Abstracts

Use of plant functional types has a long tradition in ecology from the time that von Humboldt offered the first physiognomic classification of plants based on growth form. In recent years, the application of functional traits in ecological studies increased and a variety of new measuring and statistical methods were developed. Functional groups comprise species with similar traits and thus similar response to environmental pressures and similar effects on ecosystem processes. Therefore, it is expected that they are affected rather by niche similarities than by biogeographic regions. However, the feasibility and applicability of functional groups at global scale and across different regions is still an open question.Sand ecosystems are stress-prone habitats with quite low number of species, characterized by long environmental gradients on relatively small area and high ecological and habitat diversity. Considering these facts, sand ecosystems are a suitable model for ecological research. Furthermore, despite increasing attention to functional traits, the knowledge on functional ecology of sand ecosystems is limited. This thesis contributes to fill the gap on functional ecology of sand dunes by defining cluster-based functional groups of species and functional composition of plant communities across different biogeographic regions. Further, the effect of habitat and climatic region on functional groups and the similarity of sand habitats at species, community and functional level were investigated. Finally, the distribution of photosynthesis types across different sand habitats was examined. To achieve the targets, various sand habitat types (drift lines, mobile dunes, stabilized dunes, salt marshes, semi-wet sand and sandy disturbed habitats) across different climatic regions (Atlantic, Mediterranean, Hyrcanian and Irano-Turanian) were studied. We found that sand ecosystems can be defined by sets of functional groups despite their regional climatic and species pool differences. It provides further support to the idea that classification of functional traits should be applicable to other regions. Based on our trait classification, sand dune ecosystems can be described with three main adaptive strategies among perennials and four strategy types in annuals. Ordination analysis of traits also shows that functional traits of the same habitat assembled together irrespective of their regions. This indicates that plant traits in sand ecosystems are grouped reflecting habitat affiliation rather than regional belonging. Furthermore, we investigate the similarity of sand habitats at species, community and functional level. We found by changing the focus from species to community and to functional level, sand habitats of the same kind represent more similarity across regions. The highest habitat similarity was observed at functional level and the lowest at taxonomic level. The vegetation of all habitats at functional level is considered as azonal vegetation and independent from the climatic region. We found out that theAdvisors/Committee Members: Bergmeier, Erwin (advisor), Bergmeier, Erwin (referee), Leuschner, Christoph (referee), Behling, Hermann (referee), Friedl, Thomas (referee), Waltert, Matthias (referee), Kreft, Holger (referee).