dc.contributor.advisor | Scheu, Stefan Prof. Dr. | de |
dc.contributor.author | Maraun, Melanie Mira | de |
dc.date.accessioned | 2013-01-14T15:07:37Z | de |
dc.date.available | 2013-01-30T23:51:03Z | de |
dc.date.issued | 2012-11-12 | de |
dc.identifier.uri | http://hdl.handle.net/11858/00-1735-0000-000D-EF7E-5 | de |
dc.identifier.uri | http://dx.doi.org/10.3249/webdoc-3756 | |
dc.description.abstract | Waldboden-Nahrungsnetze sind komplexe und
heterogene Systeme. Trophische Beziehungen sind aufgrund der
geringen Größe der Bodentiere und deren kryptischer Lebensweise,
sowie des komplexen Gemisches basaler Ressourcen schwer ergründbar.
Das Zersetzersystem wird trotz seiner fundamentalen Rolle in
Zersetzungsprozessen und für das Funktionieren von | de |
dc.format.mimetype | application/pdf | de |
dc.language.iso | eng | de |
dc.relation.ispartofseries | Biodiversity and Ecology Series - B; 7 | |
dc.rights.uri | http://creativecommons.org/licenses/by-nd/3.0/de/ | de |
dc.title | Compartmentalization and energy channels within the soil animal food web investigated by stable isotope (13C and 15N) and fatty acid analyses | de |
dc.type | doctoralThesis | de |
dc.title.translated | Kompartimentierung und Energie-Kanäle im Bodentier-Nahrungsnetz untersucht mittels Isotopen- und Fettsäuremuster-Analyse | de |
dc.contributor.referee | Scheu, Stefan Prof. Dr. | de |
dc.date.examination | 2012-02-09 | de |
dc.subject.dnb | 000 Allgemeines, Wissenschaft | de |
dc.subject.gok | WA 000 | de |
dc.description.abstracteng | Forest soil food webs are complex and
heterogeneous systems. Trophic relationships are hidden from direct
observation due to small size of soil animals, cryptic habitat and
complex mixtures of basal resources that are not easily separable.
Despite the fundamental role of aboveground-belowground feedbacks
and the major importance of decomposition processes for ecosystem
functioning, the decomposer subsystem has become only recently the
subject of ongoing research. In this thesis, we investigated the
trophic compartmentalization of the decomposer food web and traced
energy fluxes to different compartments within the food web using
stable isotope analyses of δ15N and δ13C and compound specific 13C
fatty acid analyses. To improve the applicability of fatty acid
analyses for field studies we additionally investigated whether
marker fatty acids for specific food sources are transferred to
higher trophic levels including predators, and we studied the time
span required to detect marker fatty acids in consumers after
consumption of a specific food source as well as the time that
marker fatty acids of the previous diet can be detected after
switching to a different food source. In our first study (Chapter
2) we depicted the trophic compartmentalization of the soil animal
food web using the natural variation of δ15N and δ13C in basal
resources and soil animals. We showed that the trophic compartment
of primary decomposers utilizing leaf litter directly is
comparatively small and hypothesized that it is of minor importance
for the decomposer food web. The largest compartment comprised
secondary decomposers presumably feeding on ectomycorrhizal fungi
and predators. Due to similar δ13C signatures of primary
decomposers and ectomycorrhizal fungi, we were not able to separate
predators preying on primary decomposers from ectomycorrhizal
fungal feeders and therefore could not further resolve feeding
strategies within this largest compartment of the soil animal food
web. By supplying specific and relative markers for bacteria, fungi
and plants, fatty acid analysis was potentially applicable to
obtain a finer resolution of feeding strategies within trophic
compartments. To verify trophic transfer of marker fatty acids from
basal resources to higher trophic levels including predators, we
conducted a laboratory experiment (Chapter 3) in which we fed two
major predators, the centipede Lithobius forficatus and the spider
Pardosa lugubris, with the collembolan Heteromurus nitidus kept on
different diets, including fungi, bacteria and tree leaves. Marker
fatty acids for the respective diets were transferred over three
trophic levels to predators; and predators could reliably be
assigned to specific basal resources according to their fatty acid
profiles, suggesting that fatty acid analysis is adequate for the
analysis of whole food webs. In another laboratory experiment
(Chapter 4) we investigated physiological parameters of fatty acid
metabolism, such as the chronological change of fatty acid
biomarkers in collembolans when switched between different food
sources and the change of fatty cid biomarkers during starvation.
Fatty acids typical for a specific diet were already present in the
neutral lipids of consumers after one day, and were still
detectable 14 days after switching to a different diet. During
starvation, there were only minor changes in fatty acid
composition, with marker fatty acids being still detectable in
sufficient amounts after 14 days of food deprivation. Hence, fatty
acid analyses provide a reliable and integrative measure of dietary
composition, even for short and intermediate time intervals. After
verifying the applicability of fatty acid analyses for food web
analysis, we conducted a field study (Chapter 5) in the frame work
of the Swiss Canopy Crane Project, where the tree crowns of a
mature temperate forest are labeled with CO2 depleted in 13C. By
employing a leaf litter exchange experiment, we were able to
separate carbon fluxes originating from aboveground via leaf litter
and from belowground via roots/root exudates. Compound specific 13C
fatty acid analyses of leaf litter, soil, roots and soil animals in
combination with the application of marker fatty acids for specific
food sources allowed to separate energy fluxes through major
channels of the decomposer food web, such as the ectomycorrhizal
vs. saprotrophic fungi channel and the bacterial channel based on
leaf litter or root exudates. Our findings suggest that root
derived carbon is of major importance for the soil animal food web
and that it mainly enters the food web via feeding on
ectomycorrhizal fungi. In contrast to previous assumptions that
forest soil food webs are mainly supported by the fungal energy
channel, we also found considerable fluxes of energy through the
bacterial channel, with all investigated predators containing
significant amounts of bacterial marker fatty acids. Since systems
based on multiple pathways of energy fluxes are assumed to be more
stable, the partitioning between the fungal and bacterial channel
presumably contributes to food web stability. By identifying
trophic compartments and by tracing energy fluxes via different
energy channels, results of this thesis represent major advances in
the understanding of soil animal food web structure and
functioning. | de |
dc.contributor.coReferee | Tscharntke, Teja Prof. Dr. | de |
dc.contributor.thirdReferee | Brose, Ulrich Prof. Dr. | de |
dc.subject.topic | Biology (incl. Psychology) | de |
dc.subject.ger | Bodentiere | de |
dc.subject.ger | Nahrungsnetze | de |
dc.subject.ger | Fettsäuremusteranalyse | de |
dc.subject.ger | Bakterien | de |
dc.subject.ger | Pilze | de |
dc.subject.eng | Soil animals | de |
dc.subject.eng | fatty acid analysis | de |
dc.subject.eng | stable isotope analysis | de |
dc.subject.eng | 15N | de |
dc.subject.eng | 13C | de |
dc.subject.eng | food web | de |
dc.subject.eng | energy channels | de |
dc.subject.eng | bacteria | de |
dc.subject.eng | fungi | de |
dc.subject.bk | 42 - Biologie | de |
dc.identifier.urn | urn:nbn:de:gbv:7-webdoc-3756-9 | de |
dc.identifier.purl | webdoc-3756 | de |
dc.affiliation.institute | Biologische Fakultät | de |
dc.identifier.ppn | 737897678 | de |
dc.identifier.doi | 10.3249/webdoc-3756 | |