Microbial immobilisation and turnover of _1hn1_1hn3C and _1hn1_1hn5N labelled substrates and microbial diversity in two arable soils under field and laboratory conditions [Elektronische Ressource] / Louisa Wessels Perelo

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• Publié par: technische_universitat_munchen
• Publié le: 01 janvier 2003
• Nombre de lectures: 19
• Langue: Deutsch
• Poids de l'ouvrage: 2 Mo

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13 15MICROBIAL IMMOBILISATION AND TURNOVER OF C AND N
LABELLED SUBSTRATES AND MICROBIAL DIVERSITY IN TWO
ARABLE SOILS UNDER FIELD AND LABORATORY CONDITIONS






Louisa Wessels Perelo







Dissertation 2003
Technische Universität München
GSF-Forschungszentrum für Umwelt und Gesundheit
Institut für Bodenökologie




13 15
Microbial Immobilisation and Turnover of C and N labelled
Substrates and Microbial Diversity in two Arable Soils under Field and
Laboratory Conditions


Louisa Wessels Perelo


Vollständiger Abdruck der von der Fakultät Wissenschaftszentrum
Weihenstephan für Ernährung, Landnutzung und Umwelt der Technischen
Universität München zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.



Vorsitzender: Univ.-Prof. Dr. B. Hock
Prüfer der Dissertation:
1. Univ.-Prof. Dr. J.C. Munch
2. Univ.-Prof. Dr. I. Kögel-Knabner

Die Dissertation wurde am 07.04.2003 bei der Technischen Universität
München eingereicht und durch die Fakultät Wissenschaftszentrum
Weihenstephan für Ernährung, Landnutzung und Umwelt am 25.06.2003
angenommen.
Index
1 Introduction 1
2 Literature Review 3
2.1 The Significance of Microorganisms in Soil 3
2.2 Estimating C and N Turnover through the Microbial Biomass 4
2.3 Estimating Microbial Diversity 6
3 Material and Methods 9
3.1 Site and Soil Material 9
3.2 Experimental Design 10
3.2.1 Field Experiment 10
3.2.2 Laboratory Experiment 11
3.3 Physical Soil Parameters 12
3.3.1 Maximum Water Holding Capacity 12
3.3.2 Gravimetric Water Content 12
3.4 Microbial Biomass Carbon and Nitrogen 12
3.5 Dissolved Organic Carbon and Dissolved Nitrogen 13
3.6 CO - and N O-Fluxes in the Laboratory Experiment 13 2 2
3.7 Total Carbon and Nitrogen 14
3.8 Isotope Analyses 14
13 15
3.8.1 Analysis of C and N in Solid Samples 14
133.8.2 Analysis of C in Liquid Samples 15
15
3.8.3 Analysis of N in Liquid Samples 15
133.8.4 CO -C in Gaseous Samples 16 2
3.8.5 Calculations 16
3.9 Molecular Microbiological Analyses 18
3.9.1 DNA-Extraction 18
3.9.2 Polyacrylamid Gel Elektrophoresis (PAGE) 19
3.9.3 Denaturing Gradient Gel Electrophoresis (DGGE) 19
3.9.4 Analysis of banding patterns 20
3.10 Statistical Analyses 21
4 Immobilisation and Turnover of Carbon 23
4.1 Results 23
4.1.1 Mineralisation of glucose C and mustard C in the laboratory 23
4.1.2 DOC dynamics following substrate addition 25
4.1.3 Total C content 28
4.1.4 Biomass C dynamics following substrate addition 29
4.1.5 Net turnover times of microbial biomass C 33
4.2 Discussion 33
4.2.1 C mineralisation in the laboratory experiment 33
4.2.2 Microbial biomass C immobilisation and C turnover 34
5 Immobilisation and Turnover of Nitrogen 37
5.1 Results 37
5.1.1 Dynamics of substrate N in soil fractions 37
5.1.2 Biomass N dynamics following substrate addition 41
5.1.3 Net turnover times of microbial biomass N 45
5.2 Discussion 45
5.2.1 Dynamics of substrate N in soil 45
5.2.2 Microbial biomass N immobilisation and N turnover 46
6 Microbial Community Patterns 51
6.1 Results 51
6.1.1 Analysis of genomic DNA using random primer 51
6.1.2 Analysis of 16S rDNA 55
6.2 Discussion 57
7 Summary Discussion 61
7.1 CN turnover and ratios 61
7.2 Field and Laboratory estimates 63
7.3 Microbial diversity and C N turnover 64
7.4 Conclusions 66
8 Summary 69
9 Zusammenfassung 71
10 References 75



1 Introduction
Soil microbial biomass (SMB) represents only 1-5 % of the total C- and N-
pool in soil organic matter (SOM) (Jenkinson and Ladd, 1981; Smith and
Paul, 1990; Sparling, 1985).
However, microorganisms play an essential role in ecosystem functioning
as they are responsible for nutrient cycling, humus formation and building
of soil structure along with many other functions. The microbial biomass is
considered to be a dynamic source and sink of nutrients, and it is the driving
force behind SOM transformations (Burger and Jackson, 2003; Jawson et
al., 1989; Smith, 1994).
Most of the recent research in soil ecology has been done in laboratory
microcosm studies (Kampichler et al., 2001). In spite of the importance of
combining laboratory and field studies (Carpenter, 1996; Verhoef, 1996),
this combination has very rarely been realised in soil-ecological research
(Kampichler et al., 2001).
The work presented here was integrated into the FAM Research Network on
Agroecosystems. The main goals of the FAM are to improve information
about agroecosystems, to develop future strategies for environmentally
compatible land use, and to achieve agricultural productivity and
sustainability (Schroeder et al., 2002). Information about energy and matter
fluxes in the agroecosystem is a central part in achieving these goals. The
present work was realised within the sub-project "CN2: CN-Turnover",
which focuses on measuring and modelling the C- and N-turnover.
Soil microbial C and N immobilisation and turnover were estimated for
soils from a high yield and a low yield area of an agricultural field both
under laboratory and field conditions. The objectives were:
§ to determine if the different yield performance was reflected in
- the size of soil microbial biomass,
- the activity of soil microbial biomass and
- the diversity of soil microbial communities.
§ to clarify whether laboratory estimations agreed well with those under
natural field conditions.
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