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

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12 Chapter 1 To answer these questions, the following steps shall be followed: 1) The systems theoretical and ecological properties of FORECE shall be scrutinized, the significance of the ecological factors present in FORECE shall be evaluated, and the model shall be simplified in order to determine the smallest set of factors capable of simulating plausible patterns of forest succession in the European Alps (chapter 2). 2) Based on these analyses, a new forest gap model (FORCLIM) shall be developed, which encapsulates this set of ecological factors and does not include implicit assumptions about climate. Great care shall be taken to develop reliable formulations for the influence of climatic parameters on ecological processes (chapter 3). 3) The behaviour of the various submodels and of the complete model shall be evaluated along an ecological gradient in the European Alps (chapter 4). Then the sensitivity of FORCLIM to the species parameters shall be studied so that its limitations are better known, and its behaviour shall be tested extensively in function of climatic parameters (chapter 5). 4) The sensitivity of forest ecosystems to past climatic variations and anticipated future climatic changes shall be investigated at sites typical of today's vegetation zones in the European Alps (chapter 6). This thesis serves also as a case study in the project “Workstation-assisted Ecological Modelling & Simulation and the Impact of Climate Change on Ecosystems in an Alpine Region (FORAGROCLIM)” carried out by Systems Ecology at ETHZ, where tools for interactive modelling and simulation on personal computers and workstations are being developed (Fischlin 1991). These tools will be used and evaluated both for the analysis of FORECE and for the development of the FORCLIM model. Moreover, the thesis is a contribution to the established core project “Global Change and Terrestrial Ecosystems” (GCTE; Steffen et al. 1992) of the International Geosphere-Biosphere Programme (IGBP 1990). Specifically, it shall contribute to the modelling and understanding of the structure and functioning of terrestrial ecosystems, i.e. to Focus 2 (“Change in Ecosystem Structure”) and Activity 2.1 (“Patch Scale Dynamics”) of the GCTE project.
13 2 . Analysis of existing forest gap models This chapter starts with an analysis of the model formalism of forest gap models (section 2.1). Section 2.2 presents simulation studies with the FORECE model, which are used to exemplify the type of basic simulation results produced by forest gap models and to analyse some of their statistical properties. These considerations provide the basis for an ecological analysis in section 2.3: First, the sensitivity of the FORECE model to structural simplifications is investigated in order to derive a minimum set of ecological factors that are necessary to model forest dynamics in the European Alps (section 2.3.1). Second, the set of climate-dependent factors remaining after the simplification procedure is analysed for its sensitivity to alternate formulations (section 2.3.2). Throughout the thesis, the nomenclature of the European tree species follows Hess et al. (1980). Their scientific and common names are listed in Appendix I. 2.1 Model formalism Zeigler (1976) distinguished the following categories of model formalisms: Differential Equation System Specifications (DESS), Discrete EVent System Specifications (DEVS), and Sequential Machines (SM, i.e. discrete time models). It is often difficult to specify to which of these three formalisms complex models belong, because the mathematical equations are not published in detail, the various submodels may be based on different formalisms, or the formalism used for the mathematical model does not correspond to the one used in the simulation model, i.e. in the computer code. For example, the tree growth equation of forest gap models most often is described as a differential equation (DESS, Botkin et al. 1972a,b, Shugart 1984), while the descriptions of tree establishment and tree death suggest that these processes are simulated using a discrete event model (DEVS). However, forest gap models typically are implemented as discrete-time models (SM) with an annual time step. Hence, there arises the question to which formalism these models conform.
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: Introduction 11 The main advantage
Page 27 and 28: 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
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The forest model FORCLIM 81 of degr
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The forest model FORCLIM 83 microcl
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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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