On the Ecology of Mountainous Forests in a Changing Climate: A ...
On the Ecology of Mountainous Forests in a Changing Climate: A ...
On the Ecology of Mountainous Forests in a Changing Climate: A ...
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128 Chapter 5<br />
<strong>in</strong>dependent <strong>of</strong> those observations used to structure <strong>the</strong> model and to estimate its<br />
parameters (Shugart 1984).<br />
The FORCLIM model was developed to allow for projections <strong>of</strong> forest dynamics <strong>in</strong> a<br />
chang<strong>in</strong>g climate; thus its validation should deal with its behaviour along climatological<br />
gradients. There is a wealth <strong>of</strong> observations on past and current forests <strong>in</strong> central Europe<br />
that potentially could be used to validate various aspects <strong>of</strong> forest gap models, such as<br />
• Yield tables (e.g. Anonymous 1983, Schober 1987)<br />
• Forest <strong>in</strong>ventories (Z<strong>in</strong>gg & Bach<strong>of</strong>en 1988, Mahrer 1988)<br />
• Forest reserves (Leibundgut 1978, Broggi & Willi 1993)<br />
• Tree-r<strong>in</strong>g chronologies (Schwe<strong>in</strong>gruber et al. 1984, Briffa et al. 1990)<br />
• Pollen records (Huntley & Birks 1983, Ammann & Tobolski 1983, Lotter<br />
1988, Birks 1990, Huntley 1992)<br />
• Remotely sensed data (Guyenne & Calabresi 1989, Blasco & Achard 1990,<br />
Runkel 1990, Roughgarden et al. 1991, Hall et al. 1991, Treviño Garza 1992)<br />
• Phytosociological descriptions <strong>of</strong> <strong>the</strong> potential near-natural forest types<br />
(Schmid 1949, Ellenberg & Klötzli 1972, Ellenberg 1986)<br />
The advantages and deficiencies <strong>of</strong> <strong>the</strong>se data sources are summarized <strong>in</strong> Tab. 5.4. It<br />
becomes evident that <strong>the</strong>re is no “ideal” source <strong>of</strong> data for <strong>the</strong> validation <strong>of</strong> FORCLIM.<br />
Most <strong>of</strong> <strong>the</strong> criteria <strong>in</strong> Tab. 5.4 are met by data from forest reserves and by phytosociological<br />
descriptions. While <strong>the</strong> former are available at a few sites only and thus hardly<br />
allow to study climatological gradients, <strong>the</strong> latter do not cover <strong>the</strong> temporal aspects <strong>of</strong><br />
forest dynamics. However, Rehder (1965) and Ellenberg (1986) developed an <strong>in</strong>terest<strong>in</strong>g<br />
approach that was based on a large body <strong>of</strong> phytosociological data: They developed a<br />
scheme that presents <strong>the</strong> dom<strong>in</strong>at<strong>in</strong>g species <strong>of</strong> near-natural forests <strong>of</strong> central Europe <strong>in</strong> a<br />
climatological space spanned by <strong>the</strong> annual mean temperature and <strong>the</strong> annual precipitation<br />
sum (Fig. 5.1). A simulation study <strong>of</strong> <strong>the</strong>se forests could provide detailed <strong>in</strong>formation<br />
about <strong>the</strong> changes <strong>of</strong> <strong>the</strong> species composition along climatic gradients under current climate<br />
and <strong>the</strong> agreement <strong>of</strong> <strong>the</strong> simulated forests with those hypo<strong>the</strong>sized by <strong>the</strong> two<br />
authors. These advantages outweigh <strong>the</strong> static nature <strong>of</strong> <strong>the</strong>se descriptions; hence section<br />
5.3 shall deal with such an analysis.<br />
FORCLIM was constructed us<strong>in</strong>g an altitud<strong>in</strong>al gradient <strong>in</strong> <strong>the</strong> European Alps (chapter 4).<br />
Thus, ano<strong>the</strong>r transect <strong>in</strong> <strong>the</strong> same area would not be really <strong>in</strong>dependent <strong>of</strong> <strong>the</strong> first one.<br />
However, a similar transect <strong>in</strong> ano<strong>the</strong>r cont<strong>in</strong>ent, i.e. with a set <strong>of</strong> species and climatic