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Impact of matric potential and pore size distribution on growth dynamics of filamentous and non-filamentous soil bacteria
No full textThe filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities.
Year-round itinerary of a GPS-tracked Brent Goose Branta b. bernicla that visited the Bassin d’Arcachon
No full textThe year-round itinerary for a Dark-bellied Brent Goose Branta b. bernicla is described for a bird fitted with a GPS tracking device at Terschelling Island, the Netherlands, in spring 2012. Spring migration commenced when the bird left the Dutch Wadden Sea on 27 May and continued until it reached the Taimyr Peninsula in arctic Russia on 8 June. During the summer months it moved along the coast of the Taimyr Peninsula, prior to moulting on Taimyr Island to the north of the peninsula in July. During autumn migration it frequented eelgrass Zostera sp. beds around Langeness Island in Schleswig-Holstein, Germany and then proceeded to the Bassin d’Arcachon in France, another famous eelgrass area, where it remained from 18 October 2012–12 January 2013 before returning to feed on grassland polders on Terschelling Island in January 2013. The timing of the location data showed that the bird flew large distances in short periods of time during migration. Over the year it covered c. 4,600 km during local movements and c. 15,000 km on migration. The results form part of a larger study investigating the importance of non-breeding habitats (particularly eelgrass vegetation) for the species.
Publieke schuld in de vroegmoderne Nederlanden: een financiële revolutie?
No full textAflsluitende lezing op uitnodiging, tevens de eerdere lezingen samenvattend, over vroegmoderne schuld in de Nederlanden. De focus is op het gebuik van de term 'financiele revolutie', destijds geintroduceerd door James Tracy. Spreker toont aan dat deze term nog steeds van belang is gezien de fundamentele innovaties in de openbare financien in de zestiende- en zeventiende eeuwse Nederlanden en het gemak waarmee men oorlogen kon financieren.
