Molecular phylogeography of the European coastal plants Crithmum maritimum L., Halimione portulacoides (L.) Aellen, Salsola kali L. and Calystegia soldanella (L.) R. Br.

The intraspecific phylogeography of four European coastal plants, Crithmum maritimum, Halimione portulacoides, Salsola kali and Calystegia soldanella, was inferred from AFLP and ITS data. Only in C. maritimum, H. portulacoides and S. kali, a spatial genetic structure was revealed. The phylogeographic similarities and dissimilarities of these species include: (1) All three have distinct Black/Aegean and Adriatic Sea clusters. (2) Salsola kali and H. portulacoides show a distinct Atlantic/North Sea/Baltic Sea cluster, while Atlantic and eastern Spanish material of C. maritimum clustered together. (3) In the west Mediterranean, only S. kali forms a single cluster, while both H. portulacoides and C. maritimum display a phylogeographic break in the vicinity of the southern French coast. For S. kali, AFLP and ITS data concur in identifying separate Atlantic, east and west Mediterranean clades. All these patterns are postulated to result from both temperature changes during the last glacial and contemporary sea currents. No geographic AFLP structure was revealed in C. soldanella, both at the range-wide and population level. This was attributed to the remarkable seed dispersal ability of this species and possibly its longevity and clonal growth, preserving a random pattern of genetic variation generated by long-distance seed dispersal over long time periods.

European phylogeography of the coastal plants Cakile maritima Scop. (Brassicaceae) and Eryngium maritimum L. (Apiaceae)

Linear dispersal systems, such as coastal habitats, are well suited for phylogeographic studies because of their low spatial complexity compared to three dimensional habitats. Widely distributed coastal plant species additionally show azonal and often essentially continuous distributions. These properties, firstly, make it easier to reconstruct historical distributions of coastal plants and, secondly, make it more likely that present distributions contain both Quaternary refugia and recently colonized areas. Taken together this makes it easier to formulate phylogeographic hypotheses. This work investigated the phylogeography of Cakile maritima and Eryngium maritimum, two species growing in sandy habitats along the north Atlantic Ocean and the Mediterranean Sea coasts on two different spatial scales using AFLP data. The genetic structure of these species was investigated by sampling single individuals along most of their distributions from Turkey to south Sweden. On a regional scale the population genetic structure of both species was also studied in detail in the Bosporus and Dardanelles straits, the Strait of Gibraltar and along a continuous stretch of dunes in western France. Additionally, populations of C. maritima were investigated in the Baltic Sea/Kattegat/North Sea area. Over the complete sampling range the species show both differences and similarities in their genetic structure. In the Mediterranean Sea, both species contain Aegean Sea/Black Sea and west Mediterranean clusters. Cakile maritima additionally shows a clustering of Ionian Sea/Adriatic Sea collections. Further, both species show a subdivision of Atlantic Ocean/North Sea/Baltic Sea material from Mediterranean. Within the Atlantic Ocean group, C. maritima from the Baltic Sea and the most northern Atlantic localities form an additional cluster while no such substructure was found in E. maritimum. In all three instances where population genetic investigations of both species were performed in the same area, the results showed almost complete congruency of spatial genetic patterns. In the Aegean/Black Sea/Marmara region a subdivision of populations into a Black Sea, a Sea of Marmara and an Aegean Sea group is shared by both species. In addition the Sea of Marmara populations are more close to the Aegean Sea populations than they are to the Black Sea populations in both cases. Populations from the Atlantic side of the Strait of Gibraltar are differentiated from those on the Mediterranean side in both species, a pattern that confirms the results of the wide scale study. Along the dunes of West France no clear genetic structure could be detected in any of the species. Additionally, the results from the Baltic Sea/North Sea populations of C. maritima did not reveal any geographical genetic pattern. It is postulated that the many congruencies between the species are mainly due to a predominantly sea water mediated seed dispersal in both species and their shared sandy habitat. The results are compared to hypothetical distributions for the last glacial maximum based on species specific temperature requirements. It is argued that in both species the geographical borders of the clusters in the Mediterranean area were not affected by quaternary temperature changes and that the Aegean/Black Sea/Marmara cluster, and possibly the Ionian Sea/Adriatic Sea cluster in C. maritima, is the result of sea currents that isolate these basins from the rest of the sampled areas. The genetic gap in the Strait of Gibraltar between Atlantic Ocean and Mediterranean Sea populations in both species is also explained in terms of sea currents. The existence of three subgroups corresponding to the Aegean Sea, Black Sea and Sea of Marmara basins is suggested to have arisen due to geographical isolation during periods of global sea regressions in the glacials. The population genetic evidence was inconclusive regarding the Baltic Sea cluster of C. Maritima from the wide scale study. The results of this study are very similar to those of an investigation of three other coastal plant species over a similar range. This suggests that the phylo-geographic patterns of widespread coastal plants may be more predictable than those of other terrestrial plants.

