The effects of long-term Free Air CO_1tn2 Enrichment (FACE) on soil aggregation, soil carbon input, and ecosystem CO_1tn2 dynamics in a temperate grassland ecosystem [Elektronische Ressource] / vorgelegt von Katharina Lenhart

Sujets

• Biologie

Informations

• Publié par: justus-liebig-universitat_giessen
• Publié le: 01 janvier 2009
• Nombre de lectures: 19
• Langue: Deutsch
• Poids de l'ouvrage: 2 Mo

Extrait

The effects of long-term Free Air CO 2
Enrichment (FACE) on soil aggregation, soil
carbon input, and ecosystem CO dynamics in 2
a temperate grassland ecosystem






Inauguraldissertation

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

der naturwissenschaftlichen Fachbereiche der
Justus-Liebig-Universität Gießen

vorgelegt von
Katharina Lenhart

Gießen, im September 2008


Dekan: Prof. Dr. Peter R. Schreiner

Erster Gutachter: Prof. Dr. Dr. h.c. Hans-Jürgen Jäger

Zweiter Gutachter: Prof. Dr. Christoph Müller

Tag der mündlichen Prüfung:

22. Dezember 2008 Erklärung

Hiermit erkläre ich, dass ich die vorgelegte Dissertation selbstständig und ohne unerlaubte
fremde Hilfe und nur mit den Hilfen angefertigt habe, die ich in der Dissertation angegeben
habe.
Alle Textstellen, die wörtlich oder sinngemäß aus veröffentlichten Schriften entnommen sind,
und alle Angaben, die auf mündlichen Auskünften beruhen, sind als solche kenntlich
gemacht.
Bei den von mir durchgeführten und in der Dissertation erwähnten Untersuchungen habe ich
die Grundsätze guter wissenschaftlicher Praxis, wie sie in der „Satzung der Justus-Liebig-
Universität Gießen zur Sicherung guter wissenschaftlicher Praxis“ niedergelegt sind,
eingehalten.


Gießen, den 26. September 2008 Table of contents I
Table of contents
List of tables……………………………………………………………..………………… III
List of figures……………………………………………………………………...…..……IV
Abbreviations…………………………………….……………………………….……… VI
Abstract………………...……………………………………………………………….….XII
Kurzfassung…………………………………………………………………………….…..IX

1 Introduction _________________________________________ 1
1.1 Climate change and grassland ecosystems ........................................... 1
1.2 Effects of elevated CO on ecosystem C dynamics ............................... 2 2
1.2.1 Grassland FACE experiments................................................................ 2
1.2.2 Ecosystem C balance ............................................................................ 3
1.2.3 Soil aggregate structure......................................................................... 4
1.2.4 Soil and ecosystem respiration and its components............................... 6
1.3 Objectives of this study............................................................................ 8
2 Materials and methods ________________________________ 9
2.1 Site description......................................................................................... 9
2.2 Air temperature, precipitation, and soil data .........................................10
2.2.1 Air temperature and precipitation ..........................................................10
2.2.2 Soil texture............................................................................................12
2.2.3 Bulk density ..........................................................................................12
2.2.4 Soil moisture.........................................................................................13
2.3 Soil and plant biomass sampling and analysis .....................................14
2.3.1 Soil sampling ........................................................................................14
2.3.2 Soil aggregate fractionation ..................................................................14
2.3.3 Plant biomass .......................................................................................16
132.3.4 Analysis of C signature and SOC content...........................................17
2.3.5 Calculations ..........................................................................................17
2.4 Gas sampling and analysis .....................................................................19
2.4.1 Gas sampling........................................................................................19
132.4.2 Analysis of δ C signature and CO concentration.................................20 2
2.4.3 Separation of soil and ecosystem respiration into its components.........20
2.5 Statistical analysis...................................................................................25
3 Results ____________________________________________ 27
3.1 Air temperature, precipitation, and soil moisture..................................27
3.2 Plant biomass ..........................................................................................30
133.2.1 δ C signature of above and belowground biomass ..............................30
3.2.2 Root biomass yield................................................................................32
3.3 Soil aggregate structure..........................................................................34
3.3.1 Distribution of aggregates in the soil profile...........................................34
3.3.2 Soil aggregation changes between 1998 and 2007...............................35 Table of contents II
3.3.3 Effect of elevated CO on soil aggregation ...........................................36 2
133.4 Soil organic carbon content and δ C signature under ambient and
elevated CO ............................................................................................38 2
3.4.1 SOC content.........................................................................................38
3.4.2 Effects of elevated CO on SOC content ..............................................44 2
133.4.3 δ C signature of SOC in bulk soil and the soil aggregate fractions.......45
3.5 Soil C input in the CO enriched plots ...................................................49 2
3.5.1 Fraction of new C .................................................................................49
3.5.2 Input of new C ......................................................................................50
3.5.3 Input of new C into free and macroaggregate-associated
microaggregates...................................................................................53
3.6 Soil air CO and ecosystem respiration.................................................55 2
133.6.1 Annual dynamics of ecosystem respiration and δ C and CO 2
concentration in soil air.........................................................................55
3.6.2 Partitioning of R into autotrophic and heterotrophic components.......65 soil
3.6.3 Partitioning of R ................................................................................69 eco
4 Discussion_________________________________________ 73
4.1 Effects of elevated CO on the soil aggregate structure.......................73 2
4.2 Effects of elevated CO on the soil C content .......................................77 2
4.3 Soil C input under elevated CO .............................................................83 2
4.4 Effects of elevated CO on the autotrophic and heterotrophic 2
components of soil and ecosystem respiration....................................91
5 Conclusions and outlook _____________________________ 99
6 References________________________________________ 101
7 Appendix _________________________________________ 116
7.1 Date of aboveground biomass clipping...............................................116
7.2 Drying-Wetting Cycles between 1997 and 2004 ..................................116
7.3 List of gas samples ...............................................................................116
7.4 Bulk density...........................................................................................121

List of tables III
List of Tables

13Tab. 2.1 δ CO of tank-CO and atmospheric CO in the CO -enriched plots ........10 2 2 2 2
Tab. 2.2 Soil texture and pH in the soil profile ........................................................12
Tab. 3.1 Mean air temperatures (T ) and temperature changes.............................27 air
13Tab. 3.2 Predicted and measured δ C signature of plants .....................................30
13Tab. 3.3: δ C signature of aboveground plant biomass..........................................31
13Tab. 3.4 Effect of depth on δ C signature of root biomass .....................................32
Tab. 3.5 Differences in root biomass between the CO treatments .........................33 2
Tab. 3.6 Relative changes in soil aggregation.........................................................36
Tab. 3.7 Average changes in SOC content between April 1998 and 2004..............39
Tab. 3.8 Changes in total SOC under ambient atmospheric CO conditions ...........39 2
Tab. 3.9 Area-related changes in SOC of several soil fractions ..............................41
Tab. 3.10 Fraction of new C in several soil aggregate fractions after 8 years of
elevated [CO ] +20%................................................................................49 2
Tab. 3.11 Fraction of new C in several soil aggregate fractions after 8 years of
elevated [CO ] +30%................................................................................50 2
Tab. 3.12 Rate of C input per year under [CO ] +20% ............................................51 2
Tab. 3.13 Rate of C input per year under [CO ] +30% ......