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

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18 Chapter 2 Swiss Plateau, which are much richer both in terms of species composition, total biomass, and soil fertility (cf. Appendix III for the location and climatic data of the sites). The additional site-specific parameters required by FORECE for the two sites are given in Tab. 2.2. The simulations covered 12'000 years at each site. Emanuel et al. (1978) used spectral analysis to evaluate the behaviour of the FORET model (Shugart & West 1977). They found that up to 0.05 cycles per year account for a considerable portion of the spectral energy, corresponding to cycles with a length of 20 years. To resolve these cycles, the sampling interval must not be larger than half the cycle length. Thus the monitoring interval was set to 5 years in order to allow for an estimation of the spectrum of the model output. Statistical analyses of the time series data (Shumway 1988) were performed by means of the SYSTAT V5.2.1 software (Wilkinson et al. 1992) on Apple Macintosh computers. The first 1'000 years of each simulation were discarded in order to concentrate on model behaviour after the transient phase. Tab. 2.2: Additional site-specific parameters required by the FORECE model for the sites Bern and Davos (from Kienast 1987 and Kienast, pers. comm.; cf. Kienast & Kuhn 1989a,b). Parameter Davos Bern Maximum aboveground biomass [t/ha] 300 540 Field capacity [cm] 27 30 Wilting point [cm] 20 20 Start of vegetation period [day number] 150 120 End of vegetation period [day number] 227 273 Frost threshold (March) [°C] 1.0 3.5 Frost threshold (April) [°C] 4.0 6.5 Frost threshold (May) [°C] 8.0 9.5 Soil moisture indicator value [–] 4 5 Seed for random number generator -12'672 -12'672 RESULTS & DISCUSSION Davos A typical part of the time series of species biomasses and tree numbers at the site Davos is shown in Fig. 2.2. From the point of view of biomass (Fig. 2.2 top), Norway spruce (Picea excelsa) is the dominating species. Swiss stone pine (Pinus cembra) becomes im-
Analysis of existing forest gap models 19 portant only after gap formation (years 7'500-7'600, 8'300-8'550), and the occurrence of alder (Alnus viridis) is episodic when large gaps have been formed by the death of canopy dominants (year 8'550). Tree numbers (Fig. 2.2 bottom) exhibit strong fluctuations, with peaks occurring generally after biomass has been low. However, there is no obvious relationship between the height of the peaks of tree numbers and the values of the biomass minima. The reason is that gap formation principally allows for increased sapling establishment because of higher light availability, but actual establishment rates are modified by other factors such as weather as well. 300 Davos Biomass (t/ha) 200 100 Alnus viridis Pinus cembra Picea excelsa 0 7500 8000 8500 9000 Simulation year 9500 10000 3000 number (#/ha) 2000 1000 Picea excelsa Pinus cembra Alnus viridis Tree 0 7500 8000 8500 9000 Simulation year 9500 10000 Fig. 2.2: Excerpt from the simulation results of a single forest patch at the site Davos. Top: Cumulative species-specific biomass. Bottom: Tree numbers.
Page 1: Diss. ETH No. 10638 On the Ecology
Page 4 and 5: ii Table of contents A BSTRACT.....
Page 6 and 7: iv APPENDIX .......................
