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.
2002
Authors
Erik Næsset Tonje ØklandAbstract
No abstract has been registered
Authors
Erik Næsset Tonje ØklandAbstract
Tree height, the height from the ground surface to the tree crown, and the crown length as a proportion of tree height of individual trees were derived from various canopy height metrics measured by a small-footprint airborne laser scanner flown over a boreal forest reserve. The average spacing on the ground of the laser pulses ranged from 0.66 to 1.29 m. Ground-truth values were regressed against laser-derived canopy height metrics. The regressions explained 75%, 53%, and 51% of the variability in ground-truth tree height, height to the crown, and relative crown length, respectively. Cross-validation of the regressions revealed standard deviations of the differences between predicted and ground-truth values of 3.15 m (17.6%), 2.19 m (39.1%), and 10.48% (14.9% of ground-truth mean), respectively. On 10 plots with size 50 m2 in the boreal forest reserve and on 27 plots with size 200 m2 in a managed spruce forest, mean tree height, average height from the ground surface to the crown, and average relative crown length were regressed against laser canopy height metrics. The coefficients of determination (R2) ranged from .47 to .91. Cross-validation revealed a precision of 1.49 m (7.6%), 1.24-1.52 m (20.9-23.3%), and 6.32-7.11% (8.8-10.9% of ground-truth mean) for mean tree height, average height to the crown, and average relative crown length, respectively. At least, mean tree height can be determined more accurately from laser data than by current methods.
Authors
Tor MykingAbstract
Additive variation in adaptive traits is a prerequisite for selection and adaptation to future environmental changes, but distribution of adaptive genetic variability between and within populations is poorly known in most forest trees. Owing to this deficiency, life history traits such as geographic range, pollination vector and seed dispersal capability, which significantly affect gene flow and thus the distribution of genetic variability, were used to evaluate the genetic resources in 23 Norwegian native forest tree species. Based on the combination of life history traits the species\" genetic resources were classified either as viable, potentially vulnerable or vulnerable, assuming a decrease in within-population variability in this sequence. Twelve widely distributed species with generally effective dispersal of pollen and seeds were considered viable (Pinus sylvestris, Picea abies, Juniperus communis, Betula pubescens, B. pendula, Alnus incana, A. glutinosa, Salix caprea, Populus tremula, Corylus avellana, Sorbus aucuparia, Prunus padus) and have as such no particular conservation needs. Effective seed dispersal of these species, as inferred from post-glacial migration rates, may be partly responsible for their generally early post-glacial appearance, and may, in combination with the wide ranges and relatively large evolutionary potential, indicate that viable species are best able to cope with climatic change. Among species with restricted ranges and more limited gene flow eight were considered potentially vulnerable (Quercus petraea, Q. robur, Fraxinus excelsior, Acer platanoides, Taxus baccata, Ilex aquifolium, Fagus sylvatica, Ulmus glabra) and three were considered vulnerable (Tilia cordata, Malus sylvestris, P. avium). Application of different intensities of a multiple population breeding system (MPBS) is considered the most appropriate mode of conserving genetic resources in these species.
Authors
Halvor Torgersen Torstein LislandAbstract
No abstract has been registered
Authors
Erlend Ystrøm Haartveit Dag FjeldAbstract
Two games, called “Wood Supply Games”, are developed based on the structure and dynamics of the Beer Game. The games are intended as student exercises in forestry logistics courses. By introducing divergent and convergent flows in the supply chain, the relevance to the forest sector is increased. Results from pilot experiments of the games are presented and discussed in terms of how different degrees of complexity in supply chain structures may affect their efficiency. Measures of efficiency are accumulated costs, amplification of demand and the sample variance of order rates. Results indicate that supply chain performance is negatively affected by increasing rigidity of constraints at points of divergence. Furthermore, lower degrees of efficiency and predictability are observed as complexity of supply chain structure increases. Testing of results and proposed hypotheses can be accomplished by running numerous replications of the games, or alternatively, by development of appropriate simulation models.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Norwegian fluid milk consumption has declined steadily over the last twenty years, despite the dairy industry spending increasing amounts of money on advertising. Using a two-stage model, we investigate whether advertising has increased the demand for milk. No effect of advertising on the demand for non-alcoholic beverages is found in the first stage. In the second stage, an almost ideal demand system including advertising expenditures on competing beverages is estimated. The effects of generic advertising within the beverage group are positive and significant for whole milk and negative and significant for lower fat milk. The own-advertising elasticity for the combined fluid milk group is 0.0008. This highly inelastic elasticity suggests that increased advertising will not be profitable for the producers. Several cross-advertising effects are statistically significant, emphasizing the usefulness of a demand system approach.
Authors
Dan AamlidAbstract
No abstract has been registered
Authors
Tore SkrøppaAbstract
No abstract has been registered