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.
2003
Sammendrag
The rationale for stand growth modelling is often either grounded in a search for improved scientific understanding or in support for management decisions. The ultimate goal under the first task is seen in mechanistic models, i.e. models that represent the stand structure realistically and predict future growth as a function of the current status of the stand. Such mechanistic models tend to be over-parameterized with respect to the data actually available for a given stand. Calibration of these models may lead to non-unique representations and unreliable predictions. Empirical models, the second major line of growth modelling, typically match available data sets as well as do process-based models. They have less degrees of freedom, hence mitigate the problem of non-unique calibration results, but they employ often parameters without physiological or physical meaning. That is why empirical models cannot be extrapolated beyond the existing conditions of observations. Here we argue that this widespread dilemma can be overcome by using interactive models as an alternative approach to mechanistic (algorithmic) models. Interactive models can be used at two levels: a) the interactions among trees of a species or ecosystem and b) the interactions between forest management and a stand structure, e.g. in thinning trials. In such a model data from a range of sources (scientific, administrative, empirical) can be incorporated into consistent growth reconstructions. Interactive selection among such growth reconstructions may be theoretically more powerful than algorithmic automatic selection. We suggest a modelling approach in which this theoretical conjecture can be put to a practical test. To this end growth models need to be equipped with interactive visualization interfaces in order to be utilized as input devices for silvicultural expertise. Interactive models will not affect the difficulties of predicting forest growth, but may be at their best in documenting and disseminating silvicultural competence in forestry.
Forfattere
Peder Gjerdrum Olav Albert HøibøSammendrag
Pine heart- and sapwood can in several respects be considered two different timber products, demonstrating separate wood properties. The efficiency of automated heart- and sapwood separation by analysing temperature images of pine crosscuts has been investigated. A digital, infrared (IR) ThermoVisionfocal plane array camera with 320*240 pixels was employed. IR exposures of the front-end crosscut of 180 pine sawlogs were taken during longitudinal transport on a conveyor, arbitrary crosscut being in front. In each image, one arbitrary diameter was chosen for estimating the heart-wood. The temperature gradient between heart- and sapwood was in the range up to 4oC. An algorithm was established to calculate front-end heartwood diameter as a fraction of log diameter. The correlation between estimated and observed heartwood fraction was r = 0.85. Finally, top end heartwood diameter in mm could be calculated by multiplying top-end diameter, as measured in an ordinary log scanner, with heartwood fraction in front (arbitrary) end. For fresh logs RMSE amounted to 11 mm (front: top end) and 15 mm (front: arbitrary end), respectively. It was concluded that the method might be applicable for an industrial log sorting system and might have a potential to indicate even other wood characteristics. The temperature gradient between heart- and sapwood showed to be a reliable criterion for the accuracy of the model. The temperature gradient might even be used to indicate log freshness.
Forfattere
Peder GjerdrumSammendrag
Knowledge about the transformation of sapwood into heartwood contributes to the understanding of the nature of pine trees and should be considered prior to the conversion of sawlogs to produce timber of prescribed properties and optimal revenue. In this study, heartwood formation was ascribed to the joint effect of ageing and growth rate. Observations of heart- and sapwood in 1656 trees and sawlogs of Scots pine (Pinus sylvestris L.), sampled throughout Scandinavia, were analysed using mixed models. The most important finding was expressed in the pine heartwood age rule: heartwood age equals the square root of cambial age less three, to the second power. This global formula was valid irrespective of environmental factors and location within the tree, and described 93 per cent of the variance in the sample. Transition rate increases from 0.6 rings a−1 at 50 years to 0.8 rings a−1 at 200 years. The spatial amount of heartwood might be influenced by the silviculture through the annual ring width pattern. For samples missing sapwood, e.g. archaeological wood, the results might be combined with dendrochronology in specimen dating. When the diameter and the heartwood diameter of sawlogs were known, the mean annual ring width could be estimated with a standard deviation of 0.5 mm a−1. The simplicity, consistency and high correlation of the pine heartwood age rule confirms the importance of age as the main factor in heartwood formation.
Sammendrag
Areas near the Norwegian-Russian border are being strongly contaminated by heavy metal emissions from copper-nickel smelters in the Kola peninsula. The present report presents data for the four elements arsenic, chromium, cobalt, and selenium in vegetation sampled in eastern Finmark, obtained by neutron activation analysis. It is no doubt that the smelters in Nikel and Zapolyarny, constitute the main source of these elements in this area. Some chromium comes from local domestic sources. Still, however, the concentration of these elements in soil and vegetation are probably too low as such to represent any harm to the ecosystem.
