Treeline Fluctuations Recorded for 12,500 Years by Soil Profiles, Pollen, and Plant Macrofossils in the Central Swiss Alps

Past treelines can rarely be recorded by pollen percentages alone, but pollen concentration, pollen influx, and plant macrofossils (including stomata of conifers) are more reliable indicators. In addition, ancient forest soils above today's treeline may trace the maximum upper expansion of the forest since the last glaciation. Charcoal in such soil profiles may be radiocarbon dated. Our example from the Central Swiss Alps at the Alpe d'Essertse consists of a plant-macrofossil diagram and pollen diagrams of the pond Gouille Rion at 2343 m a.s.l. and a sequence of soil profiles from 1780 m to 2600 m a.s.l. The area around the pond was forested with LariJc decidua and Pinus cembra between 9500 and 3600 BP. After 4700 BP the forest became more open and Juniperus nana and Alnus viridis expanded (together with Picea abies in the subalpine forest). Between 1700 and 900 BP the Juniperus nana and Alnus viridis scrubs declined while meadows and pastures took over, so that the pond Gouille Rion was definitively above timber­ line. The highest Holocene treeline was at 2400 to 2450 m a.s.l. (i.e. 50 to 100 m higher than the uppermost single specimen of Pinus cembra today) between 9000 and 4700 BP, but it is not yet dated in more detail. The highest charcoal of Pinus cembra at 2380 m a.s.l. has a radiocarbon date of 6010 ± 70 BP. Around 6900 BP a strong climatic deterioration caused an opening of timberline forest. First indicators of anthropogenic influence occurred at 4700 BP, when the forest limit started to move down. The lowering of timberline after 4700 BP was probably due to combined effects of human and climatic impact.

Quartärbotanische Untersuchungen zur Vegetationsgeschichte der Alpe d'Essertse (Hérémence, Wallis)

Afin d'étudier l'histoire de la végétation de l'Alpe d'Essertse, des sondages ont été effectués dans le Gouillé Rion, un étang situé à 2343 m d'altitude. Les grains de pollen contenus dans le sédiment lacustre ont été analysés palynologiquement. Le diagramme pollinique montre qu'après le retrait des glaciers vers 13000 BP (Before Present), l'Alpe d'Essertse fut colonisée par une végétation alpine et une végétation d'éboulis. Entre 9500 et 3600 BP le mélèze (Larix decidua) et l'arole (Pinus cembra) formaient une forêt qui atteignait au moins 2343 m. A partir de 5000 BP la forêt s'ouvrit et la limite de la forêt commença à s'abaisser. Des buissons d'aune vert (Alnus viridis) remplacèrent peut à peu la forêt. Entre 1700 et 900 BP seulement, cette végétation apparentée aux forêts fit place aux prés et pâturages. Seul l'utilisation d'autres méthodes permet d'estimer la limite d'altitude maximale atteinte par la forêt au cours de l'holocène: pour l'Alpe d'Essertse des charbons trouvés dans le sol, ainsi que des bioséquences pédologiques suggèrent une limite de la forêt maximale entre 2400 et 2450 m d'altitude.

Reconstruction of Holocene vegetation dynamics at Lac de Bretaye, a high-mountain lake in the Swiss Alps

A deeper understanding of past vegetation dynamics is required to better assess future vegetation responses to global warming in the Alps. Lake sediments from Lac de Bretaye, a small subalpine lake in the Northern Swiss Alps (1780 m a.s.l.), were analysed to reconstruct past vegetation dynamics for the entire Holocene, using pollen, macrofossil and charcoal analyses as main proxies. The results show that timberline reached the lake’s catchment area at around 10,300 cal. BP, supporting the hypothesis of a delayed postglacial afforestation in the Northern Alps. At the same time, thermophilous trees such as Ulmus, Tilia and Acer established in the lowlands and expanded to the altitude of the lake, forming distinctive boreo-nemoral forests with Betula, Pinus cembra and Larix decidua. From about 5000 to 3500 cal. BP, thermophilous trees declined because of increasing human land use, mainly driven by the mass expansion of Picea abies and severe anthropogenic fire activity. From the Bronze Age onwards (c. 4200–2800 cal. BP), grazing indicators and high values for charcoal concentration and influx attest an intensifying human impact, fostering the expansion of Alnus viridis and Picea abies. Hence, biodiversity in alpine meadows increased, whereas forest diversity declined, as can be seen in other regional records. We argue that the anticipated climate change and decreasing human impact in the Alps today will not only lead to an upward movement of timberline with consequent loss of area for grasslands, but also to a disruption of Picea abies forests, which may allow the re-expansion of thermophilous tree species.