Palaeo wind system reconstruction of the last glacial period over Europe, using high resolution proxy data and model-data-comparison

The atmosphere is a global influence on the movement of heat and humidity between the continents, and thus significantly affects climate variability. Information about atmospheric circulation are of major importance for the understanding of different climatic conditions. Dust deposits from maar lakes and dry maars from the Eifel Volcanic Field (Germany) are therefore used as proxy data for the reconstruction of past aeolian dynamics.rnrnIn this thesis past two sediment cores from the Eifel region are examined: the core SM3 from Lake Schalkenmehren and the core DE3 from the Dehner dry maar. Both cores contain the tephra of the Laacher See eruption, which is dated to 12,900 before present. Taken together the cores cover the last 60,000 years: SM3 the Holocene and DE3 the marine isotope stages MIS-3 and MIS-2, respectively. The frequencies of glacial dust storm events and their paleo wind direction are detected by high resolution grain size and provenance analysis of the lake sediments. Therefore two different methods are applied: geochemical measurements of the sediment using µXRF-scanning and the particle analysis method RADIUS (rapid particle analysis of digital images by ultra-high-resolution scanning of thin sections).rnIt is shown that single dust layers in the lake sediment are characterized by an increased content of aeolian transported carbonate particles. The limestone-bearing Eifel-North-South zone is the most likely source for the carbonate rich aeolian dust in the lake sediments of the Dehner dry maar. The dry maar is located on the western side of the Eifel-North-South zone. Thus, carbonate rich aeolian sediment is most likely to be transported towards the Dehner dry maar within easterly winds. A methodology is developed which limits the detection to the aeolian transported carbonate particles in the sediment, the RADIUS-carbonate module.rnrnIn summary, during the marine isotope stage MIS-3 the storm frequency and the east wind frequency are both increased in comparison to MIS-2. These results leads to the suggestion that atmospheric circulation was affected by more turbulent conditions during MIS-3 in comparison to the more stable atmospheric circulation during the full glacial conditions of MIS-2.rnThe results of the investigations of the dust records are finally evaluated in relation a study of atmospheric general circulation models for a comprehensive interpretation. Here, AGCM experiments (ECHAM3 and ECHAM4) with different prescribed SST patterns are used to develop a synoptic interpretation of long-persisting east wind conditions and of east wind storm events, which are suggested to lead to an enhanced accumulation of sediment being transported by easterly winds to the proxy site of the Dehner dry maar.rnrnThe basic observations made on the proxy record are also illustrated in the 10 m-wind vectors in the different model experiments under glacial conditions with different prescribed sea surface temperature patterns. Furthermore, the analysis of long-persisting east wind conditions in the AGCM data shows a stronger seasonality under glacial conditions: all the different experiments are characterized by an increase of the relative importance of the LEWIC during spring and summer. The different glacial experiments consistently show a shift from a long-lasting high over the Baltic Sea towards the NW, directly above the Scandinavian Ice Sheet, together with contemporary enhanced westerly circulation over the North Atlantic.rnrnThis thesis is a comprehensive analysis of atmospheric circulation patterns during the last glacial period. It has been possible to reconstruct important elements of the glacial paleo climate in Central Europe. While the proxy data from sediment cores lead to a binary signal of the wind direction changes (east versus west wind), a synoptic interpretation using atmospheric circulation models is successful. This shows a possible distribution of high and low pressure areas and thus the direction and strength of wind fields which have the capacity to transport dust. In conclusion, the combination of numerical models, to enhance understanding of processes in the climate system, with proxy data from the environmental record is the key to a comprehensive approach to paleo climatic reconstruction.rn

Flugzeuggetragene in-situ Messungen zur Eis- und Flüssigphase troposphärischer Wolken

