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.
2014
Sammendrag
No abstract has been registered
Sammendrag
No abstract has been registered
Sammendrag
No abstract has been registered
Forfattere
Erik J. JonerSammendrag
No abstract has been registered
Sammendrag
No abstract has been registered
Sammendrag
No abstract has been registered
Sammendrag
Ari M. Hietala, Volkmar Timmermann, Isabella Børja & Halvor Solheim Norwegian Forest and Landscape Institute. PO Box 115, 1431 Ås, Norway: ari.hietala@skogoglandskap.no Owing to the Gulf Stream, the northernmost European populations of several tree species are found in Norway. Common ash (Fraxinus excelsior), the only native ash species in Norway, is present in the lowlands in the southeastern part with continental climate and in southern and southwestern coastal regions with North Atlantic climate up to Central Norway. The current standing volume of ash in Norway is ca 3 mill m3 (broadleaved trees in total 220 mill m3). The first documentation of Ash Dieback (ADB) is from 2008 from a nursery in the southeastern part of the country. A survey later that year showed that dieback symptoms were present over a distance of nearly 400 km in the southeastern region. In addition to nurseries and forests, ADB symptoms were observed on roadside, alley, garden and park trees. Based on the presence of old ADB-like stem lesions detected in 2008, the pathogen must have arrived to Norway no later than 2006. In 2008, the Norwegian Food Safety Authority laid down regulations with the aim of preventing further spread of ADB. These regulations divide the country into quarantine, observation and infection-free zones, and prohibit the export of ash seedlings, seed and wood from the quarantine zone. Despite of these regulations, the disease spread rapidly along the western coast in the period between 2009 and 2013, and currently only the ash stands in Central Norway are free of the disease. The rapid spread of the disease in Norway is obviously due to airborne dispersal of pathogen ascospores. In our experimental stand in SE Norway the number of pathogen fruit bodies can be as high as 10,000 per m2 in the peak season, mid-July to mid-August. During the early morning hours the amount of pathogen ascospores at a diseased stand can exceed 100,000 ascospores per m3 air. The first symptoms of the disease, necrotic lesions on leaf blade and petiole, appear typically during the first two weeks of August in SE Norway. To observe long-term impacts of ADB, eight monitoring plots have been established in continental and North Atlantic climate zones. In SE Norway with the oldest disease history, above 60 % of the trees with a breast height diameter (BHD) below 12.5 cm have so far died or suffer from severe defoliation, 1/3 of the larger trees being affected to a similar degree. The proportions of healthy (no signs of defoliation) small and larger trees are 20% and 37%, respectively. In SW Norway with more recent disease history a similar trend is observed but the proportion of dead trees is still small. As a consequence of ADB, the Norwegian nurseries no longer grow ash seedlings. There are currently no practical control options for the disease in forestland. Several European countries have reported that even at heavily diseased ash stands there are often some ash trees that show little symptoms. This may be due to genetic variation between trees in disease resistance, a hypothesis that is currently being investigated in several European projects. Thus implementation of forest management practices that eliminate ash could have a negative effect as survival of the tree ultimately depends on selection of trees with increased disease resistance. Bibliography for Ari M. Hietala Ari M. Hietala is a Senior Forest Pathologist at the Norwegian Forest and Landscape Institute, which is a primarily government funded organisation providing scientific research and services to government, non-governmental and commercial organisations. He has worked with a range of fungal root and shoot diseases occurring on broadleaved trees and conifers indigenous to the Nordic countries. Ari and the rest of the group participate currently in several European consortia engaged in ash dieback research.
Forfattere
Peder GjerdrumSammendrag
No abstract has been registered
Forfattere
Mari Mette Tollefsrud Yoshiaki Tsuda Jørn Henrik Sønstebø Małgorzata Latałowa Laura Parducci Thomas Källman Jun Chen Vladimir Semerikov Tore Skrøppa Giovanni Guiseppe Vendramin Christoph Sperisen Martin LascouxSammendrag
During the Last Glacial Maximum, the boreal vegetation was greatly restricted. Climatic variation between regions had different impact on the glacial and postglacial history of tree species, resulting in contrasting distribution of genetic diversity. Norway spruce (Picea abies) and Siberian spruce (P. obovata) are two closely related species which parapatric ranges cover almost the entire boreal region of Eurasia; a vast region that experienced contrasting glacial histories. In the present study we combined extensive paleobotanical and genetic data to reconstruct the joint histories of the two species and to evaluate how their glacial and postglacial histories have affected their genetic structure. Today, Norway spruce and Siberian spruce are clearly genetically differentiated in mitochondrial (mt) and nuclear SSR markers, suggesting that the two species had largely independent glacial histories. Nuclear SSR markers indicate the presence of hybrid individuals on both sides of the Urals and east-west longitudinal genetic structures indicate a wide zone of hybridization. The border for mtDNA is situated along the Ob River in Siberia. Along this river and eastwards, latitudinal genetic structures were weak. In Norway spruce, rather complex population genetic structures are revealed as a result of multiple refugia and contrasting recolonization patterns. The current distribution of Norway spruce is divided into a southern and a northern domain. Coherent with the paleodata, both mtDNA and SSR loci suggest a long lasting separation between these two domains, which however, did not preclude secondary contacts. Within the southern domain, mtDNA and paleodata suggest the presence of several refugia, a pattern that nuclear SSR loci fail to reveal probably reflecting pollen mediated gene flow. In the northern domain, the same data support the recolonization of Scandinavia during the mid Holocene from a large and scattered refugium located on the East European Plain. Recolonization took place along different migration routes, and diversity evolved differentially along these routes. The complex genetic structure at nuclear SSRs in the northern Norway spruce domain may be due to gene flow from the southern domain, gene flow from the hybrid zone along the Ural Mountains and expansion from a separate refugium along the Atlantic coast. The latter is suggested by ancient DNA, the presence of a Scandinavia endemic mitochondrial haplotype and possibly, the current structure at SSR loci, where the origin of a distinct genetic cluster in Central Scandinavia remains to be elucidated. The implications of these findings for the response of the boreal forest to climate, forest management and breeding will be discussed.
Forfattere
Theo RuissenSammendrag
No abstract has been registered