Carbon Allocation between the Canopy and the Root System in the Tropical Tree Ceiba Pentandra

185 Pages·2017·9.79 MB·English

by  Mannerheim Neringa

ETH Library
Carbon Allocation between the
Canopy and the Root System
in the Tropical Tree Ceiba
Pentandra: Transfer Velocity,
Magnitude and Biotic Controls
Doctoral Thesis
Author(s):
Mannerheim, Neringa
Publication date:
2018
Permanent link:
https://doi.org/10.3929/ethz-b-000267469
Rights / license:
In Copyright - Non-Commercial Use Permitted
This page was generated automatically upon download from the ETH Zurich Research Collection.
For more information, please consult the Terms of use.
DISS. ETH NO. 24874

CARBON ALLOCATION BETWEEN THE CANOPY AND THE ROOT
SYSTEM IN THE TROPICAL TREE CEIBA PENTANDRA:
TRANSFER VELOCITY, MAGNITUDE AND BIOTIC CONTROLS

A thesis submitted to attain the degree of
DOCTOR OF SCIENCES of ETH ZURICH
(Dr. Sc. ETH Zurich)

presented by
NERINGA MANNERHEIM

M. Sc., Vilnius Gediminas Technical University

born on 18.11.1986
citizen of Lithuania

accepted of the recommendation of
Prof. Dr. Nina Buchmann
Prof. Dr. José Grünzweig
Prof. Dr. Daniel Epron

2018

Table of contents
Table of contents
Table of contents ................................................................................................................................... i
Abstract ............................................................................................................................................... iii
Zusammenfassung .............................................................................................................................. vii
General introduction......................................................................................................................... 1
1.1 Reproducibility of scientific studies.......................................................................................... 1
1.2 The use of stable isotopes in plant ecology ............................................................................... 5
1.3 Carbon allocation in plants ....................................................................................................... 9
1.4 Sink and source relationship ................................................................................................... 11
1.5 Objectives ............................................................................................................................... 13
1.6 Thesis outline .......................................................................................................................... 14
1.7 References ............................................................................................................................... 15
Genotypic variability enhances the reproducibility of an ecological study ................................... 19
2.1 Introduction ............................................................................................................................. 21
2.2 Methods ................................................................................................................................... 24
2.3 Results ..................................................................................................................................... 32
2.4 Discussion ............................................................................................................................... 40
2.5 Acknowledgements ................................................................................................................. 44
2.6 References ............................................................................................................................... 44
2.7 Appendix A ............................................................................................................................. 47
Measurement precision and memory effects of high enrichment 13C and 15N tracer samples ....... 57
3.1 Introduction ............................................................................................................................. 58
3.2 Material and methods .............................................................................................................. 60
3.3 Results and discussion ............................................................................................................ 64
3.4 Conclusions ............................................................................................................................. 70
3.5 Acknowledgements ................................................................................................................. 71
3.6 References ............................................................................................................................... 71
3.7 Appendix B ............................................................................................................................. 74
Carbon allocation to the root system of tropical Ceiba pentandra using 13C pulse-labelling in an
aeroponic facility ............................................................................................................................... 77
4.1 Introduction ............................................................................................................................. 78
4.2 Methods ................................................................................................................................... 82
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4.3 Results .................................................................................................................................... 92
4.4 Discussion ............................................................................................................................ 106
4.5 Conclusions .......................................................................................................................... 111
4.6 Acknowledgements .............................................................................................................. 111
4.7 References ............................................................................................................................ 111
4.8 Appendix C........................................................................................................................... 117
Carbon allocation belowground in the tropical tree Ceiba pentandra is controlled by sink strength
......................................................................................................................................................... 125
5.1 Introduction .......................................................................................................................... 126
5.2 Methods ................................................................................................................................ 127
5.3 Results .................................................................................................................................. 135
5.4 Discussion ............................................................................................................................ 146
5.5 Conclusions .......................................................................................................................... 150
5.6 Acknowledgements .............................................................................................................. 150
5.7 References ............................................................................................................................ 150
5.8 Appendix D .......................................................................................................................... 154
General discussion ........................................................................................................................ 159
Acknowledgements ......................................................................................................................... 169

