Pedogenic carbonates in loess [Elektronische Ressource] : formation rates, formation conditions and source apportionment assessed by isotopes and molecular proxies / vorgelegt von Martina Gocke

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1 Pedogenic carbonates in loess formation rates, formation conditions and source apportionment assessed by isotopes and molecular proxies Dissertation zur Erlangung des Grades Doktor der Naturwissenschaften (Dr. rer. nat.) an der Fakultät für Biologie / Chemie / Geowissenschaften der Universität Bayreuth vorgelegt von Martina Gocke (Dipl.-Geologin) geb. am 06.06.1981 in Erlangen Erstgutachter: Prof. Dr. Yakov Kuzyakov Bayreuth, Juli 2010 2 Die Arbeiten zur vorliegenden Dissertation wurden im Zeitraum von Juni 2007 bis Juli 2010 an der Universität Bayreuth unter der Leitung von Prof. Y. Kuzyakov (Abteilung für Agrarökosystemforschung, Universität Bayreuth) durchgeführt. Vollständiger Abdruck der von der Fakultät für Biologie, Chemie und Geowissenschaften der Universität Bayreuth genehmigten Dissertation zur Erlangung des akademischen Grades Doktor der Naturwissenschaften (Dr. rer. nat.). Amtierender Dekan: Prof. Dr. Stephan Clemens Tag des Einreichens der Dissertation: 27. Juli 2010 Tag des wissenschaftlichen Kolloquiums: 29. Oktober 2010 Prüfungsausschuss: Prof. Dr. Yakov Kuzyakov (Erstgutachter) Prof. Dr. Ludwig Zöller (Zweitgutachter) Prof. Dr. Bernd Huwe (Vorsitzender) Prof. Dr. Britta Planer-Friedrich PD Dr.
Publié le : vendredi 1 janvier 2010
Lecture(s) : 31
Source : D-NB.INFO/1009954679/34
Nombre de pages : 199
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1
Pedogenic carbonates in loess

formation rates, formation conditions and source apportionment
assessed by isotopes and molecular proxies



















Dissertation
zur Erlangung des Grades
Doktor der Naturwissenschaften
(Dr. rer. nat.)
an der Fakultät für Biologie / Chemie / Geowissenschaften
der Universität Bayreuth



vorgelegt von

Martina Gocke (Dipl.-Geologin)
geb. am 06.06.1981 in Erlangen

Erstgutachter: Prof. Dr. Yakov Kuzyakov

Bayreuth, Juli 2010
2
Die Arbeiten zur vorliegenden Dissertation wurden im Zeitraum von Juni 2007 bis Juli 2010
an der Universität Bayreuth unter der Leitung von Prof. Y. Kuzyakov (Abteilung für
Agrarökosystemforschung, Universität Bayreuth) durchgeführt.

Vollständiger Abdruck der von der Fakultät für Biologie, Chemie und Geowissenschaften der
Universität Bayreuth genehmigten Dissertation zur Erlangung des akademischen Grades
Doktor der Naturwissenschaften (Dr. rer. nat.).

Amtierender Dekan: Prof. Dr. Stephan Clemens
Tag des Einreichens der Dissertation: 27. Juli 2010
Tag des wissenschaftlichen Kolloquiums: 29. Oktober 2010

Prüfungsausschuss:
Prof. Dr. Yakov Kuzyakov (Erstgutachter)
Prof. Dr. Ludwig Zöller (Zweitgutachter)
Prof. Dr. Bernd Huwe (Vorsitzender)
Prof. Dr. Britta Planer-Friedrich
PD Dr. Markus Fuchs

3
In Memoriam
Benni
I
Index of contents

Index of tables VII
Index of figures VIII
Abbreviations XII

Summary XIII
Zusammenfassung XV

I Extended Summary

1 Introduction 1
1.1 Object of research 1
1.2 Pedogenic carbonates in paleoenvironmental studies 1
1.3 Previous approaches to estimate rates of pedogenic carbonate formation and
accumulation 4
1.4 Definition of the term ‘recrystallization’ 5
1.5 Objectives 5
2 Methodological considerations: the isotopic exchange approach 6
2.1 Labeling procedure without plants 7
2.2 Labeling procedure with plants 8
2.3 Sampling and analyses 8
2.4 Calculation of recrystallization rates and periods 9
3 Results and discussion 10
14 133.1 Suitability of C vs. C tracers for accurate quantification of recrystallization
(Studies 1, 2) 10
3.2 Effect of environmental factors on CaCO recrystallization rates 11 3
3.2.1 Soil CO concentration (Study 1) 11 2
3.2.2 Plant species (Study 3) 13
3.2.3 Distance to the root surface (Studies 3, 4) 14
3.2.4 Temperature (Study 4) 15
3.3 Recrystallization periods (Studies 1, 3, 4) 16
3.4 Pedogenic carbonate formation: recrystallization vs. migration (Study 5) 19
3.5 Rhizoliths in loess: implications for paleoenvironmental studies 21
3.5.1 Carbon isotope composition and micromorphology (Study 6) 22
3.5.2 Lipid composition of root remains and loess OM (Study 7) 23
4 Conclusions and outlook 25
5 Contribution to the included manuscripts 27
References 29




