Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2011
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Wood protection in the last century has mainly been based on chemical treatments. Additionally, the type of construction of wooden buildings and the choice of wood species play an important role. Degradation of wood is not only caused by fungi or bacteria but also by insects. Termites have been a potential risk to wooden structures not only in the warmer regions of our continents but also beyond the regions of their natural habitat due to transport of wood. A new treatment, Electro osmotic pulsing technology (PLEOT), has been tested in lab termite tests and fungi tests. The two choice and non-choice termite tests were carried out using different duration of exposure and different initial wood moisture content. The results show growth of mould fungi on untreated wood samples with high initial wood moisture content after 4 weeks of termite testing whereas PLEOT treatment strongly reduced the development of moulds. Termite mortality was high on untreated wood samples with high initial moisture content but not on wood samples with low initial moisture content. This is explained by mould growth on the wetter samples, which termites don\"t tolerate in large amounts. The loss of wood mass due to termite attack could be reduced by using PLEOT. The mortality of termites was higher in test systems with protected wood samples than untreated samples. PLEOT could be used successfully against fungal attack. The treatment reduced on the one hand mould growth in a termite test and on the other hand reduced strongly the attack of brown rot fungi in a lab test.
Forfattere
Kjell Andreassen Nicholas Clarke Jørn-Frode Nordbakken Ingvald Røsberg Volkmar Timmermann Tonje ØklandSammendrag
Rapporten presenterer sammendrag av resultatene for 2010 fra tre overvåkingsprogrammer: “Overvåking av langtransportert forurenset luft og nedbør”, ”Overvåkingsprogram for skogskader” (OPS) og “Program for terrestrisk naturovervåking” (TOV). The report presents results for 2010 from three national monitoring programmes on long-range transboundary air pollution.
Sammendrag
A changing climate will likely influence the selection of tree species in the future, and this may in turn affect the size of the pools and fluxes of carbon. Tree species differ in growth rate, fine-root turnover and quality of litter and tend to produce different types of understory vegetation. In Sweden three tree species (Norway spruce [Picea abies] 43%, Scots pine [Pinus sylvestris] 39% and birch [Betula spp.] 11%) dominate. In the present study we used field experiments in southern Sweden to test if these tree species differed in root distribution and turnover.
Sammendrag
Biodiversity is assumed to have high value for many people, but the necessary preservation also incurs a cost for the forest owner. Typically, studies of this cost are at the stand level, and hence, not very accurate as the cost may vary even within the stand. In this work, we use a 1m×1m grid, generated from LIDAR data, to estimate the cost for harvesting and forwarding. The method could be utilized to calculate compensation, and to select between key woodland habitats to minimise the cost. In three of four test cases, the main cost was reduced harvested volume, but in one case the key woodland habitat also made the harvesting operations more expensive.
Forfattere
Kjell Andreassen Bernt-Håvard ØyenSammendrag
Fourteen Nordic increment functions have been validated by use of with a test data set from long-term research plots in Norway of even-aged, pure stands of Scots pine, Birch and Norway spruce. In selected functions from Denmark, Finland, Norway and Sweden measures of site productivity, mean tree size and various stand characteristics are represented. Different models display both strengths and weaknesses in their predicting ability. Some measures of precision and bias have been calculated and the functions are ranked due to their performance. Basal area increment models for spruce and pine from Sweden, and a Finish volume increment model for birch has the best fit to the Norwegian test data. Some of the growth models developed outside Norway estimate the growth with about the same accuracy as the models frequently used and developed in Norway. The results indicate that forest conditions and traditional even-aged forest management practice in the Nordic countries seem to have small influence on the relative growth of even-aged stands. By careful recalibration of existing functions from other Nordic countries with data from Norway, a reasonable accuracy could be achieved in Norwegian forest with a reduction of the bias.
Forfattere
Bruce Talbot Morten NittebergSammendrag
In the coastal region of Norway, large volumes of relatively inaccessible plantation timber are maturing for harvest. The economic feasibility of accessing much of this timber has limited the level of harvesting activity considerably. Harvesting planners are faced with the classic dilemma of finding the appropriate level of investment in infrastructure, as against inoptimal transportation. In this paper, we present results from a simple deterministic simulation carried out to illustrate the efficiency frontiers of three transport methods, one of which requires a substantial investment in road upgrading. Results depend on assumptions made, but clearly show that in these conditions, upgrading roads for truck+trailer transport should be evaluated on a cases by case basis. Forest road length and condition, public road distance to conversion site, and investment level all play important roles in the decision structure. In the coastal regions, road upgrades would generally need to be justified by benefits other than timber harvesting alone.