Die Mikrophysik in Wolken bestimmt deren Strahlungseigenschaften und beeinflusst somit auch den Strahlungshaushalt des Planeten Erde. Aus diesem Grund werden im Rahmen der vorliegenden Arbeit die mikrophysikalischen Charakteristika von Cirrus-Wolken sowie von arktischen Grenzschicht-Wolken behandelt. Die Untersuchung dieser Wolken wurde mithilfe verschiedener Instrumente verwirklicht, welche Partikel in einem Durchmesserbereich von 250nm bis zu 6.4mm vermessen und an Forschungsflugzeugen montiert werden. Ein Instrumentenvergleich bestätigt, dass innerhalb der Bereiche in denen sich die Messungen dieser Instrumente überlappen, die auftretenden Diskrepanzen als sehr gering einzustufen sind. Das vorrangig verwendete Instrument trägt die Bezeichnung CCP (Cloud Combination Probe) und ist eine Kombination aus einem Instrument, das Wolkenpartikel anhand von vorwärts-gerichtetem Streulicht detektiert und einem weiteren, das zweidimensionale Schattenbilder einzelner Wolkenpartikel aufzeichnet. Die Untersuchung von Cirrus-Wolken erfolgt mittels Daten der AIRTOSS-ICE (AIRcraft TOwed Sensor Shuttle - Inhomogeneous Cirrus Experiment) Kampagne, welche im Jahr 2013 über der deutschen Nord- und Ostsee stattfand. Parameter wie Partikeldurchmesser, Partikelanzahlkonzentration, Partikelform, Eiswassergehalt, Wolkenhöhe und Wolkendicke der detektierten Cirrus-Wolken werden bestimmt und im Kontext des aktuellen Wissenstandes diskutiert. Des Weiteren wird eine beprobte Cirrus-Wolke im Detail analysiert, welche den typischen Entwicklungsprozess und die vertikale Struktur dieser Wolkengattung widerspiegelt. Arktische Grenzschicht-Wolken werden anhand von Daten untersucht, die während der VERDI (VERtical Distribution of Ice in Arctic Clouds) Kampagne im Jahr 2012 über der kanadischen Beaufortsee aufgezeichnet wurden. Diese Messkampagne fand im Frühling statt, um die Entwicklung von Eis-Wolken über Mischphasen-Wolken bis hin zu Flüssigwasser-Wolken zu beobachten. Unter bestimmten atmosphärischen Bedingungen tritt innerhalb von Mischphasen-Wolken der sogenannte Wegener-Bergeron-Findeisen Prozess auf, bei dem Flüssigwassertropfen zugunsten von Eispartikeln verdampfen. Es wird bestätigt, dass dieser Prozess anhand von mikrophysikalischen Messungen, insbesondere den daraus resultierenden Größenverteilungen, nachweisbar ist. Darüber hinaus wird eine arktische Flüssigwasser-Wolke im Detail untersucht, welche im Inneren das Auftreten von monomodalen Tröpfchen-Größenverteilungen zeigt. Mit zunehmender Höhe wachsen die Tropfen an und die Maxima der Größenverteilungen verschieben sich hin zu größeren Durchmessern. Dahingegen findet im oberen Übergangsbereich dieser Flüssigwasser-Wolke, zwischen Wolke und freier Atmosphäre, ein Wechsel von monomodalen zu bimodalen Tröpfchen-Größenverteilungen statt. Diese weisen eine Mode 1 mit einem Tropfendurchmesser von 20μm und eine Mode 2 mit einem Tropfendurchmesser von 10μm auf. Das dieses Phänomen eventuell typisch für arktische Flüssigwasser-Wolken ist, zeigen an dem Datensatz durchgeführte Analysen. Mögliche Entstehungsprozesse der zweiten Mode können durch Kondensation von Wasserdampf auf eingetragenen Aerosolpartikeln, die aus einer Luftschicht oberhalb der Wolke stammen oder durch Wirbel, welche trockene Luftmassen in die Wolke induzieren und Verdampfungsprozesse von Wolkentröpfchen hervorrufen, erklärt werden. Unter Verwendung einer direkten numerischen Simulation wird gezeigt, dass die Einmischung von trockenen Luftmassen in den Übergangsbereich der Wolke am wahrscheinlichsten die Ausbildung von Mode 2 verursacht.