Forfattere
Peder GjerdrumSammendrag
The timber industry in Norway is quite fragmented. Several small-scale and a few medium-sized sawmill add up to an annual production of 2.5 mill. m3. Since three decades, most of the timber is kiln dried. Modern kilns and enhanced modelling contribute to improved drying quality and increased drying speed. However, due to harsh competition, fast dried, inferior drying quality timber is continually being offered and accepted for trade in the European area. This might put the overall goodwill for timber at hazard in the long run. Unfortunately, the detection of drying quality properties is quite complex. In this situation, industry and RTD-bodies like the Norwegian Forest Research Institute co-operate to offer competence-building activities. Seminars in wood drying and related topics are offered mainly on a corporate basis, thereby introducing an intimate atmosphere for dealing with these cautious topics. A fixed number of participants meet regularly for two day\"s of intensive work over a period of two or three years. The seminars typically include persons from all levels of the factory organisation, incorporating salesmen, mill operators and maintenance together with kiln operators, sometimes also bringing inn external customers. Work alternate between practical experiments, presentations and training. The activity is continued in working groups between the meetings. All seminars are adequately reported with respect to findings, thereby enhancing the business value of the achievements. The seminars also provide an invaluable basis for research projects and for recruiting fresh candidates. For the institute, this symbiosis with industry helps keeping focus on factors influencing profitability in the timber business.
Forfattere
Morten Ingerslev Inge Stupak Møller Karsten Raulund-Rasmussen Ingeborg Callesen Vivian Kvist JohannsenSammendrag
Det er ikke registrert sammendrag
Forfattere
Bjørn ØklandSammendrag
Det er ikke registrert sammendrag
Forfattere
Øystein Johnsen Carl Gunnar Fossdal Rüdiger Baumann Jørgen A. Mølmann Ola Gram Dæhlen David Clapham Tore SkrøppaSammendrag
Det er ikke registrert sammendrag
Forfattere
Petter Nilsen Gunnar AbrahamsenSammendrag
Results from two fertilizer experiments in coniferous forest in south and southeast Norway with applications of nitrogen (N), magnesium (Mg) and phosphorous (P) are presented. A Scots pine stand has been fertilized annually for 9 years and one Norway spruce stand has been fertilized annually for 4 years. The aim of the study has been to investigate to what extent N fertilization in middle-aged stands of Scots pine and Norway spruce stimulates tree growth, and whether Mg and P counteract possible induced nutrient imbalances caused by high N doses. Both stands responded strongly to N addition and application of 30 and 90kgNha-1yr-1 resulted in a relative volume increment of 150 and 250%, respectively, compared to control. The increment effect in the pine experiment ceased after 4 years, but the difference between the two N doses was still significant after 9 years. The application of 1.5kgMgha-1yr-1 had just a slight significant positive effect on volume increment in two of the 9 years in the pine experiment, while no effect of 5.3kgPha-1yr-1 on volume increment was found. Needle nutrient concentrations were mainly affected by the N treatment and concentrations above 30mgg-1 was detected in the pine experiment. The concentration of P, Mg and K was negatively affected by the highest N dose in the spruce experiment, but not in the pine experiment. The imbalanced nutritional status created by N application was partly reduced by the P and Mg addition, but no substantial effect on tree growth has been detected so far. The stands have a large potential for accumulating N in the standing biomass and judged from the effect on nutrient concentrations and growth, Mg might be the next element that could limit tree growth by a continued high N atmospheric input.
Forfattere
Live S. Vestgarden O. Janne KjønaasSammendrag
The objective of this study was to quantify the net potential N mineralisation and nitrification rates in mineral soils of two coniferous forest soils subjected to different N additions. One study site was located at Åmli (Pinus sylvestris L. forest), southern Norway and another at Gårdsjön (Picea abies forest), southwestern Sweden. Mineral soil was collected from 14 to 19 and 24 to 29 cm depth in May at Gårdsjön and in May, July, September and November at Åmli. The soil was incubated in the dark at 15 °C for 2 months in the laboratory, and the NH4+ and NO3- content were compared relative to pre-incubated values. The initial contents of NO3- and NH4+ in the soil at the two sites were of about the same magnitude, but the potential net N mineralisation, ammonification and nitrification rates differed significantly. At Gårdsjön, the net N mineralistion ranged from 6 to 29 mg N kg-1 per 2 months, whereas a net N immobilisation generally occurred at Åmli. Additions of 0–50 kg N ha-1 per year had no effect on the transformation rates at the two sites. Applications of large single doses of 90 kg N ha-1 per year during the last 8 years have significantly increased the net nitrification rate in the soil at Åmli. However, a net N mineralisation was only observed in the soil 1 month after the N addition. At low N input levels, site-specific factors, such as the content of organic matter, clay, and moisture, seemed to a large degree to determine the transformation rates. Large spatial variability both within catchments and between catchments at Gårdsjön may have obscured the effects of small N inputs.