Sammendrag
Understanding the driving forces affecting species occurrences is a prerequisite for determining the indicator suitability of crenic plants. We analysed 18 environmental variables in a two-step approach, evaluating their ability to explain the species composition of 222 springs on five siliceous mountain ranges, in central Germany and north-west Czech Republic (49.9°–50.8°N, 10.6°–12.8°E). First, we identified the significant environmental variables in three subsets of spatial, hydrophysical and hydrochemical variables using a forward-selection procedure. We then performed a partial canonical correspondence analysis (pCCA) to estimate the influence of each subset alone, as well as in combinations. We also used a multiple response permutation procedure (MRPP) to compare the five regions with respect to the dissimilarity of their vegetation composition and environmental variables. Hydrochemical factors played a fundamental role in determining the plant community of the investigated springs. Spatial factors, in particular altitude, were correlated with the hydrochemical factors, but were less important. Hydrophysical factors played only a marginal role. More precisely, species occurrence was mainly driven by a gradient of nutrient availability, which in turn reflected the acidity status. This gradient was primarily represented by high Al, Cd, and Mn concentrations in acidic crenic waters, high Ca and Mg concentrations were encountered in circumneutral springs. By comparing the five regions we could show that there are spatial patterns in the vegetation of springs, which provide valuable ecological information on the water quality. We therefore suggest that biomonitoring approaches to vegetation are suitable for revealing the acidity status of springs and their forested catchments.
Forfattere
Helmer BelboSammendrag
The theoretical potential for increased efficiency in early thinning by using accumulating harvester heads was investigated through simulation. Thinning was performed in corridors perpendicular to the strip road in 75 artificially generated stands with varying average tree size and density. The work pattern and work time in the crane work for five sizes of heads, with grapple diameters in the range of 10 to 50 cm, was estimated by the simulation model. The efficiency increased rapidly when the grapple diameter increased from two to four times the average diameter in the harvested stand, reducing the work time per tree by 15 to 50 percent compared to the single tree handling harvester head. Further increases in grapple dimension also increased the efficiency, but not at the same rate. In real work, the efficiency increase by an accumulating harvester head will probably be slightly lower due to less optimal harvesting conditions, operator skills and other non-productive work tasks that are not affected by work method.
Sammendrag
Wood exhibits a highly anisotropic mechanical behavior due to its heterogeneous microscopic structure and composition. Its microstructure is organized in a strictly hierarchical manner from a length scale of some nanometers, where the elementary constituents cellulose, hemicelluloses, lignin, and extractives are found, up to a length scale of some millimeters, where growth rings composed of earlywood and latewood are observed. To resolve the microscale origin of the mechanical response of the macro-homogeneous but micro-heterogeneous material wood, micromechanical modeling techniques were applied. They allow for prediction of clear wood stiffness (Hofstetter et al. 2005,2007, Bader et al. 2010a,b) from microstructural characteristics. Fungal decay causes changes in the wood microstructure, expressed by decomposition or degradation of its components (Côté 1965, Schwarze 2007). Consequently, macroscopic mechanical properties are decreasing (see e.g. Wilcox 1978). Thus, in the same manner as for clear wood, consideration of alterations of wood in a micromechanical model allows predicting changes in the macroscopic mechanical properties. This contribution covers results from an extensive experimental program, where changes in chemophysical properties and corresponding changes in the mechanical behavior were investigated. For this purpose, pine (Pinus sylvestris) sapwood samples were measured in the reference condition, as well as degraded by brown rot (G. loeophyllum trabeum) or white rot (Trametes. versicolor). Stiffness properties of the unaffected and the degraded material were not only measured in uniaxial tension tests in the longitudinal direction, but also in the three principal material directions by means of ultrasonic testing. The experiments revealed transversal stiffness properties to be much more sensitive to degradation than longitudinal stiffness properties. This is due to the degradation of the polymer matrix between the cellulose fibers, which has a strong effect on the transversal stiffness. On the contrary, longitudinal stiffness is mainly governed by cellulose, which is more stable with respect to degradation by fungi. Consequently, transversal stiffness properties or ratios of normal stiffness tensor components may constitute suitable durability indicators. Subsequently, simple micromechanical models, as well as a multiscale micromechanical model for wood stiffness, were applied for verification of hypotheses on degradation mechanisms and model validation.