Cyclical succession in semi-arid savannas revealed with a spatial simulation model [Elektronische Ressource] / von Katrin M. Meyer

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Sujets

• Biologie

Informations

• Publié par: friedrich-schiller-universitat_jena
• Publié le: 01 janvier 2006
• Nombre de lectures: 34
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Cyclical succession
in semi-arid savannas revealed with
a spatial simulation model






Dissertation
zur Erlangung des akademischen Grades
doctor rerum naturalium (Dr. rer. nat.)











vorgelegt dem Rat der Biologisch-Pharmazeutischen Fakultät
der Friedrich-Schiller-Universität Jena





von Diplom-Biologin Katrin M. Meyer
geboren am 06. September 1977 in Hamburg




Jena, den 10. Mai 2006



















































































Gutachter:
1.: ..................................................................................................
2.: ..................................................................................................
3.: ..................................................................................................
Tag der Doktorprüfung: .........................................................................
Tag der öffentlichen Verteidigung: ...........................................................



























































A model should be as simple as possible.
But no simpler.

Albert Einstein







I proceeded with the utmost caution, but, with all my care, a small twig caught
hold of my sleeve. While thinking to disengage it quietly with the other hand,
both arms were seized by these rapacious thorns, and the more I tried to extricate
myself, the more entangled I became; till at last it seized hold of the hat also; (…)
In revenge for this ill-treatment, I determined to give the tree a name which
should serve to caution future travellers against allowing themselves to venture
within its clutches.

W.J. Burchell (1782-1863) about Acacia mellifera ssp. detinens
(detinere, Lat. = to detain) Contents

Contents

List of Figures
List of Tables

1 Introduction 1
References 6

2 Multi-proxy evidence for competition between 9
savanna woody species
Abstract 9
Introduction 10
Methods 12
Results 15
Discussion 19
References 22
Appendix 24

3 Big is not better: Small Acacia mellifera shrubs 25
are more vital after fire
Abstract 25
Introduction 26
Methods 27
Results 28
Discussion 30
References 32

4 Determining patch size 34
Abstract 34
Introduction 35
Methods 35
Results and Discussion 37
References 37



Contents






5 SATCHMO: A spatial simulation model of growth, 39
competition, and mortality in cycling savanna
patches
Abstract 39
Introduction 40
Methods 42
Results 59
Discussion 62
References 66
Appendix A 68
Appendix B 69

6 The rhythm of savanna patch-dynamics 70
Abstract 70
Introduction 71
Methods 72
Results 78
Discussion 82
References 85

7 Concluding discussion 88
References 94

Summary 96

Zusammenfassung 98

Acknowledgements
Curriculum vitae


List of Figures

List of Figures



Chapter 2

Fig. 2.1: The univariate O-ring statistic O(h) at different scales h for small 16
and large A. mellifera shrubs (split approach)

Fig. 2.2: Relative frequency distributions of regular patterns at different 16
scales, of negative autocorrelation at different scales, and of the maximum
root length

Fig. 2.3: Relationship between the sum of the canopy diameters of the target 18
shrub and its 4 nearest neighbours and the sum of the distances to the 4
nearest neighbours in the 15 m × 15 m plots


Chapter 3

Fig. 3.1: Relative frequencies of total height of A. mellifera shrubs without 28
regrowth and with regrowth after fire

Fig. 3.2: Relationship between the height of regrowth and the total height of 29
A. mellifera shrubs

Fig. 3.3: Relationship between the length of the longest root and the total 30
height of A. mellifera shrubs


Chapter 4

Fig. 4.1: Example of a bird’s eye view of one of the 15 m × 15 m example 36
plots


Chapter 5

Fig. 5.1: Schematic representation of belowground characteristics of a model 44
shrub competing with a grass tuft and a root from another shrub

Fig. 5.2: Scheduling of the main processes in SATCHMO 45

Fig. 5.3: Simulated shrub canopy cover in % over time with asymptotic 50
regression model

Fig. 5.4: Distribution of relative frequencies of the canopy diameter of 461 61
observed shrubs and all simulated shrubs occurring during 10 runs of 500
simulation years


List of Figures







Chapter 6

Fig. 6.1: An example simulation run of shrub cover dynamics over time 78

Fig. 6.2: Time lags at which significant positive and negative partial 79
autocorrelation of shrub cover occurs for 100 simulations over 500 years

Fig. 6.3: Distribution of relative frequencies of age at death of all shrubs 79
that survived their first year in 10 simulations over 500 years

Fig. 6.4: Absolute frequencies of canopy diameters of all simulated shrubs in 80
three simulation years chosen from one exemplary cycle representing the
initiation phase, the build-up phase, and the break-down phase

Fig. 6.5: Annual precipitation and smoothed shrub cover over time simulated 81
with default parameter values

Fig. 6.6: Relationship between shrub cover at time step t, annual 81
precipitation, and shrub cover at time step t-1 predicted by a linear multiple
regression model

List of Tables

List of Tables



Chapter 2

Table 2.1: Mean and standard deviation of parameters estimated from the 17
competitor removal experiment, the 15 m × 15 m plots, and the
10 m × 10 m plots


Chapter 5

Table 5.1: SATCHMO model parameters 47

Table 5.2: Simulated and observed average annual regrowth length, 60
population size, maximum canopy diameter and shrub thicket diameter