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dc.contributor.author
Meller, Sonia
dc.contributor.supervisor
Frossard, Emmanuel
dc.contributor.supervisor
Luster, Jörg
dc.contributor.supervisor
Frey, Beat
dc.contributor.supervisor
Göttlein, Axel
dc.date.accessioned
2020-06-15T10:42:11Z
dc.date.available
2020-06-13T21:04:01Z
dc.date.available
2020-06-15T10:42:11Z
dc.date.issued
2019
dc.identifier.uri
http://hdl.handle.net/20.500.11850/420232
dc.identifier.doi
10.3929/ethz-b-000420232
dc.description.abstract
Forests dominated by beech (Fagus sylvatica L.) cover a large part of Europe and occur on a wide variety of soils, realizing a broad ecological niche in terms of soil chemical properties including pH, base saturation, and plant-available phosphorus (P) pools in the mineral topsoil. On the other hand, a decrease in foliar P concentrations and a corresponding increase in the nitrogen (N) to P ratio during the last decades all over Europe raised questions about a possible reduction in forest health and productivity due to P limitation. These changes in leaf nutrient status have been attributed to continuing high N deposition and increasing atmospheric carbon dioxide concentrations. Both accelerated tree growth due to high N and carbon (C) input and adverse effects of elevated N on fine root biomass, mycorrhization, and litter mineralization appear to have created a higher need for other nutrients that cannot be met by the supply from the soil. Surprisingly little is known about internal P allocation of beech and its capacity to deal with changing soil P availability in the short-term. Considering the distribution of beech forests on soils encompassing a broad range of nutrient availability, and thus proven ability to adapt to different soil conditions in the long-term, we hypothesized that this tree species exhibits a high phenotypic plasticity allowing it to alter multiple traits in response to local nutrient availability leading to adaptive acclimation and resulting in a phenotype tailored for local soil conditions. This PhD-thesis aimed to investigate acclimation of beech from high to low and from low to high soil P availability in terms of plant internal P cycling and plant-soil interactions in the rhizosphere. For this purpose, we grew two groups of 12–15-year-old beech saplings originating from sites with high and low soil P availability in mineral soil (Bh/Bv horizon) from their own site and soil from the other site in rhizoboxes for two years in the greenhouse. We assumed that our saplings were adapted to their soil of origin and that their P nutritional status thus reflected the nutrient availability in the soil of origin. First, we assessed the plasticity of mass and P allocation in the beech saplings aiming to identify the traits most responsive to current soil conditions. After two growing seasons, P concentrations in leaves and stem, as well as mass allocation to leaves and fine roots were affected by both soil and plant origin. By contrast, P allocation to leaves and fine roots, as well as P concentrations in fine roots, were determined almost entirely by the experimental soil. Independent of the P nutritional status defined as average concentration of P in the whole plant, which still clearly reflected the soil conditions at the site of plant origin, P allocation to leaves was a particularly good indicator of P availability in the experimental soil. Furthermore, the high plasticity of this plant trait was indicated by a large difference between plants growing in the two experimental soils. This suggests a strong ability of beech to alter resource allocation in response to specific soil conditions. Second, we investigated the plasticity of root traits and rhizosphere properties of young beech trees from populations, that are adapted to either high or low nutrient supply, when growing in soils differing in their fertility. Fine root traits related to growth (biomass, length), architecture (branching) and morphology (diameter) responded strongly to the properties of the soil. This response was modified by an effect of provenance, that was consistent with an influence of the plant status in those nutrients, which were not in sufficient supply in the soil. However, an additional genotypic difference in the sensitivity of the beech saplings to different soil nutrient supply could not be excluded. Fine root parameters normalized for length, mass, or volume (root tip density and frequency, specific root length and area, root tissue density) did not differ among the treatments. Differences in mycorrhizal colonization and rhizosphere parameters related to phosphorus mobilization potential (pH, an abundance of organic acid anions, phosphatase activity) were small and mainly determined by the soil. Provenance had only a minor modifying effect, possibly due to differences in the ability to transfer carbon compounds from the shoot to the root and the fungal partner. Our results indicate the high plasticity of young beech trees to adapt root growth, architecture, and morphology to different soil nutrient supply, thereby also taking into account internal nutrient reserves. Third, amplicon sequencing was used to assess to which degree beech saplings with a different