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2012

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Sammendrag

The ascomycete fungus Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea) is responsible for ash dieback currently expanding over large parts of Europe. Our objective was to investigate the genetic structure of H. pseudoalbidus and to examine its relationship to the species H. albidus, known as a saprotroph. The study comprised 181 isolates of H. pseudoalbidus collected within the diseased area, 17 H. albidus isolates from six apothecia, collected outside the diseased area in Norway, and nine apothecia of H. pseudoalbidus collected in Sweden. By analysis of microsatellite markers developed for this study, combined with AP-PCR using the M13 primer, we demonstrated sexual heterothally in H. pseudoalbidus, detected high gene flow and low geographic structure of the H. pseudoalbidus population and found indications of a founder effect. Also, substantial genetic differences were detected between the two species of fungi; only four of seven microsatellite markers developed for H. pseudoalbidus were amplified for H. albidus, and no alleles were shared among the species. Furthermore, AP-PCR banding patterns were distinctly different for the two species. We conclude that even though the two fungi have a similar habitat and are morphologically virtually identical, they do not share a recent common ancestor.

Sammendrag

The objective of this paper is to examine a method for estimation of land cover statistics for local environments from available area frame surveys of larger, surrounding areas. The method is a simple version of the small-area estimation methodology. The starting point is a national area frame survey of land cover. This survey is post-stratified using a coarse land cover map based on topographic maps and segmentation of satellite images. The approach is to describe the land cover composition of each stratum and subsequently use the results to calculate land cover statistics for a smaller area where the relative distribution of the strata is known. The method was applied to a mountain environment in Gausdal in Eastern Norway and the result was compared to reference data from a complete in situ land cover map of the study area. The overall correlation (Pearson’s rho) between the observed and the estimated land cover figures was r = 0.95. The method does not produce a map of the target area and the estimation error was large for a few of the land cover classes. The overall conclusion is, however, that the method is applicable when the objective is to produce land cover statistics and the interest is the general composition of land cover classes – not the precise estimate of each class. The method will be applied in outfield pasture management in Norway, where it offers a cost-efficient way to screen the management units and identify local areas with a land cover composition suitable for grazing. The limited resources available for in situ land cover mapping can then be allocated efficiently to in-depth studies of the areas with the highest grazing potential. It is also expected that the method can be used to compile land cover statistics for other purposes as well, provided that the motivation is to describe the overall land cover composition and not to provide exact estimates for the individual land cover classes.