Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2013
Abstract
This study combines tree-ring and charcoal data to explore possible drivers of the charcoal record and its spatial variation in a boreal Norwegian forest landscape. Peat and mineral soil samples were collected in a multiple site sampling approach and the amount of charcoal in the peat is related to fire history, Holocene climate variation, major shifts in the vegetation composition, and fuel availability. Dendrochronologic dating was used to reveal the fire history over the last 600 years with spatial and temporal accuracy, and AMS radiocarbon dating of 20 peat columns and their charcoal records from four peatlands was used to elucidate the fire history over the Holocene. The average amount of charcoal was about 2.5 times higher in the mineral soil than in the peat (270 versus 100 g/m², respectively), and there were considerable between- and within-site variations. There was no relationship between the age of a given peatland and its content of charcoal, nor between the amount of charcoal in a given peatland and in the neighboring mineral soil. Although most of the charcoal mass in the peatlands was found in parts of the peat columns originating from relatively warm climatic periods and from the period before the local establishment of Norway spruce (Picea abies), charcoal accumulation rates (per 1000 yr) were higher during cold climatic periods and similar before and after spruce establishment. Recent fires showed up to a low degree in the peat columns. On fine spatial scales (1–10 m), fuel quality and distribution together with fire behaviour throughout millennia are likely to be responsible for variations in the charcoal record. On the landscape scale (100–1000 m), the charcoal records were site-specifically idiosyncratic, presumably due to topography, distribution of fire breaks and fuel types, and human land use, coupled with long-term variations inherent in these factors.
Abstract
Shoot dieback disease of European ash caused by the ascomycete Hymenoscyphus pseudoalbidus threatens ash on a continental scale. A spore sampler placed in a diseased ash forest in Southern Norway, coupled with microscopy and DNA-based fungal species-specific real-time PCR assays, was employed to profile diurnal and within-season variation in infection pressure by ascospores of H. pseudoalbidus and the potentially co-existing non-pathogenic Hymenoscyphusalbidus. Hymenoscyphus pseudoalbidus was found to be predominant in the stand. Massive simultaneous liberation, by active discharge of pathogen ascospores in the morning, peaked in mid-Jul. to mid-Aug. Accumulation of pathogen DNA on leaflets of current-year leaves reached a high level plateau phase before appearance of autumn coloration, suggesting that pathogen establishment in leaves is terminated before the onset of leaf senescence.
Authors
Ingebjørg Helena Nymo Jacques Godfroid Kjetil Åsbakk Anett Kristin Larsen Carlos G Das Neves Rolf Rødven Morten TrylandAbstract
No abstract has been registered
Abstract
The quality of surface water and groundwater is closely related to flow paths in the vadose zone. Therefore, dye tracer studies are often carried out to visualise flow patterns in soils. These experiments provide images of stained soil profiles and their evaluation demands knowledge in hydrology as well as in image analysis and statistics. The classical analysis consists of image classification in stained and non-stained parts and calculation of the dye coverage (i.e. the proportion of staining). The variation of this quantity with depth is interpreted to identify dominant flow types. While some feature extraction from images of dye-stained profiles is necessary, restricting the analysis to the dye coverage alone might miss important information. In our study we propose to use several index functions to extract different (ideally complementary) features. We associate each image row with a feature vector (i.e. a certain number of image function values) and use these features to cluster the image rows to identify similar image areas. Because images of stained profiles might have different reasonable clusterings, we calculate multiple consensus clusterings. Experts can explore these different solutions and base their interpretation of predominant flow type on quantitative (objective) criteria.
Authors
Lars Sekse M. Simic R. VidrihAbstract
No abstract has been registered
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Authors
Gayaneh Kyureghian Rodolfo M. Jr. Nayga Suparna BhattacharyaAbstract
No abstract has been registered
Authors
Steffen Adler Annette Veberg Dahl Søren Krogh Jensen Erling Thuen Anne-Maj Gustavsson Håvard SteinshamnAbstract
submittedVersion
Abstract
No abstract has been registered