the dry timberline (left) to humid forests (right).
This climatological space with the associated forests presents a challenge to the FORCLIM
model: FORCLIM can not be applied directly to simulate these forests because it requires
climatic input data of monthly resolution (cf. Appendix III). However, if the annual cycle