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
Stein Tomter Gro Hylen Jan-Erik Ørnelund NilsenAbstract
No abstract has been registered
Abstract
Determining the feedbacks between terrestrial biosphere processes and the meteorological drivers (here precipitation and temperature) is crucial to ecosystem research. In this context, the continuous monitoring of the earth surface provides an invaluable basis for investigating the spatiotemporal dynamics in the activity of vegetation in relation to environmental conditions. Here, we seek to identify which patterns of variability in the meteorological drivers dominate the terrestrial photosynthetic activity from monthly to interannual time scales (resp. fluctuation frequencies). We investigate the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) using SeaWiFS observations from 1998 to 2005 and ancillary meteorological variables. A spectralanalysis leads to a global `classification` of the terrestrial biosphere according to prevalent scale dependent dynamics of fAPAR and its relation to the meteorology. A combined subsignal extraction and dimensionality reduction reveals a series of dominant geographical gradients on specific time scales. E.g. we uncover spatially coherent patterns at low frequencies and show where these are induced by precipitation or temperature fluctuations. We also show where high frequency variations (relative to the annual cycle) in fAPAR coincide with corresponding precipitation dynamics. However, we can also identify regions where the variability of fAPAR on specific time scales cannot be traced back to climate and is apparently shaped by other geoecological or anthropogenic drivers. http://www.terrabites.net/fileadmin/user_upload/terrabites/PDFs/Programme_Book_TERRABITES.pdf
Authors
Antti Asikainen Karl Stampfer Bruce TalbotAbstract
Large volumes of spruce-dominated forests established on steep terrain are maturing in western Norway. The level of harvesting needed in utilising these forests calls for investments in cable yarding, processing and transport systems, and updated knowledge on the appropriate technology for Norwegian conditions. In the yarding-processing-truck transport operation, the processor cannot operate if the cable yarding system does not supply trees at a sufficient rate or when the buffer storage becomes full. As a result, the productivity of the whole system is often substantially lower than those of the individual parts in the system. Discrete-event simulation has been applied successfully in the analysis of a wide variety of wood harvesting and transport systems, where the productivities of different parts in the supply chain are interlinked .....
Authors
Lone Ross Gobakken Patricia K. LebowAbstract
Mould growth on coated wood is today a genuine challenge for house owners. Environmentally sound wooden facades with long service lives and acceptable appearance are desired. The objective in this study was to investigate the accumulated mould growth on 13 different wood substrates with 3 surface coating systems by identifying the factors that contribute to the variation and to predict future performance. A generalized linear mixed model was fit to the data with the analysis showing that coating and exposure time both had highly significant influences on mould growth. Further, wood substrate was significant, but comparatively less than coating and exposure time. A smaller coefficient for mould coverage in the beginning of the exposure period gave the panels with one of the coating systems, BAP, a delay in mould growth, and the extrapolated values for years 6-12 indicate a longer aesthetic service life than panels with the two other coating systems. Coated heartwood as wood type was less susceptible to mould growth than coated mixed wood and coated sapwood. Acetylated pine as wood substrate and aspen as wood species had lower resistance to mould growth than the other wood substrates and wood species, respectively.
Authors
Bruce Talbot Nils Egil Søvde H. Fridén Lars WilhelmssonAbstract
This paper builds on findings from the recently finalised work package 3.9 of the EU Indisputable Key project. Three institutes cooperated in developing intricate models spanning from the standing tree to the dispatch yard of a Swedish window manufacturer. Numerous timber properties were assigned to RFID tags, applied to the log at felling by a specially adapted harvester head. Logs were allocated to each of seven sawmills according to their timber properties using an LP based optimisation procedure. Simulation was then used to compare the fate of traced timber throughout the production lines of one of the sawmills and its downstream manufacturers.....
Authors
Peder GjerdrumAbstract
Building, maintaining and operating drying kilns is a heavy economic burden for most sawmills. As a consequence, drying capacity is often a bottleneck. Kilns are generally operated 24 h a day, 7 days a week, so there is no spare time to increase the production. Good planning routines are a prerequisite for short as well as long term operational planning. Most established sawmills have a mixture of batch and progressive kilns, some older, possibly upgraded, others more modern. This offers some flexibility in choosing the right kiln for drying a timber lot of defined quality, but also represents operational challenges. Through the years working in and for the sawmill industry, a spreadsheet model tool was made for analysing kiln capacity. The model is put together to examine the available-to-needed capacity balance in each of thirteen four-week periods of a year. Input values are information about the drying kilns and their operations, the sawmill production plans and the requested drying quality. Capacity is given in volume-hours (calculated in the same way as man-hours). The operational plans, i.e. the input values, can and should be adjusted until a reasonable balance for all periods, summed up in a graph, is achieved. A description of the model with a specified sawmill example will be given, illustrating the process from the initial stage to the final plans.
