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

More documents

Recommendations

Info

154 Chapter 6 from the long-term distributions in Tab. 6.1. Then the years 1525 through 1979 were simulated using the reconstructed series of weather data from Pfister (1988) to calculate the bioclimatic variables in FORCLIM-E deterministically. The temperature and precipitation of months with missing values (Pfister 1988) were assumed not to deviate from the longterm statistics (Tab. 6.1). The latitude of the CLIMINDEX “site” is 47.5 °N (Swiss Plateau), field capacity was set to 30 cm, and nitrogen availability to 100 kg/ha. Tab. 6.1: Climatic data reconstructed from the thermic and hydric indices of the period 1901-1960 for the virtual site “CLIMINDEX” (Pfister 1988). Symbols: µ(T) – monthly mean temperature [°C]; σ(T) – standard deviation of T; µ(P) – monthly precipitation sum [cm/month]; σ(P) – standard deviation of P; r – cross-correlation coefficient of T and P. The long-term mean annual temperature of the CLIMINDEX site is 9.2 °C, and the annual precipitation sum is 1187 mm. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec µ(T) -0.2 1.3 5.2 8.8 13.5 16.5 18.3 17.5 14.4 9.2 4.3 1.3 σ(T) 2.6 2.1 1.9 1.7 1.7 1.3 1.5 1.3 1.5 1.5 1.5 2.3 µ(P) 10.23 9.83 9.75 9.82 9.85 9.60 9.66 9.93 9.47 10.55 9.97 10.05 σ(P) 4.93 6.09 4.66 3.41 3.06 4.01 3.33 2.82 2.89 5.46 5.97 3.58 r 0.33 0.27 -0.04 -0.22 -0.38 -0.46 -0.62 -0.49 -0.32 -0.17 0.22 0.4 6.1.2 Results & discussion The simulation results from the first phase of the experiment (Fig. 6.2) are similar to those obtained when running FORCLIM with the climate of the site Bern (cf. chapter 4). The simulated forest is characterized by a strong dominance of beech (Fagus silvatica) accompanied by silver fir (Abies alba) and oak (Quercus spp.). Due to the comparably high temperature, spruce (Picea excelsa) is outcompeted by those species. These results appear to be plausible (Ellenberg & Klötzli 1972). Degree-days (°C*d) 2200 2000 1800 1500 1600 1700 1800 Year 1900 2000 Fig. 6.1: Simulated annual sum of degree-days (1525-1979 AD) based on the monthly temperature indices from Pfister (1988). The graph shows moving averages over 15 years.
Model applications 155 The simulated winter temperature during the period from 1525 to 1979 was always above -5 °C; thus its ecological significance in the FORCLIM model is negligible (chapter 3). Similarly, the simulated drought stress is mostly below 10%, with a few exceptions where stronger drought occurred, the strongest being almost 30% in the “mediterranean” year 1540 (cf. Pfister 1988). Hence, the variable that could have the largest effect on simulated forest dynamics is the annual sum of degree-days (Fig. 6.1). Most of the periods outlined by Pfister (1988) as mid-term climatic variations are evident from Fig. 6.1, such as the warm period from 1530-1564, the maximum of the Little Ice Age from 1688- 1701, the rapid warming from 1702-1730, and the cool phase from 1812-1860. These variations had strong effects e.g. on agricultural yield (Pfister 1988) – did they also have effects on the characteristics of near-natural forests, such as species composition and total aboveground biomass? The simulated forest dynamics from 1525-1979 (Fig. 6.3) do not show any relationship to the climatic variations visible in Fig. 6.1. The variability of the simulated aboveground biomass is due to the stochastic formulation of tree establishment and mortality in FORCLIM (cf. Tab. 3.6), not to the changing abiotic environment. Thus, we may conclude that the forest simulated by FORCLIM-E/P at the CLIMINDEX site is well buffered against climatic variations of the duration and magnitude that occurred during the last 450 years, corroborating the findings by Davis & Botkin (1985). From an evolutionary point of view, these results are plausible as well: Trees typically have lifespans of several centuries; given the fact that climatic variations like the ones reconstructed by Pfister (1988) occur on the timescale of decades, trees must be capable of surviving such anomalies, otherwise they could not grow to adult size and would not be able to