P nutritional status can shape their rhizosphere microbial community along the root axis. After the first growing season, we determined the community composition and relative abundance of bacteria and fungi in bulk soil and different zones of the rhizosphere of freshly grown roots defined by root segments potentially differing in their functionality (root tip, elongation zone, side root, old roots). We found that soil was the main factor determining microbial diversity and composition irrespective of plant origin and zone. Overall, OTU (operational taxonomic unit; an operational term for groups of closely related biota) numbers of bacteria and fungi, correlating well with soil microbial biomass, were higher in the soil with high P availability than in the soil with low P availability. Based on the relative abundance of OTUs, the bacterial and fungal communities in the different rhizosphere zones grouped distinctly indicating a succession from bulk soil to older roots via root tip, elongation zone, and side root zone demonstrating the often-postulated gradual development of rhizosphere microbial communities along the root axis. There was a significant effect of plant nutritional status on bacterial community diversity (beta diversity) differentiating elongation zone and on fungal community in the elongation and root tip zones. Furthermore, local average microbial species diversity (alpha diversity quantified with Shannon index) in the bulk soil and active rhizosphere zones (root tip, elongation zone) was higher in treatments with beech saplings acclimating to altered soil P availability than in treatments with plants adapted to the respective conditions. The only indication of a plant effect potentially offering an advantage concerning P nutrition, was a higher relative abundance of the bacterial order Solibacterales, potentially important for the mobilization of inorganically bound P, in some zones in treatments with beech saplings exhibiting a low P nutritional status. We conclude that overall, the P nutritional status of beech saplings had only a small influence on the soil microbial community in the rhizosphere. However, the related plant effects were strongest in the rhizosphere of the elongation zone, i.e., the potentially most active root segment in terms of root exudation. This Ph.D. thesis demonstrated that beech saplings are capable of fast acclimation to changes in soil P availability involving alterations of internal P allocation patterns, root architecture, and interactions with local ectomycorrhizal fungi and bacteria in the rhizosphere. Comparing the results for treatments representing plants adapted to low or high soil P availability and for treatments representing plants with a given P nutritional status acclimating to altered soil P availability suggests that alterations of the same sets of multiple traits are involved in both long-term adaptation and short-term acclimation to given soil conditions. Together, the traits define respective growth strategies of adapted plants, i.e., a conservative strategy in soils with low P availability prioritizing nutrient storage and internal recycling and thus limiting losses, and a strategy prioritizing fast growth in soils with high P availability leading to high P acquisition rates but also high losses. These strategies can be considered analogous to and being part of “recycling” and “acquiring” strategies on the ecosystem level. However, our results also indicate that during the first phases of acclimation to lower soil P availability, beech saplings with a high P nutritional status use their reserves to grow as much as possible.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
acclimation
en_US
dc.subject
Fagus sylvatica
en_US
dc.subject
forest health
en_US
dc.subject
phosphorus allocation
en_US
dc.subject
phosphorus nutritional status
en_US
dc.subject
soil phosphorus availability
en_US
dc.subject
rhizosphere microbial community
en_US
dc.subject
root traits
en_US
dc.subject
root zones
en_US
dc.subject
root exudation
en_US
dc.subject
phenotypic plasticity
en_US
dc.subject
beech
en_US
dc.title
Plasticity of beech saplings (Fagus sylvatica L.) In response to soil P availability
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
dc.date.published
2020-06-15
ethz.size
166 p.
en_US
ethz.code.ddc
DDC - DDC::5 - Science::550 - Earth sciences
en_US
ethz.identifier.diss
26520
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02350 - Dep. Umweltsystemwissenschaften / Dep. of Environmental Systems Science::02703 - Institut für Agrarwissenschaften / Institute of Agricultural Sciences::03427 - Frossard, Emmanuel / Frossard, Emmanuel
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02350 - Dep. Umweltsystemwissenschaften / Dep. of Environmental Systems Science::02703 - Institut für Agrarwissenschaften / Institute of Agricultural Sciences::03427 - Frossard, Emmanuel / Frossard, Emmanuel
en_US
ethz.relation.hasPart
https://doi.org/10.3389/fpls.2019.00744
ethz.date.deposited
2020-06-13T21:04:11Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2020-06-15T10:42:46Z
ethz.rosetta.lastUpdated
2022-03-29T02:24:49Z
ethz.rosetta.versionExported
true
ethz.COinS
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