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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126 Chapter 5<br />
The large sensitivity to kDrT (Tab. 5.3) found <strong>in</strong> <strong>the</strong> present study is primarily a consequence<br />
<strong>of</strong> <strong>the</strong> large plausibility range <strong>of</strong> this parameter; it po<strong>in</strong>ts to <strong>the</strong> need for fur<strong>the</strong>r research<br />
on <strong>the</strong> drought tolerance <strong>of</strong> <strong>the</strong> tree species and <strong>the</strong>ir response to drought stress.<br />
RESPONSE OF PARTICULAR SPECIES TO PARAMETER CHANGES<br />
The data from this analysis (cf. Appendix V) also suggest that <strong>the</strong> parameters kNTol, kG,<br />
kL y , and kL a are most important for shap<strong>in</strong>g species performance. O<strong>the</strong>r parameters such<br />
as kDm, kAm, kDDM<strong>in</strong>, and kDDMax were found to be important for some species that<br />
have low abundance. However, even if <strong>the</strong> relative change <strong>of</strong> <strong>the</strong>ir biomass was positive<br />
and high, <strong>the</strong>y did not atta<strong>in</strong> considerable biomass; for example, <strong>the</strong> biomass <strong>of</strong> Tilia<br />
platyphyllos <strong>in</strong>creased by 8510.6% (!) when its kDDM<strong>in</strong> parameter was lowered, yet it<br />
reached a biomass <strong>of</strong> 1.6 t/ha only. Thus, it may be concluded that <strong>the</strong> biomass estimates<br />
<strong>of</strong> m<strong>in</strong>or species are not robust to parameter changes, and <strong>the</strong> simulated abundance <strong>of</strong><br />
those species should not be <strong>in</strong>terpreted quantitatively.<br />
5.1.4 Conclusion<br />
The analysis <strong>of</strong> <strong>the</strong> sensitivity <strong>of</strong> FORCLIM to <strong>the</strong> values <strong>of</strong> its species parameters revealed<br />
<strong>the</strong> follow<strong>in</strong>g:<br />
The species composition simulated by FORCLIM appears to be quite robust to changes <strong>of</strong><br />
species parameters. Specifically, <strong>the</strong>re are no suppressed species that atta<strong>in</strong> large biomass<br />
when one <strong>of</strong> <strong>the</strong>ir species parameters is changed. <strong>On</strong> <strong>the</strong> o<strong>the</strong>r hand, <strong>in</strong> some <strong>in</strong>stances<br />
<strong>the</strong> biomass <strong>of</strong> <strong>the</strong> most abundant species may decrease considerably, but <strong>the</strong>y still rema<strong>in</strong><br />
characteristic <strong>of</strong> <strong>the</strong> simulated forest.<br />
The abundance <strong>of</strong> <strong>the</strong> species may vary markedly depend<strong>in</strong>g on <strong>the</strong> parameter values<br />
used. Thus <strong>the</strong> simulated quantity <strong>of</strong> a given species should be <strong>in</strong>terpreted cautiously.<br />
This may be <strong>in</strong>terpreted <strong>in</strong> <strong>the</strong> context <strong>of</strong> <strong>the</strong> scheme proposed by Lev<strong>in</strong>s (1966): Forest<br />
gap models may be general and realistic, but <strong>the</strong> precision <strong>of</strong> <strong>the</strong> simulated species composition<br />
is ra<strong>the</strong>r low.<br />
The FORCLIM model appears to be most sensitive to <strong>the</strong> values <strong>of</strong> <strong>the</strong> kNTol parameter,<br />
po<strong>in</strong>t<strong>in</strong>g to <strong>the</strong> need for fur<strong>the</strong>r research on soil organic matter dynamics and nutrient