Climatic significance of glacier retreat and rockglaciers re-assessed in the light of cosmogenic dating and weathering rind thickness in Clarée valley (Briançonnais,French Alps)

Recent advances in geochronology provide opportunities to identify the glacial and periglacial sequences in mountain area. In this paper, we focus on the Upper Durance catchment (Southern French Alps), in the Clarée valley, where no absolute chronological benchmark was defined. Glacial remnants and periglacial features were investigated, integrated within a chronological scenario thanks to relative (weathering rind thickness) and absolute (CRE technique) dates. We find evidence of the existence of a Late-Glacial valley glacier, that has never been reported before. Then the upper valleys became ice-free during a period corresponding to the Early-Holocene Climate Optimum, whereas two sequences of cirque glaciation are identified during the second half of the Holocene. We also show evidence of three main generations of rockglaciers, which also mainly developed during the second half of the Holocene, probably at the end of the Subboreal period. The location and the altitudes of rockglaciers are strongly dependent on the geomorphic setting (especially the location of the sediment sources), hence complicating their palaeo-climatic interpretations.     

Conservation of species interaction networks

Recent work has shown that antagonist (e.g. predator-prey food web) and mutualist (e.g. pollinator-plant) network structure can be altered by global environmental change drivers, and that these alterations may have important ecosystem-level consequences. This has prompted calls for the conservation of network structure, but precisely which attributes of webs should be conserved remains unclear. Further, the extent to which network metrics characterise the spatiotemporally-variable dynamic structure of interacting communities is unknown. Here, we summarise the attributes of web structure that are predicted to confer stability or increased function to a system, as these may be of greatest interest to conservation biologists. However, empirical evaluation of these effects is lacking in most cases, and we discuss whether stability is even desirable in all contexts. The incorporation of web attributes into conservation monitoring requires that changes in these attributes can be recorded (sampled) with relative ease. We contrast the sensitivity of metrics to sampling effort, and highlight those (such as nestedness and connectance) that could easily be incorporated into conservation monitoring. Despite our growing understanding of the characteristics of food webs that confer stability and function, numerous practical challenges need to be overcome before the goal of conserving species interaction networks can be achieved.     

The functional structure of ectomycorrhizal communities in an oak forest in central France witnesses ancient Gallo-Roman farming practices

The activities of nutrient-mobilising enzymes secreted by ectomycorrhizas of sessile oak (Quercus petraea) have been measured in 24 plots in a forested area in central France where many rural Gallo-Roman settlements (first to fifth centuries AD) have been discovered. Data have been related with tree growth and soil chemical properties. Although soil near the past settlements is still enriched in N and P, this does not always correspond to the higher productivity of oak trees. However, when this is the case, the ectomycorrhizal community displays higher chitinase, protease and phosphatase activities (involved in N and P mobilisation from soil organic matter). A few specialised ectomycorrhizal fungal species are responsible for this adaptation to the long-lasting modification of soil conditions.     

An association exists between bovine herpesvirus-4 seropositivity and abortion in cows

The prevalence of cattle seropositive to bovine herpesvirus-4 (BHV-4) is high in Belgium. In Belgian farms, clinical signs associated with BHV-4 infection essentially involve the genital tract and consist mainly of postpartum metritis or metroperitonitis. The role of BHV-4 in abortion has not been definitively demonstrated but epidemiological and experimental facts suggest its involvement. A seroepidemiological investigation was therefore conducted as a case-control study to compare the seroprevalences of BHV-4 infections in the aborted-cow population and in a randomly selected control group in the province of Liège (Belgium). The seroprevalence (17.2%) in aborted cows was significantly higher than that of the control group (10.0%). The odds ratio (OR) was 1.87 (1.06 < 3.30). BHV-4 infection is therefore considered as a risk factor for abortion in cows.     

Associations between dairy herd management factors and bulk tank milk antibody levels against Ostertagia ostertagi

A cross-sectional questionnaire survey was performed on dairy herds in Flanders (Belgium) to detect management factors that are associated with an increased gastrointestinal parasite infection level of adult dairy cows. At the end of the grazing season, information concerning general herd factors, pasture management and anthelmintic treatment strategy was obtained from 956 herds. A bulk tank milk sample was obtained from 779 out of the 956 herds and the antibody levels (ODR) against Ostertagia ostertagi were determined. The associations between ODR and herd management factors were studied by two linear regression models. The first model evaluated the effect of general herd factors and the level of the cows' exposure to pasture. Large sized herds had significantly lower ODRs as compared to medium (P=0.001) or small sized herds (P=0.03). Herds with only dairy cows had lower ODRs than herds with both dairy and beef cows (P=0.02). An increased exposure to pasture of the cows was associated with higher ODRs (P<0.001). The second model was built to evaluate the effect of pasture management factors and anthelmintic treatment strategy. Later turn-out on pasture (P<0.001) and mowing (P=0.002) were both significantly associated with lower ODRs. Cows that had a restricted grazing time per day tended to have lower ODR than cows that grazed 24 h per day (P=0.07). An increased exposure to pasture of the heifers was significantly associated with higher ODRs (P=0.001). No associations were found between ODR and calf related management factors, anthelmintic treatment strategy, time of turn-in, rotational grazing type or stocking rate. Later turn-out on pasture, mowing and restricting the grazing time per day are factors that can be applied immediately on dairy farms to reduce economical losses due to gastrointestinal nematodes.     

Quadricuspid aortic valve and associated abnormalities in a dog

An 11-month-old, female Scottish terrier was presented with a history of a heart murmur. The electrocardiogram showed signs of left ventricular enlargement, and radiography confirmed generalized cardiomegaly. Echocardiography revealed four equally sized aortic valve cusps. A ventricular septal defect, with systolic left-to-right shunting, and aortic regurgitation into both ventricles were also present. The dog was free of clinical signs 1 year after diagnosis.     

Prevalence and identity of cdt-related sequences in necrotoxigenic Escherichia coli

The cytolethal distending toxins (CDT) are responsible for the mitosis block at G2/M and the cycle arrest of cells in culture. Escherichia coli isolated from humans and animals with intestinal and extra-intestinal diseases can be positive for the production of a CDT-like cytopathic effect or for the presence of cdt-related genes. The purpose of this study was to compare the prevalence and the identity of cdt-related sequences in necrotoxigenic E. coli (NTEC). A collection of 98 bovine type 2 NTEC (NTEC2) and 45 bovine, 20 canine, 3 feline, 65 human and 129 porcine type 1 NTEC (NTEC1) isolates was studied by colony hybridisation and PCR assays specific for the cdtB genes encoding the B sub-unit of the CDT-I, CDT-II, CDT-III and CDT-IV toxins produced by E. coli. cdtB-III sequences were frequent amongst bovine NTEC2, since 83% of these isolates were positive by colony hybridisation and/or PCR, whereas cdtB-related sequences were rare amongst NTEC1, since only 2 bovine (4%), 3 canine (15%), 10 human (15%) and 13 porcine (10%) of these isolates were positive. The 28 probe-positive NTEC1 harboured cdtB-IV sequences (13 isolates), cdtB-I sequences (10 isolates), or still unidentified cdt-related sequences (5 isolates). After comparison with previously published and unpublished results of phenotypic assay on cell cultures, existence of other cdt-related sequences is suggested amongst NTEC1. The differences between NTEC1 and NTEC2 in their CDT profiles may have implication for the pathogenesis of those two classes of pathogenic E. coli.