Page 8 and 9: vi Harald BUGMANN, 1994: On the eco
Page 10 and 11: viii Harald BUGMANN, 1994: Aspekte
Page 13 and 14: 1 1 . Introduction 1.1 Climatic cha
Page 15 and 16: Introduction 3 1.2 Methods for the
Page 17 and 18: Introduction 5 in a changing climat
Page 19 and 20: Introduction 7 Their integrative ca
Page 21 and 22: Introduction 9 (1984) provides a mo
Page 23 and 24: Introduction 11 The main advantage
Page 25 and 26: 13 2 . Analysis of existing forest
Page 27 and 28: Analysis of existing forest gap mod
Page 29: Analysis of existing forest gap mod
Page 39 and 40: The forest model FORCLIM 45 carbon
Page 41 and 42: The forest model FORCLIM 47 TREE GR
Page 43 and 44: The forest model FORCLIM 49 gBFlag
Page 45 and 46: The forest model FORCLIM 51 Disturb
Page 47 and 48: The forest model FORCLIM 53 decay o
Page 49 and 50: The forest model FORCLIM 55 the est
Page 51 and 52: The forest model FORCLIM 57 3.3 Mod
Page 53 and 54: The forest model FORCLIM 59 Light a
Page 55 and 56: The forest model FORCLIM 61 Overall
Page 57 and 58: The forest model FORCLIM 63 D (cm)
Page 59 and 60: The forest model FORCLIM 65 a) b) c
Page 61 and 62: The forest model FORCLIM 67 Growth
Page 63 and 64: The forest model FORCLIM 69 Stress-
Page 65 and 66: The forest model FORCLIM 71 Tab. 3.
Page 67 and 68: The forest model FORCLIM 73 3.3.2 F
Page 69 and 70: The forest model FORCLIM 75 where k
Page 71 and 72: The forest model FORCLIM 77 NITROGE
Page 73 and 74: The forest model FORCLIM 79 peratur
Page 75 and 76: The forest model FORCLIM 81 of degr
Page 77 and 78: The forest model FORCLIM 83 microcl
Page 79 and 80: The forest model FORCLIM 85 Tab. 3.
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The forest model FORCLIM 87 3.4.3 F
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The forest model FORCLIM 89 All the
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The forest model FORCLIM 91 The mas
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The forest model FORCLIM 93 FORCLIM
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Behaviour of FORCLIM along a transe
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Parameter sensitivity & model valid
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153 6 . Model applications Climatic
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Model applications 155 The simulate
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Model applications 157 6.2 Possible
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Model applications 159 simulation s
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Model applications 161 Simulation e
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Model applications 163 At the site
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Model applications 165 Bever Biomas
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Model applications 167 tainty inher
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Model applications 169 scenario cho
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Discussion 171 Finally, the analysi
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Discussion 173 bitrarily chosen par
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Discussion 175 comparably small imp
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Discussion 177 end of the 21st cent
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Conclusions 179 Ecological factors
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Conclusions 181 species composition
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References 183 Begon, M., Harper, J
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References 185 Burger, H., 1951. Ho
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References 187 Faber, P.J., 1991. A
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References 189 Huntley, B. & Birks,
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References 191 Leemans, R. & Prenti
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References 193 Olson, J.S., 1963. E
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References 195 Rudloff, W., 1981. W
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References 197 Smith, T.M., Leemans
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References 199 Whittaker, R.H., 195
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Appendix 201 II. Derivation of para
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Appendix 203 Tab. A-4: Tree species
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Appendix 205 Tab. A-7: Values for m
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Appendix 207 The minimum winter tem
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Appendix 209 Tab. A-11: Shade toler
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Appendix 211 Tab. A-14: Climatic pa
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Appendix 213 IV. Source code of the
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Appendix 215 FROM SimBase IMPORT De
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Appendix 217 END; (* IF *) prevDay
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Appendix 219 PROCEDURE InitializeFW
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Appendix 221 InstallSeparator( fMen
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Appendix 223 FROM FCPFileIO IMPORT
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Appendix 225 modelSp^.p.kHm := sens
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Appendix 227 DeclMV( meanLitt[leafS
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Appendix 229 Swiss Federal Institut
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Appendix 231 (*********************
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Appendix 233 BEGIN WITH sp^ DO d :=
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Appendix 235 Definition module FCPB
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Appendix 237 Purpose Simulation mod
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Appendix 239 END Immobilization; PR
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Appendix 241 CONST lem = 3; VAR ef:
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Appendix 243 Purpose Provides the b
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Appendix 245 Example of a text file
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Appendix 247 Tab. A-15: Lower end o
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Appendix 249 Tab. A-17: Percentage
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Appendix 251 Tab. A-19: Significant
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Appendix 253 VI. Derivation of para
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Appendix 255 Tab. A-21: Species-spe
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Appendix 257 Tab. A-22 (continued)
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