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.
2002
Forfattere
Anders BrynSammendrag
Det er ikke registrert sammendrag
Forfattere
Erik Næsset Tonje ØklandSammendrag
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.
Forfattere
Kjersti Holt HanssenSammendrag
Det er ikke registrert sammendrag
Forfattere
Gro HylenSammendrag
Det er ikke registrert sammendrag
Forfattere
Bernt-Håvard Øyen Petter NilsenSammendrag
Growth effects in a sub-alpine, low-yield Norway spruce forest in southeast Norway are reported. Sixteen sample plots of 400 m2, established 8-9 years after a mountain forest selective (MFS) cutting in the mid-1970s, were re-investigated in 2000. The selective cutting was heavy, with a mean felling volume of 72 per cent of the standing volume. Most trees in the remaining stands responded positively with increased growth after the cutting, and this was most pronounced in small and medium sized trees. A weak relationship between standing volume before and after felling, and the actual stand volume increment in the 25-year period was revealed. The felling has stimulated natural regeneration and increased the proportion of birch. The results indicate that not more than ~65 per cent of the standing volume should be cut in a single intervention if cutting cycle is less than 50 years.
Forfattere
Oddvar Skre R. Baxter R.M.M. Crawford T.V. Callaghan A. FedorkovSammendrag
Modeling studies indicate that if the global warming persists over centuries, the tundra-taiga boundary will move northwards. However, on a regional scale large variations may exist, and in oceanic areas a southwards retreat may also be expected. This tendency is reinforced by human activity, in particular in northern Russia. Local changes over short periods therefore requires continuous observation and monitoring of treeline movement, from an economic as well as forecology and conservation.
Forfattere
Kjell Andreassen Bernt-Håvard ØyenSammendrag
Six experimental sites in the coastal spruce (Picea abies L. Karst.) forest of central Norway were investigated. A comparison of different silviculture systems was performed based on the present situation of mature stands, and a single tree selection system, a group system and a clearcutting system were studied. The diameter distribution shows the classical inverse J-shaped curve at five of six sites. The mean tree volume removed in the selection system was 0.6 m3, and about 0.3 m3 for the other two methods. The harvesting cost was about 14 Euro/m3 for clearcutting, and about 10% higher for the group and selection systems. In simulations of all future revenues and expenses based on the observed stand conditions, cutting and extraction costs, the net present value (NPV) was app. 15% lower for the group and selection systems compared to clearcutting. A lower stem volume production in uneven-aged stands and higher administration and harvesting costs had only a minor influence on the NPV. One percent higher interest rate lowered the NPV of the group and selection systems to 75% of the clearcutting method.
Forfattere
Lars Sandved Dalen Carl Gunnar Fossdal R. Bhalerao John Beck Jensen Teemu H. TeeriSammendrag
Trees cover over one-third of the world\"s land area and carry out about two-thirds of global photosynthesis. Coniferous forests cover 1.2 billion hectares of Alaska, Canada, Scandinavia, and Russia, and comprise one-fourth of the world\"s boreal and temperate forests. More than 50% of Scandinavia\"s land area consists of forests, mostly coniferous. Information about the molecular responses in trees to biotic and abiotic factors is therefore of great importance - both scientifically and practically. Generation of expressed sequence tags (ESTs) is an important part of genome research. Randomly selected cDNA clones are partially sequenced, and the ESTs reflect the level and complexity of gene expression in the sampled tissue. In order to find interesting gene products and to study gene expression in the most common and economically important conifer in the Nordic countries, we have started an EST-project on Norway spruce. So far we have sequenced ~3500 cDNA clones based on mRNA isolated from needles and cell cultures. Here, we present the frequency of the different ESTs, their putative function and their functional classification. We aim at sequencing another 20,000-30,000 cDNA-clones from wood-forming tissues and from seedlings treated with drought, low temperatures, pathogen infection, etc. The long-term goal is to develop a non-redundant and annotated collection of Norway spruce clones to be used in combination with microarray analysis
Forfattere
Halvor TorgersenSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor MykingSammendrag
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.