Benthic fauna at station FINO 1, 2005-2007

In der Nordsee wurden auf der Forschungsplattform FINO 1 Felduntersuchungen durchgeführt, um spezielle Fragen zu möglichen Auswirkungen von Offshore-Windenergieparks auf die marine Umwelt zu beantworten. Der Fokus war dabei auf die Konsequenzen für die Lebensgemeinschaft am Meeresboden gerichtet. Es wurden die benthosökologischen Prozesse im Nahbereich der Piles sowie die mittelfristige Entwicklung der Aufwuchsfauna auf der künstlichen Unterwasserstruktur dokumentiert. Die Ansammlung pelagischer Fischen um die Plattform und der Export organischen Materials von der Plattform wurden quantifiziert. Die räumliche Ausdehnung und die Erheblichkeit von Auswirkungen auf die Lebensgemeinschaften des Meeresbodens wurden anhand mathematischer Modellierung abgeschätzt. Zusätzlich wurde die Anwendbarkeit der elektrochemischen Akretionstechnologie zur Schaffung naturnaher Kalksubstrate in der Nordsee getestet und geeignete Parameter für eine erfolgreiche Umsetzung unter Nordseebedingungen ermittelt. Die auch 4,5 Jahre nach Errichtung der Plattform noch ansteigende Artenzahl der Aufwuchsfauna lässt darauf schließen, dass der Sukzessionsprozess noch nicht abgeschlossen ist. Die stark vertikal zonierte Aufwuchsfauna auf der Unterwasserkonstruktion erreicht eine Masse von ca. 5 Tonnen mit ausgeprägten saisonalen Schwankungen. Anhand von echoakustischen Untersuchungen wurden saisonal auftretende Ansammlungen pelagischer Fische um die Plattform dokumentiert. Der Nahbereich der Plattform unterschied sich durch eine Schillauflage und eine räumlich und zeitlich sehr variable Sediment- und Bodenfaunazusammensetzung deutlich von einem Referenzgebiet in 200-400 m Abstand von der Plattform. Eine konzentrische Zonierung mit unterschiedlich stark ausgeprägten Veränderungen der Bodenfauna lässt auf komplexe Veränderung des gesamten lokalen Nahrungsgefüges im Nahbereich der Plattform schließen. Anhand einer Modellierung konnte der Materialexport in die umgebenden Weichbodenbereiche für einzelne Piles und einen hypothetischen Windpark abgeschätzt werden. Die lokale Ausbildung einer hohen Biomasse auf der Unterwasserkonstruktion von WEA sowie der Export mit anschließender Sedimentation lassen zumindest lokal einen erheblichen Einfluss auf Stoff- und Energieflüsse erwarten.

Microbiota and Microsatellite genotypes of Pacific oysters stemming from three oyster bed in the Northern Wadden Sea

Background: Studies of oyster microbiomes have revealed that a limited number of microbes, including pathogens, can dominate microbial communities in host tissues such as gills and gut. Much of the bacterial diversity however remains underexplored and unexplained, although environmental conditions and host genetics have been implicated. We used 454 next generation 16S rRNA amplicon sequencing of individually tagged PCR reactions to explore the diversity of bacterial communities in gill tissue of the invasive Pacific oyster Crassostrea gigas stemming from genetically differentiated beds under ambient outdoor conditions and after a multifaceted disturbance treatment imposing stress on the host. Results: While the gill associated microbial communities in oysters were dominated by few abundant taxa (i.e. Sphingomonas, Mycoplasma) the distribution of rare bacterial groups correlated to relatedness between the hosts under ambient conditions. Exposing the host to disturbance broke apart this relationship by removing rare phylotypes thereby reducing overall microbial diversity. Shifts in the microbiome composition in response to stress did not result in a net increase in genera known to contain potentially pathogenic strains. Conclusion: The decrease in microbial diversity and the disassociation between population genetic structure of the hosts and their associated microbiome suggest that disturbance (i.e. stress) may play a significant role for the assembly of the natural microbiome. Such community shifts may in turn also feed back on the course of disease and the occurrence of mass mortality events in oyster populations.

Results of magnetic analysis

Microorganisms are a primary control on the redox-induced cycling of iron in the environment. Despite the ability of bacteria to grow using both Fe(II) and Fe(III) bound in solid-phase iron minerals, it is currently unknown if changing environmental conditions enable the sharing of electrons in mixed-valent iron oxides between bacteria with different metabolisms. We show through magnetic and spectroscopic measurements that the phototrophic Fe(II)-oxidizing bacterium Rhodopseudomonas palustris TIE-1 oxidizes magnetite (Fe3O4) nanoparticles using light energy. This process is reversible in co-cultures by the anaerobic Fe(III)-reducing bacterium Geobacter sulfurreducens. These results demonstrate that Fe ions bound in the highly crystalline mineral magnetite are bioavailable as electron sinks and electron sources under varying environmental conditions, effectively rendering a naturally occurring battery.

Palynology on a profile from the Krusné Hory Mountains

Site details: The raised bog Fláje-Kiefern (50°429N, 13°329 E; 760 m a.s.l.; size ca. 500x500 m) lies in the Krusné Hory Mountains (Erzgebirge), Czech Republic, about 10 km from Georgenfelder Moor in Germany. Hejny and Slavík (1988) described the phytogeographic region of the Krusne Hory Mountains as 'a region of mountain flora and vegetation, with thermophilous species largely missing. In the natural forests, conifers, especially spruce (Picea excelsa) prevail. The deforested areas have been converted into meadows and pastures'. The climate is cool with annual average temperatures of about 5°C and annual precipitation of about 900 mm. The bedrock is Precambrian crystallinicum.

Pollen and macrofossils profiles and age determination from three cores in Northeastern Kansas, U.S.A.

Two marshes near Muscotah and Arrington, Atchison County, northeastern Kansas, yielded a pollen sequence covering the last 25,000 yrs of vegetation development. The earliest pollen spectra are comparable with surface pollen spectra from southern Saskatchewan and southeastern Manitoba and might indicate a rather open vegetation but with some pine, spruce, and birch as the most important tree species, with local stands of alder and willow. This type of vegetation changed about 23,000 yrs ago to a spruce forest, which prevailed in the region until at least 15,000 yrs ago. Because of a hiatus, the vegetation changes resulting in the spread of a mixed deciduous forest and prairie, which was present in the region from 11,000 to 9,000 yrs ago, remain unknown. Prairie vegetation, with perhaps a few trees along the valleys, covered the region until about 5,000 yrs ago, when a re-expansion of deciduous trees began in the lowlands.