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.
2010
Authors
Arild Andersen Trond Hofsvang May Bente Brurberg Christer Magnusson Trond Rafoss Brita Toppe Anne Marte Tronsmo Bjørn Økland Leif SundheimAbstract
No abstract has been registered
Authors
Arild Andersen Trond Hofsvang May Bente Brurberg Christer Magnusson Trond Rafoss Anne Marte Tronsmo Bjørn Økland Leif SundheimAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Ana Maria Barata da Silva Åsmund Asdal Elinor LipmanAbstract
No abstract has been registered
Authors
Mari Mette Tollefsrud Christoph SperisenAbstract
Norway spruce (Picea abies [L.] Karst.), one of the most important species of the boreal forest, is found naturally distributed in two disjunct ranges; one northern and one southern European range. These ranges have been shown to correspond to two genetically distinct lineages. In this talk, results on the genetic structure based on mitochondrial DNA (mtDNA; nad1) and nuclear microsatellites in populations from the northern European lineage, will be presented and discussed in the light of its glacial and postglacial history. The genetic relationship between Norway spruce and its will closest relative Siberian spruce (Picea abovata Lebed.) will also be discussed based on results from mtDNA and paternally inherited chloroplast DNA (cpDNA). Genetic structure of northern European Norway spruce is generally shallow, consistent with recently compiled pollen data, suggesting that Norway spruce in Northern Europe was colonized from a single Russian refugium. Despite the low differentiation found, the structure at both mtDNA and nuclear DNA suggest that expansion westwards took place along two main migration routes; one northwestern over Finland to northern Scandinavia, and one southwestern across the Baltic Sea into Scandinavia. Based on both mtDNA and nuclear DNA, populations in the oldest regions of Russia and the Baltic States show the highest diversity. Based on pollen data, colonization of these regions took place at high population densities, helping to maintain high levels of diversity. Also populations in southern Sweden and southern Norway show relatively high levels of diversity compared to the more northern Scandinavian populations. This may be due to the additional southern migration route into the region, as well as pollen-mediated gene flow in the south which seems to efficiently have replenished the loss of nuclear diversity following postglacial colonization. In the northern part of Fennoscandia, smaller effective population size due to more limited seed and pollen production may have caused decreased nuclear diversity and increased inbreeding, reflecting the ecological marginality of the species in the north. Genetic differentiation between Norway spruce and Siberian spruce based on mitochondrial and chloroplast markers suggest that the border between the two species occur east of the Ural Mountain, following the river Ob. Still, the paternally inherited cpDNA marker suggests extensive introgression from Siberian spruce into the northern European range of Norway spruce. Introgression via pollen may thus acts as a mechanism of dispersal of Siberian spruce genes into the northern European gene pool of Norway spruce.
Authors
Laura Parducci Mari Mette Tollefsrud Sonia L. FontanaAbstract
Previous fossil evidence suggests that small Picea abies populations were present in Scandinavia prior to the general expansion of the species in the peninsula during the last 3000 years. In this study we identified a novel polymorphic region of the Picea abies mitochondrial genome with two variants caused by an insertions-deletion of 20 bp. We used this variant to characterize the genetic variation of a 7000-years-old population of Picea abies using pollen retrieved from a Holocene lake sediment situated in central Norway. Comparison of ancient patterns of genetic variation with modern patterns observed in extant populations sampled over the North European range of the species helped us to answer several important questions regarding the spread of this species in Scandinavia after the last glaciation.
Authors
Tuula Kantola Mikko Vastaranta Xiaowei Yu Paivi Lyytikainen-Saarenmaa Markus Holopainen Mervi Talvitie Sanna Kaasalainen Svein Solberg Juha HyyppäAbstract
Climate change has been observed to be related to the increase of forest insect damages in the boreal zone. The prediction of the changes in the distribution of insect-caused forest damages has become a topical issue in the field of forest research. The common pine sawfly (Diprion pini L.) (Hymenoptera, Diprionidae) is regarded as a significant threat to boreal pine forests. Defoliation by D. pini caused severe growth losses and tree mortality of Scots pine (Pinus sylvestris L.) (Pinaceae). Logistic regression is commonly used in modelling the probability of occurrence of an event. In this study the logistic regression was investigated for predicting the needle loss of individual Scots pines (pine) using the features derived from airborne laser scanning (ALS) data. The defoliation level of 164 trees was determined subjectively in the field. Statistical ALS features were extracted for single trees and used as independent variables in logistic regression models. Classification accuracy of defoliation was 87.8% as respective kappa-value was 0.82. For comparison, only penetration features were selected and classification accuracy of 78.0% was achieved (kappa=0.56). Based on the results, it is concluded that ALS based prediction of needle losses is capable to provide accurate estimates for individual trees.
– Comparing canopy penetrating of repeated ALS acquisitions
Svein Solberg, Erik Næsset, Holger Lange
Abstract
The airborne laser scanning (ALS) penetration rate, i.e. the ratio of ground echoes to total echoes, is a proxy for gap fraction. Hence, ALS has a potential for monitoring forest properties that are related to gap fraction, such as leaf area index, canopy cover and disturbance. Furthermore, two gap types may be distinguished: While a pulse that only produces a ground echo most likely hit a large, between-tree gap, a pulse that produces a ground echo as the last of several returns most likely hit smaller, within-canopy gaps. This may be utilized to distinguish between disturbance types such as defoliation and tree removal. However, the ALS penetration rate needs to be calibrated with gap fraction measurements in the field, because it is influenced by technical properties of the acquisition. The aim of this study was to quantify the magnitude of this influence, by comparing repeated acquisitions with different technical specifications. We had at hand 12 ALS acquisitions which could be combined into six pairs, from four spruce and pine dominated forests in Norway. We established 20x20 m grids, and for each grid cell we extracted three penetration variables: first echo penetration, last-of-many echo penetration, and total (i.e., first and last echo). We log-transformed the penetration variables (P1 and P2) from two laser acquisitions, and fitted the no-intercept, linear model log(P1) = log(P2), applying total least squares regression analysis. In a majority of the cases, the penetration variables were very similar, i.e. they deviated by <10%. For the first echo penetration the slopes varied from 0.87 to 1.07 and the R2 values ranged between 0.91 and 0.99. For the last-of-many echo penetration, there was generally weaker correspondence with slopes varying from 0.78 to 1.02, and R2 values ranging from 0.60 to 0.94. Finally, for the total penetration there was again stronger agreement with slopes in the range 0.83-1.03 and R2 values from 0.88 to 0.99. In conclusion, it seems that the penetration ability of different ALS scans in many cases are very similar, and further research may reveal ranges of standardized settings for which field inventory can be redundant.
Authors
Grete StokstadAbstract
No abstract has been registered
Abstract
No abstract has been registered