Ein Verfahren zur Bestimmung der Lagerungsdichte skelettreicher oder geringmächtiger Bodenhorizonte

A method for bulk density determination of gravel rich or thin soil horizons A limitation of bulk density determinations using the core sample method is that soil horizons must be thick enough for coring and nearly free of rock material. The significance of the proposed method lies in the fact that it is applicable also to soil samples rich in rock fragments and/or thin horizons. The samples are impregnated in the laboratory using an epoxy resin. Bulk density (ρ_b) is determined after hardening according to the following equation: ρ_f = density of soil material Bulk densities determined by the new method were found to agree well with such resulting from the core sample method.     

Über die Aggregatdichte und deren mögliche Auswirkung auf den Bodenlösungstransport

On the bulk density of aggregates and its possible impact on the movement of soil solutions The bulk densities of the aggregate fractions 15-18 mm, 10-15 mm, 5-10 mm, and 3-5 mm from a Typic Hapludalf, an Aquic Hapludalf, and a Typic Chromudert, all used as cropland and grassland, and that of aggregates of the 3-5 mm fraction from a Typic Dystrochrept used for a farm manure and crop residue trial, lay between 1.8 and 2.0 g/cm³. Sampling was done down to depths of 85 cm, 70 cm, 55 cm, and 80 cm. respectively. The bulk density values increase in most cases with decreasing aggregate size and indicate the aggregate pore volumes to generally range from 25 to 35% b.v. This means that either soil aggregates often contain only fine pores or that fine and medium pores also act as inter-aggregate pores. As a consequence, movement and exchange of soil water and soil solution between inter- and intra-aggregate pores is severely restricted.     

Die Bedeutung der Festigkeitsverteilung in Einzelaggregaten für den Wasser- und Stofftransport im Boden

Relevance of strength distribution within aggregates to the movement of soil water and soil solution Different transport processes exist not only between the total soil and single aggregates, but also within individual aggregates. To clarify the structure of single aggregates without thin-sectioning, resistance to penetration was repeatedly measured on the same aggregate at a predefined soil water tension. The aggregates were sampled from the G_{o 2} horizon of a Typic Fluvaquent (Φ 15-25mm) and from the B_{g 2} horizon of an Aquic Chromudert (Φ 30-50mm) and equilibrated with water tensions ranging from roughly OhPa to 1000hPa. The strength distributions within individual aggregates were calculated using penetration resistance values of all measurements on one aggregate at a single water tension. These distributions, as exemplified by those at 300hPa and 1000hPa. show that the aggregates are surrounded by a thin, but very strong mineral skin which may be discontinuous, especially for aggregates from the Aquic Chromudert soil. In these aggregates, slickenside-like friction planes were found to penetrate through the skin. The deviation in the skin composition from that of the inner-aggregate described in literature, together with the finding of its strength, suggest that the exchange of water and solutes between the inter-aggregate and intra-aggregate pores is strongly impeded. The weaker parts within the skin, however, must be interpreted as preferred pathways, perhaps resulting in some fingering within aggregates at the prevailing matrix potential. The significance of different pathways within aggregates for the general transport of matter in soils is briefly discussed.     

Der Einfluß einer Kalkung auf Aggregatstabilität und Eindringwiderstand zweier Lößböden

Aggregate Stability and Penetration Resistance of two Normal and Limed Soils To investigate the meliorative effect of liming, the aggregate stability (determined by wet sieving and sedimentation) and the penetration resistance (by a previously described method (Becher 1973 a) of unlimed and limed samples of two field experiments on a Brown Earth-Pseudogley and a Humic Pseudogley were determined. Penetration resistance decreased with decreasing water suction, but it did not show significant relation to liming. Aggregate stability was increased by liming on the Brown Earth-Pseudogley but was lowered on the Humic Pseudogley, while penetration resistance was only influenced in some cases. The behaviour of the Humic Pseudogley was explained by its exceptional high organic matter content (5–6%).     

Pestivirus and alphaherpesvirus infections in Swedish reindeer (Rangifer tarandus tarandus L.)

Herding semi-domesticated reindeer has economic and social value for Sami people in the northern territories of Fennoscandia. However, with the intensification of reindeer husbandry, interspecies transmission of pathogens between reindeer and domestic animals may become a problem, especially for countries such as Sweden, Norway, and Finland where pestivirus and alphaherpesvirus have been eradicated in domestic ruminants. This study, which included 1158 Swedish reindeer, showed relatively high prevalence of antibodies against bovine viral diarrhoea virus (BVDV) (32%) and bovine herpesvirus-1 (BoHV-1) (53%). Adult animals were more often seropositive for BVDV and BoHV-1 (50% and 78%, respectively) than were calves (18 and 11%, respectively). While the seroprevalence of alphaherpesvirus was similar in different herding districts, pestivirus seropositivity was highest in the South and diminished towards the North of the Swedish reindeer herding area. High correlation of the seropositivity against both pathogens at both individual and herd levels may indicate possible mutual synergetic effects and may be explained by the immunosuppressive nature of the viruses. While alphaherpesvirus seroprevalence was probably related to putative cervid herpesvirus 2 (CvHV-2), the pestivirus infecting reindeer remains undefined. The virus neutralisation test of reindeer sera using different pestivirus strains, revealed higher titres against Border disease virus strains like 137/4 (BDV-1) and Reindeer-1 (BDV-2) than against BVDV-1. However, the virus was not identified by real time RT-PCR in any of the samples (n=276) from seronegative reindeers. The study showed that pestivirus and alphaherpesvirus infections are endemic in the Swedish reindeer population.     

Substrate-controlled succession of marine bacterioplankton populations induced by a phytoplankton bloom

Phytoplankton blooms characterize temperate ocean margin zones in spring. We investigated the bacterioplankton response to a diatom bloom in the North Sea and observed a dynamic succession of populations at genus-level resolution. Taxonomically distinct expressions of carbohydrate-active enzymes (transporters; in particular, TonB-dependent transporters) and phosphate acquisition strategies were found, indicating that distinct populations of Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria are specialized for successive decomposition of algal-derived organic matter. Our results suggest that algal substrate availability provided a series of ecological niches in which specialized populations could bloom. This reveals how planktonic species, despite their seemingly homogeneous habitat, can evade extinction by direct competition.     

Heterogeneity of ruminant pestiviruses: academic interest or important basis for the development of vaccines and diagnostics?

Pestiviruses cause economically important diseases of farm animals. Members of the Pestiviruses are bovine viral diarrhea virus 1 (BVDV-1), BVDV-2, classical swine fever virus (CSFV) and border disease virus (BDV). Phylogenetic analyses based on the entire nucleic acid sequence encoding the Npro allow a statistically significant segregation of established species and of subgroups within the species. BVDV-1 strains isolated in Germany can be associated with at least five different subgroups. In contrast all BVDV-2 isolates detected in Germany so far are closely related, belonging to one subgroup. A group of virus isolates from sheep and zoo animals is clearly different from established pestivirus species and can be designated as BDV-2. Antigenetic relatedness of pestiviruses was studied using defined virus isolates and antisera in cross-neutralization assays. Six antigenic groups were distinguished corresponding to the genetic clusters BVDV-1, BVDV-2, CSFV, BDV-1, BDV-2 and Giraffe-1. A significant antigenic difference was also observed between members of subgroups 1a and 1b of BVDV-1. Studies on the genetic and antigenic heterogeneity of pestiviruses are important for the development of new vaccines, diagnostic tests and for eradication programs.