Authors
Igor A. Yakovlev Carl Gunnar Fossdal Øystein JohnsenAbstract
The temperature level experienced during zygotic embryogenesis in the conifer Norway spruce effects an epigenetic memory and vital phenological traits in the progeny (Kvaalen & Johnsen, 2008). MicroRNAs (miRNAs) are endogenous small RNAs having large-scale regulatory effects on plant development and could participate in epigenetic regulation of expression in plants. To unravel the possible molecular mechanisms behind this epigenetic phenomenon we prepared two concatemerized small RNA libraries representing smallRNAs expressed in plants from seeds obtained after embryogenesis in cold environment and in a warm environment and made a search of conserved miRNAs found in other plant species. Partial sequencing of the libraries allowed identifying of 199 different small RNAs, with predominant length of 21-nt. Among them were 24 novel candidate miRNAs and 4 conserved. Screening of conserved miRNAs allowed confirming additional 17 miRNAs belonged to 11 miRNA families. Most of the miRNA obtained were related to unknown and “no-hit” genes. The expression of 8 conserved miRNAs (pab-miR156c, 159a, 396a,b, 535, 947, 951 and 858) and 9 predicted miRNAs (miR080, 100, 105, 119, 122, 132, 144a,b and 157) showed significant differences in transcript levels between epigenetically distinct plants. Additionally we confirmed that four selected genes PaLPT4, PaGaMYB, PaMYB10 and PaSPB13 regulated by miRNAs pab-miR100, 858, 159a and 156c, may also be involved in epigenetic memory regulation. Our results suggest that Norway spruce miRNAs are composed of a set of conserved miRNAs and a large proportion of novel non-conserved miRNAs with relatively low expression levels. These findings imply that both kinds of miRNAs might be involved or at least affected by the molecular mechanisms underlying the temperature sensitive epigenetic memory in Norway spruce.
Abstract
We investigated concentrations of dissolved organic carbon (DOC) in throughfall and soil solutions at 5, 15 and 40 cm depth in 16 Norway spruce and 2 Scots pine plots throughout Norway between 1996 and 2006. Average DOC concentrations ranged from 2.3 mg/l to 23.1 mg/l and from 1.1 mg/l to 53.5 mg/l in throughfall water and soil solutions, respectively. Concentrations of DOC in throughfall and soil waters varied seasonally at most plots with peaks in the growing season. By contrast to recently reported positive long-term trends in DOC concentrations in surface waters between 1986 and 2003, soil water data from 1996 to 2006 showed largely negative trends in DOC concentrations and no significant trends in throughfall. However, regression analysis for individual sites, particularly at 5 and 15 cm soil depths, showed that DOC concentrations in soil water were significantly and negatively related to non-marine sulphate (SO4) and chloride (Cl-). The lack of a long-term increase in DOC in soil water in the period May 1996 – December, 2006 may be due to the relatively small changes in the deposition of SO4 and Cl- in this period.
Authors
Hans Haavardsholm Blom Louise LindblomAbstract
Degelia cyanoloma (Schaer.) H.H. Blom & L. Lindblom is resurrected from synonymy and elevated from varietal rank to species. The taxon was earlier referred to D. plumbea (Lightf.) P.M. Jørg. & P. James, however, several discontinuous character states distinguish the two species. Degelia cyanoloma is characterized morphologically by having a large thallus that is pale greyish when dry, lobes that are composed of consecutive trough-shaped segments with an upper surface without squamules, no isidia or soredia, and apothecia discs that are dark reddish brown to blackish. Degelia cyanoloma has a euoceanic distribution and is known from western Europe (Norway, France, Great Britain, Ireland, Portugal, Spain). Based on results from studies of morphology, we hypothesize that D. atlantica (Degel.) P.M. Jørg. & P. James is the closest relative of D. cyanoloma among the European species of the genus whereas D. plumbea is closely related to D. ligulata P.M. Jørg. & P. James.
Abstract
Competition for canopy space is a fundamental structuring feature of forest ecosystems and remains an enduring focus of research attention. We used a spatial neighborhood approach to quantify the influence of local competition on the size of individual tree crowns in north-central British Columbia, where forests are dominated by subalpine fir (Abies lasiocarpa), lodgepole pine (Pinus contorta) and interior spruce (Picea glaucax engelmanii).Using maximum likelihood methods, we quantified crown radius and length as functions of tree size and competition, estimated by the species identity and spatial arrangement of neighboring trees.Tree crown size depended on tree bole size in all species. Given low levels of competition, pine displayed the widest, shortest tree crowns compared to the relatively long and narrow crowns found in spruce and fir. Sensitivity to crowding by neighbors declined with increasing tree height in all but the pine crown radius model. Five of the six selected best models included separate competition coefficients for each neighboring tree species, evidence that species generally differ in their competitive effects on neighboring tree crowns.The selected crown radius model for lodgepole pine, a shade-intolerant species, treated all neighbors as equivalent competitors. In all species, competition from neighbors exerted an important influence on crown size. Per-capita effects of competition across different sizes and species of neighbors and target trees varied, but subalpine fir generally displayed the strongest competitive effects on neighbors.Results from this study provide evidence that species differ both in their response to competition and in their competitive influence on neighbors, factors that may contribute to maintaining coexistence.