| dc.contributor.advisor | Scheu, Stefan Prof. Dr. | |
| dc.contributor.author | Zieger, Sarah Lorain Janice | |
| dc.date.accessioned | 2016-10-26T09:46:57Z | |
| dc.date.available | 2016-10-26T09:46:57Z | |
| dc.date.issued | 2016-10-26 | |
| dc.identifier.uri | http://hdl.handle.net/11858/00-1735-0000-002B-7C4C-C | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-5926 | |
| dc.language.iso | eng | de |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject.ddc | 570 | de |
| dc.title | Trophic structure of soil animal food webs of deciduous forests as analyzed by stable isotope labeling | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Scheu, Stefan Prof. Dr. | |
| dc.date.examination | 2016-01-22 | |
| dc.description.abstracteng | Forest soil invertebrates are extremely diverse and form complex food webs. Trophic interactions are concealed from direct observation by the heterogeneous soil system and small size of soil invertebrates and their basal resources such as soil microorganisms. The soil system is connected to plant via roots and leaf litter. Tree species identity is known to affect soil animal communities and energy fluxes. To analyze energy fluxes from the above- to the belowground system stable isotopes are widely used. By using 13C (carbon) and 15N (nitrogen) labeling experiments, I analyzed the contribution of litter- and root-derived resources to soil animal nutrition. European beech (Fagus sylvatica) and common ash (Fraxinus excelsior), two common tree species of the temperate zone, largely differing in traits such as litter quality and mycorrhizal association, were chosen.
In Chapter 2 the incorporation of litter-derived resources into soil mites was investigated by using beech and ash leaf litter enriched in 13C and 15N. The two leaf litter species differed in structural compounds with beech leaf litter being high in structural compounds and ash leaf litter being low in structural compounds. Soil mites generally incorporated low amounts of litter-derived C and N, but the incorporation of ash litter C and N exceeded that of beech litter C and N. This was also shown by preference for ash litter by Platynothrus peltifer (Oribatida). Further, soil mite species adapted to deprivation of fast decomposing ash litter by switching diet towards beech litter.
The low contribution of litter-derived resources reinforces the current view, that root-derived resources outweigh litter-derived resources in nourishing soil food webs. Two additional labeling experiments (Chapter 3 and 4) were conducted to investigate the contribution of root-derived resources. By applying CO2 enriched in 13C and immersing leaves in a 15N containing solution aboveground plant parts were labeled and C and N fluxes into soil animals were analyzed. In a field experiment (Chapter 3) soil animals incorporated root-derived N and the incorporation in the beech rhizosphere exceeded that in the ash rhizosphere. A second pulse labeling experiment under controlled conditions in a plant growth chamber confirmed these results. Root-derived N was transferred into soil animal food webs in a species specific way. Some soil animals such as Onychiuridae (Collembola) incorporated high amounts of 15N indicating that they directly fed on roots or root hairs, while the predatory mite Veigaia nemorensis (Gamasina) mainly got access to root-derived N via feeding on secondary decomposers such as Collembola. The distribution of root-derived N in soil animal food webs may have important ecological consequences. By releasing amino acids plant roots could stimulate microbes and thereby soil animals which are then responsible for decomposition processes. Root-derived C was also incorporated into soil animal food webs and the incorporation into soil animals in the beech rhizosphere exceeded that in the ash rhizosphere presumably mediated by the different association with mycorrhiza. Beech is associated with ectomycorrhizal fungi (EMF), while ash is associated with arbuscular mycorrhizal fungi (AMF). In the last study (Chapter 5) the analysis of root-derived C and N combined with fatty acid analysis documented that the Protura species Acerentomon sp. is sucking on EMF.
The results of this thesis indicate that energy fluxes in the food web of beech and ash forests differ markedly. Beech trees produce leaf litter not easily to digest, but release root-derived resources into the rhizosphere which are then incorporated into the soil animal food web. In contrast, ash has easier digestible leaf litter, but the incorporation of root-derived resources are less pronounced as compared to beech. Fast decomposition of ash litter within the first year of litter decay might hamper the positive effect of easily ingestible leaf litter and leads to deprivation of food and habitat later in the year. As this thesis investigated the contribution of litter- and root-derived resources in separate experiments further experiments are needed in which both litter- and root-derived resources are manipulated simultaneously to quantify the contribution of both pathways in fueling soil animal food webs. | de |
| dc.contributor.coReferee | Maraun, Mark Prof. Dr. | |
| dc.subject.eng | soil animal food web | de |
| dc.subject.eng | temperate deciduous forest | de |
| dc.subject.eng | root-derived resources | de |
| dc.subject.eng | stable isotope labeling | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-11858/00-1735-0000-002B-7C4C-C-0 | |
| dc.affiliation.institute | Biologische Fakultät für Biologie und Psychologie | de |
| dc.subject.gokfull | Biologie (PPN619462639) | de |
| dc.identifier.ppn | 871256339 | |