II
II Cumulative publications and manuscripts

Study 1: Effect of CO concentration on the initial recrystallization rate of 2
14 13pedogenic carbonate – Revealed by C and C labeling 36
Abstract 37
1 Introduction 37
2 Material and methods 39
2.1 Loess 39
2.2 Experiment layout 39
2.3 Labeling and sampling 39
142.4 C analysis 41
132.5 δ C sample analysis 41
14 132.6 C and C calculation and statistical analysis 41
3 Results 42
143.1 C distribution between the C pools 42
143.2 CaCO recrystallization rates and periods calculated based on C incorporation 43 3
133.3 δ C values of loess carbonate and resulting recrystallization rates 45
4 Discussion 46
4.1 Isotopic exchange approach 46
144.2 C distribution and equilibria between C pools 46
4.3 Recrystallization periods of loess carbonate 47
4.4 Relevance of the estimated recrystallization rates 48
5 Conclusions 50
Acknowledgements 50
References 50

Study 2: Pedogenic carbonate recrystallization assessed by isotopic labeling: a
13 14
comparison of C and C tracers 53
Abstract 54
1 Introduction 54
2 Material and methods 56
2.1 Experiment layout and labeling 56
2.2 Analyses 57
2.3 Calculations 58
3 Results 59
3.1 Recrystallization rates 59
3.2 Periods of CaCO recrystallization 61 3
4 Discussion 62
4.1 Isotopic pulse labeling 62
4.2 Estimated CaCO recrystallization rates 63 3
13 144.3 Precision of C and C approaches 63

III
4.4 Reproducibility and reliability of recrystallization rates, and further advantages
14of the C approach 64
4.5 Plausibility of modeled recrystallization periods 65
5 Conclusions 67
Acknowledgements 67
References 67

Study 3: Carbonate recrystallization in root-free soil and rhizosphere of Triticum
14
aestivum and Lolium perenne estimated by C labeling 70
Abstract 71
1 Introduction 71
2 Material and methods 73
2.1 Plants and growing substrate 73
2.2 Experiment layout and plant growing conditions 73
142.3 C labeling and sampling 74
142.4 C sample analysis 75
2.5 Calculations of carbonate recrystallization rate and statistical analysis 76
3 Results 77
143.1 Budget of assimilated C 77
3.2 Calculated recrystallization rates in rhizosphere and root-free loess 79
4 Discussion 81
144.1 Estimation of CaCO recrystallization rates using the C isotopic exchange 3
approach 81
144.2 Influence of plant species on C dynamics and CaCO recrystallization 82 3
4.3 Effect of root vicinity on recrystallization rates 83
4.4 Extrapolation of CaCO recrystallization rates over longer periods 85 3
5 Conclusions 86
Acknowledgements 86
References 87

Study 4: Pedogenic carbonate recrystallization rates and periods are regulated
by temperature-dependent rhizosphere processes: Relevance for
paleoenvironmental applications 90
Abstract 91
1 Introduction 91
2 Material and methods 93
142.1 Experimental layout and C labeling 93
142.2 Sampling and C analysis 94
2.3 Calculation and statistics 95
3 Results 96
3.1 Amounts of recrystallized CaCO and recrystallization rates 96 3
3.2 Respired CO and dissolved inorganic and organic carbon 97 2
IV
4 Discussion 98
4.1 Influence of temperature on CaCO recrystallization rates 98 3
4.2 Effect of temperature on CaCO recrystallization periods 101 3
4.3 Consequences for paleoenvironmental studies 103
5 Conclusions 104
Acknowledgements 105
References 105

Study 5: Pedogenic carbonate formation: recrystallization vs. migration –
14 109 process rates and periods assessed by C labeling
Abstract 110
110 1 Introduction
2 Materials and methods 113
2.1 Experiment setup 113
142.2 C pulse labeling 115
2.3 Moisture conditions 115
2.4 Sampling and analyses 116
2.5 Calculations and statistical analyses 117
3 Results 118
3.1 Plant biomass and loess moisture 118
143.2 C budget 119
3.3 Rhizosphere CO 120 2
3.4 Secondary CaCO 122 3
4 Discussion 123
144.1 C distribution among C pools and methodological approach 123
4.2 Depth-related distribution and accumulation rate of secondary CaCO 123 3
4.3 Time needed for complete leaching of CaCO from upper horizons 126 3
4.4 Comparison with field conditions 127
5 Conclusions 128
Acknowledgements 128
References 128