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Abstract
Abstract
Tropical forests largely contribute to the global carbon (C) cycle and strongly regulate
regional and global climate. They are responsible for one-third of the global terrestrial gross
primary productivity and store large amounts of C in their biomass. Climate change is
currently threatening all terrestrial ecosystems and especially tropical forests. Despite the
important role of tropical forest ecosystems in uptake and storage of atmospheric carbon
dioxide (CO ), C dynamics of tropical tree species remain poorly investigated. Although tree
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root systems contribute greatly to terrestrial C cycling, precise estimates of the contribution
of roots to the terrestrial C cycle still lack for most ecosystems.
The sink and source relationship is a key factor driving C uptake from the atmosphere and
allocation within plant tissues. Understanding the control of this relationship has a potential
for improving plant productivity in forestry and crop sciences. The influence of aboveground
sink (fruit) and source (leaf) activity on C partitioning has been studied in several woody
plant species; however, the contribution of the root system in the control of C allocation is
still unclear. The inaccessibility of the root system greatly contributes to this issue.
This thesis consists of six chapters. The main scientific questions of this thesis were
addressed in Chapters 4 and 5. In Chapter 2, we tested whether a study design with a
controlled systematic variability in ecological microcosm can improve reproducibility among
and within laboratories. 14 laboratories were provided with identical protocols, soil and
seeds of grass Brachypodium distachyon and legume Medicago truncatula. During the
experiment, 72 pots were assigned to six controlled systematic variability groups that
contained various combinations of soil homogeneity and plant genotypes. Combined data
analysis revealed that the introduction of genotypes leads to lower among-laboratory
variability and may be used as a solution for improving the reproducibility of ecological
studies performed in controlled environments.
In Chapter 3, we were looking for methodological solutions to evaluate memory effect and
improve measurement precision of high enrichment 15N and 13C tracer sample. We tested
whether tracer sample dilution, arranged sample positioning and frequent use of natural
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isotopic abundance materials improve measurements precision of highly enriched biomass
samples up to +18000 mUr. Frequent use of natural isotopic abundance materials and
arranged sample positioning increased the precision of tracer samples, but had a negative
effect on the inter-laboratory standards precision. 15N and 13C tracer sample dilution only
slightly improved measurement precision, nonetheless, pure and diluted samples were
highly related. We conclude that highly enriched tracer samples do not require dilution prior
to measurement and that measurement precision can be evaluated and improved by using
natural isotope abundance materials and arranged positioning.
In Chapter 4, we investigated C allocation dynamics to the belowground root system and C
transfer velocity in the tropical tree Ceiba pentandra. We applied 13CO pulse-labelling on
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9-months old C. pentandra saplings grown in a large-scale aeroponic facility in Israel, called
Root laboratory. The 13C pulse was traced in bulk tissue, sugars and starch, with special focus
given to woody and non-woody roots. We found tight coupling between the canopy and
the root system. We calculated a potential maximum C transfer velocity of 2.4 m h-1, while
the mean C transfer velocity to root sugars ranged in between 24 - 34 h. Five days after
pulse-labelling, 27% of 13C taken up by the trees was found in the leaves, 13% in the woody
tissue of the trunk, 6% in the bark, 2% in the root system and a total of 52% was lost. In
addition, we identified sink strength differences within woody and non-woody roots. Sink
strength decreased with the depth of the root system for coarse woody brown roots, while
it increased with root depth for non-woody white roots. These findings with tropical trees
compare well with temperate trees and give new insights into C dynamics between different
root depths and root categories.
In Chapter 5, we performed a sink size manipulation experiment to test whether short-term
C allocation is driven by sink (root) or source (canopy) strength in the tropical tree C.
pentandra. The 13CO pulse-labelling was followed by root removal treatments, and a 13C
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signal was traced into the leaves, woody and non-woody root categories during a 70 h post-
treatment period. Root removal strongly affected C allocation and C recovery in the entire
tree. Trees with lower root to shoot ratios allocated less C to the root system than trees
with higher root to shoot ratios. C allocation to root bulk tissue, sugars, starch and
respiration significantly differed among root categories. In addition, in all studied materials
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Abstract
and compounds (except sugars) C allocation to the roots significantly differed by root depth.
In Chapter 5, we concluded that C allocation to the root system is strongly driven by sink
strength. These findings contribute to a better understanding of the extent the root system
is contributing to the control of C allocation.
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Zusammenfassung
Zusammenfassung
Tropische Wälder stellen einen wichtigen Teil des globalen Kohlenstoffkreislaufs dar und
haben darüber hinaus einen starken Einfluss auf das regionale und globale Klima. Sie sind
für ein Drittel der globalen terrestrischen Primärproduktion verantwortlich und speichern
eine grosse Menge an Kohlenstoff in ihrer Biomasse. Der Klimawandel bedroht alle
terrestrischen Ökosysteme und besonders tropische Wälder. Unabhängig von ihrer
bedeutsamen Rolle in der Aufnahme und Speicherung von atmosphärischem Kohlendiodid
(CO ) sind Kohlenstoffdynamiken von tropischen Baumarten bisher nur wenig erforscht.
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Obwohl Wurzelsysteme von Bäumen einen grossen Teil zum terrestrischen
Kohlenstoffkreislauf beitragen, fehlen präzise Schätzungen für die meisten Ökosysteme.
Das Quellen-Senken Verhältnis beeinflusst die Aufnahme von Kohlenstoff aus der
Atmosphäre und die Allokation innerhalb der Pflanze. Ein besseres Verständnis der
Kontrolle dieser Beziehung kann zur Verbesserung der Pflanzenproduktivität in Agrar- und
Forstwirtschaft beitragen. Der Einfluss der Aktivität oberirdischer Senken (z.B. Frucht) und
Quellen (z.B. Blatt) auf die Kohlenstoffpartitionierung wurde bisher erst in einigen Gehölzen
untersucht. Dennoch ist der Beitrag des Wurzelsystems zur Kontrolle der
Kohlenstoffallokation noch unbekannt, unter anderem weil das Wurzelsystem für
Untersuchungen nicht zugänglich ist.
Diese Doktorarbeit besteht aus sechs Kapiteln, wobei die Hauptfragen dieser Arbeit in den
Kapitel 4 und 5 behandelt werden. Im zweiten Kapitel wurde getestet, ob ein Studiendesign
mit einer systematischen kontrollierten Variabilität in ökologischen Mikrokosmen die
Reproduzierbarkeit zwischen und innerhalb Laboratorien verbessert. Vierzehn Labore
wurden mit identischen Protokollen sowie Bodenproben und Samen der Grasart
Brachypodium distachyon und der Leguminose Medicago truncatula ausgestattet. Während
des Experiments wurden 72 Töpfe sechs kontrollierten systematischen Variabilitätsgruppen
zugeordnet, welche verschiedene Kombinationen von Bodenhomogenität und
Pflanzengenotypen beinhalteten. Eine kombinierte Datenanalyse stellte fest, dass die
Einführung von Genotypen zu einer geringeren Variabilität zwischen Laboren führte und
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