reproduce. Hence, the inertia to climatic variations of the simulated species composition probably is characteristic of real forests of the Swiss Plateau as well. However, these findings can not be generalized to other areas. For example, under conditions of strong environmental stress, such as close to the alpine or the dry timberlines, it is conceivable that climatic variations on the timescale of decades might lead to breakdown phenomena – at least in forest models. However, further studies would be required to address this issue. Finally, it should also be noted that this experiment could not have been performed using the FORECE model by Kienast (1987). In an earlier study, we have shown that the “dry days” approach incorporated in FORECE and other forest gap models leads to unrealistic forest breakdown events when the same realization of weather is used to drive successional dynamics on all the patches that are simulated (Fischlin et al. 1994).
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 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
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.
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 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98: Behaviour of FORCLIM along a transe
Page 115 and 116: Parameter sensitivity & model valid
Page 147: 153 6 . Model applications Climatic
Page 151 and 152: Model applications 157 6.2 Possible
Page 153 and 154: Model applications 159 simulation s
Page 155 and 156: Model applications 161 Simulation e
Page 157 and 158: Model applications 163 At the site
Page 159 and 160: Model applications 165 Bever Biomas
Page 161 and 162: Model applications 167 tainty inher
Page 163 and 164: Model applications 169 scenario cho
Page 165 and 166: Discussion 171 Finally, the analysi
Page 167 and 168: Discussion 173 bitrarily chosen par
Page 169 and 170: Discussion 175 comparably small imp
Page 171 and 172: Discussion 177 end of the 21st cent
Page 173 and 174: Conclusions 179 Ecological factors
Page 175 and 176: Conclusions 181 species composition
Page 177 and 178: References 183 Begon, M., Harper, J
Page 179 and 180: References 185 Burger, H., 1951. Ho
Page 181 and 182: References 187 Faber, P.J., 1991. A
Page 183 and 184: References 189 Huntley, B. & Birks,
Page 185 and 186: References 191 Leemans, R. & Prenti
Page 187 and 188: References 193 Olson, J.S., 1963. E
Page 189 and 190: References 195 Rudloff, W., 1981. W
Page 191 and 192: References 197 Smith, T.M., Leemans
Page 193 and 194: References 199 Whittaker, R.H., 195
Page 195 and 196: Appendix 201 II. Derivation of para
Page 197 and 198: Appendix 203 Tab. A-4: Tree species
Page 199 and 200:
Appendix 205 Tab. A-7: Values for m
Page 201 and 202:
Appendix 207 The minimum winter tem
Page 203 and 204:
Appendix 209 Tab. A-11: Shade toler
Page 205 and 206:
Appendix 211 Tab. A-14: Climatic pa
Page 207 and 208:
Appendix 213 IV. Source code of the
Page 209 and 210:
Appendix 215 FROM SimBase IMPORT De
Page 211 and 212:
Appendix 217 END; (* IF *) prevDay
Page 213 and 214:
Appendix 219 PROCEDURE InitializeFW
Page 215 and 216:
Appendix 221 InstallSeparator( fMen
Page 217 and 218:
Appendix 223 FROM FCPFileIO IMPORT
Page 219 and 220:
Appendix 225 modelSp^.p.kHm := sens
Page 221 and 222:
Appendix 227 DeclMV( meanLitt[leafS
Page 223 and 224:
Appendix 229 Swiss Federal Institut
Page 225 and 226:
Appendix 231 (*********************
Page 227 and 228:
Appendix 233 BEGIN WITH sp^ DO d :=
Page 229 and 230:
Appendix 235 Definition module FCPB
Page 231 and 232:
Appendix 237 Purpose Simulation mod
Page 233 and 234:
Appendix 239 END Immobilization; PR
Page 235 and 236:
Appendix 241 CONST lem = 3; VAR ef:
Page 237 and 238:
Appendix 243 Purpose Provides the b
Page 239 and 240:
Appendix 245 Example of a text file
Page 241 and 242:
Appendix 247 Tab. A-15: Lower end o
Page 243 and 244:
Appendix 249 Tab. A-17: Percentage
Page 245 and 246:
Appendix 251 Tab. A-19: Significant
Page 247 and 248:
Appendix 253 VI. Derivation of para
Page 249 and 250:
Appendix 255 Tab. A-21: Species-spe
Page 251 and 252:
Appendix 257 Tab. A-22 (continued)
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?