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

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100 Chapter 4 main impact of climatic change would be on those pools of soil organic matter that have turnover rates in the order of centuries or less. These pools are modelled explicitly in FORCLIM-S, and the model thus appears to be appropriate for studying the effects of climatic change on belowground carbon storage during a few centuries. Tab. 4.3: Available nitrogen (uAvN, kg·ha -1 ), organic matter in the litter (LOM, t·ha -1 ) and humus compartments (HOM, t·ha -1 ), and their sum (SOM, t·ha -1 ). All values refer to the steady state as calculated by FORCLIM-S run in isolation. The input variables are taken from Tab. 4.1 & 4.4. Site uAvN LOM HOM SOM Bever N 72.6 57.7 256.8 314.5 Davos 77.6 62.4 98.2 160.6 Sion 94.1 110.9 48.0 158.9 Bever S 66.2 41.6 81.7 123.3 Bern 130.6 114.5 76.0 190.5 Locarno 138.3 124.3 75.7 200.0 While the simulated ratios of litter to humus mass are difficult to ascertain, it is possible to compare the simulated total amount of soil organic matter with measurements compiled by Richard et al. (1978; D. Perruchoud, pers. comm.): For the Swiss Plateau (elevation 700 m.a.s.l.) the average soil organic matter content calculated from the data in Richard et al. (1978) is 359 t/ha, ranging from 152 to 793 t/ha. If the podzols are excluded from the calculation, the average is 257 t/ha. Again, the amount of soil organic matter simulated by FORCLIM-S falls within that range (Bever, Davos). Another important index of soil organic matter is its residence time, which can be estimated as the ratio of total soil organic matter to the annual litter input in the steady state. The simulated residence times range from 11.15 years at Locarno to 32.86 years at northern slopes in Bever. These figures are considerably lower than those by Raich & Schlesinger (1992), which give 29 years for temperate and 91 years for boreal forests; the residence time simulated by FORCLIM-S is roughly three times less. Given that the estimates of litter production by FORCLIM-P were correct (cf. next section), this would mean that FORCLIM-S underestimates the amount of soil organic matter by a factor three, which appears unprobable when considering the data in Richard et al. (1978). Further research is required to address this issue.
Behaviour of FORCLIM along a transect in the European Alps 101 4.3 Model variants including FORCLIM-P According to the descriptions of near-natural forest communities in the central part of the European Alps (Ellenberg & Klötzli 1972, Ellenberg 1986), four sites typical of today's vegetation zones were selected to study the behaviour of FORCLIM-P (cf. Appendix III): First, a south-facing slope at Bever, where the near-natural vegetation is formed by larch- Swiss stone pine forests (Larici-Pinetum cembrae Ellenberg & Klötzli 1972). The dominating species in this association is Pinus cembra; subdominant species are Larix decidua and P. montana, while Picea excelsa occurs only rarely. Second, the site Davos with larch-spruce forests (Larici-Piceetum Ellenberg & Klötzli 1972). Picea excelsa is the most abundant species in this association, followed by L. decidua, P. cembra, and P. silvestris. Third, the site Bern where a variety of communities dominated by beech (Fagus silvatica) and oak species (Quercus robur, Q. petraea) forms the near-natural vegetation (Ellenberg & Klötzli 1972, Ellenberg 1986). Many other deciduous species occur in these forests, such as Acer spp., Fraxinus excelsior, and Ulmus scabra. Coniferous species like P. excelsa and Abies alba do not have a dominant role in these near-natural forests. Finally, forest succession is simulated at the site Sion, which is close to the dry timberline. Oak species (Quercus spp.) and Scots pine (Pinus silvestris) should prevail there (Ellenberg & Klötzli 1972). In a first step, the FORCLIM-P model was run in isolation, assuming constant weather and constant soil fertility. Next, the importance of FORCLIM-E was evaluated by coupling it to FORCLIM-P, yielding the model FORCLIM-E/P. Then the feedbacks between FORCLIM-S and FORCLIM-P were examined in the complete FORCLIM-E/P/S model. All simulations were run for 1200 years and 200 patches, starting with a bare patch as the initial condition both for FORCLIM-P and FORCLIM-S. 4.3.1 FORCLIM-P The constant values of the bioclimatic variables degree-days (uDD), winter temperature (uWiT), and drought stress (uDrStr) were taken from Tab. 4.1. A nutrient-rich soil with
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Diss. ETH No. 10638 On the Ecology
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ii Table of contents A BSTRACT.....
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iv APPENDIX .......................
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vi Harald BUGMANN, 1994: On the eco
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viii Harald BUGMANN, 1994: Aspekte
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1 1 . Introduction 1.1 Climatic cha
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Introduction 3 1.2 Methods for the
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Introduction 5 in a changing climat
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Introduction 7 Their integrative ca
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Introduction 9 (1984) provides a mo
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Introduction 11 The main advantage
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13 2 . Analysis of existing forest
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Analysis of existing forest gap mod
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The forest model FORCLIM 45 carbon
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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.
Page 81 and 82: The forest model FORCLIM 87 3.4.3 F
Page 83 and 84: The forest model FORCLIM 89 All the
Page 85 and 86: The forest model FORCLIM 91 The mas
Page 87 and 88: The forest model FORCLIM 93 FORCLIM
Page 89 and 90: Behaviour of FORCLIM along a transe
Page 93: Behaviour of FORCLIM along a transe
Page 115 and 116: Parameter sensitivity & model valid
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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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