Study 6: Carbonate rhizoliths in loess and their implications for
13 14
paleoenvironmental reconstruction revealed by isotope composition: δ C, C 133
Abstract 134
1 Introduction 134
2 Methods 136
2.1 Study site 136
2.2 Sampling 137
2.3 Micromorphology 138
2.4 Elemental analyses 138
132.5 δ C analysis 138
V
2.6 Calculation of secondary carbonate portions 139
2.7 Radiocarbon dating 139
2.8 Calculations and statistics 140
3 Results 140
3.1 Micromorphology of rhizoliths 140
3.2 C und C content of rhizoliths and loess 141 org carb
133.3 Stable carbon isotopic composition (δ C) 141
3.4 Portions of secondary carbonate 143
143.5 Radiocarbon ( C) ages 144
4 Discussion 144
4.1 Stable carbon isotope composition 144
4.2 Radiocarbon ages and rhizolith conservation 145
4.3 Implications for rhizolith formation in loess 146
4.4 Implications of the rhizolith – loess macrotransects 147
4.5 Chronologic implications for paleoenvironmental reconstructions 148
5 Conclusions 149
Acknowledgements 150
References 150

Study 7: Rhizoliths in loess – evidence for post-sedimentary incorporation of
root-derived organic matter in terrestrial sediments as assessed from molecular
proxies 154
Abstract 155
1 Introduction 155
2 Materials and methods 158
2.1 Sampling 158
2.2 Elemental and lipid analyses 158
2.3 Molecular proxies 159
2.3.1 Carbon preference index 159
2.3.2 Average chain length (ACL) 160
2.4 Statistical analyses 160
3 Results and discussion 160
3.1 Bulk carbon and lipid content 160
3.2 Molecular composition 162
3.2.1 FAs 162
3.2.2 Alkanes 166
3.3 Implications for rhizolith formation in loess and possible consequences for
palaeoenvironmental reconstruction 169
4 Conclusions 170
Acknowledgements 171
References 171

VI
Previous own publications 175
Acknowledgements 176
Declaration / Erklärung 179
VII
Index of tables

Table I: Properties of loess from Nussloch, SW Germany, sampled in the open cast mine of
the HeidelbergCement AG (N 49°18’41,1’’, E 8°43’37,2’’). 7
Table II: CaCO recrystallization rates for unplanted (Study 1) and planted loess (Studies 3, 3
4) at various conditions. 16

Table 1-1: Amounts of recrystallized CaCO (% of initial CaCO ) after 4, 16 and 65 days 3 3
14under initial CO concentrations of 380, 5000 and 50,000 ppm, calculated based on C 2
incorporation. SEM in brackets. 43
-1 13 14Table 1-2: Recrystallization rates (day ) calculated based on C and C incorporation.
13SEM in brackets. For C, the recrystallization rate could not be calculated at 380 ppm
CO concentration (or at 5000 ppm CO concentration after a recrystallization period of 2 2
13more than 4 days) because the δ C values of the respective replications were lower than
the value of unlabeled loess. 43
Table 1-3: Calculated periods (rounded up to ten years) necessary for the recrystallization of
95% of initial loess carbonate (for loess containing 29% CaCO ). 95% Confidence 3
intervals of the recrystallization periods are given in brackets. 44

14Table 2-1: CaCO recrystallization rates in rhizosphere and non-rhizosphere (only C) loess 3
13 14calculated based on C and C labeling, derived from loess planted with wheat and
13ryegrass. For ryegrass, the C approach did not provide reasonable results, which is also
reflected in Fig. 2-2. For comparison, ranges of recrystallization rates without plants under
CO concentrations between 380 and 50000 ppm in loess air (Gocke et al., 2010b) are also 2
displayed. 61
Table 2-2: Periods necessary for 99% recrystallization of rhizosphere loess CaCO , 3
13 14calculated based on C and C labeling. Growing seasons of 4 and 6 months were
assumed for wheat and ryegrass, respectively. Data in brackets give the lower and upper
limit of the recrystallization periods, based on upper and lower limit of recrystallization
rates. 62

14Table 3-1: Recrystallization rates calculated based on C incorporated into loess CaCO in 3
80 different treatments.

Table 4-1: Portions of CaCO recrystallized in non-rhizosphere and rhizosphere loess 20 3
days after the first labeling. 97

Table 5-1: Dry biomass of plants (g). Mean values ± SEM, n = 5. 119
14Table 5-2: Total C recovery after subsequent growth of 3 maize plants, each of them for 10
14weeks, in different below- and aboveground pools as percentage of recovered C and
14percentage of input C. 120

Table 6-1: Radiocarbon ages of C and C in a rhizolith sampled 1.3 m below the present carb org
soil surface from the loess-paleosol sequence at Nussloch. 144

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