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.
1992
Forfattere
Erik NæssetSammendrag
Det er ikke registrert sammendrag
Forfattere
Torstein LislandSammendrag
Det er ikke registrert sammendrag
Forfattere
Tore SkrøppaSammendrag
Det er ikke registrert sammendrag
Forfattere
Tore SkrøppaSammendrag
Det er ikke registrert sammendrag
Forfattere
Tore SkrøppaSammendrag
Det er ikke registrert sammendrag
Forfattere
Torbjørn OkstadSammendrag
Det er ikke registrert sammendrag
Forfattere
Jørund RolstadSammendrag
Det er ikke registrert sammendrag
Forfattere
Isabella BørjaSammendrag
Det er ikke registrert sammendrag
Forfattere
Kjell Vadla Gunnar WilhelmsenSammendrag
Det er ikke registrert sammendrag
Forfattere
Kjell VadlaSammendrag
This survey is part of the research program Forest ecology and multiple use. The intent is to show the economic aspects of this kind of production, and in that regard quality of wood is a significant factor. The increment of trees are influenced by genotype and site factors. The density of the stand is one of the site factors with great influence on the increment of trees and the quality of wood. Quality of wood is no unique concept. The evaluation and meaning of the word wood quality depends on the use of the material. Different properties of wood attach different importance by the users. In general, the criteria for wood quality are grouped in the following three categories: Physical: dimension, density, strength etc.Anatomical: knot, ring width, early/late wood etcChemical: content of cellulose, content of lignin etc. When selection cutting is made, regeneration and production of wood are interrelated. Typical selection forest do not include large stands of trees. Instead they consist of quite small units - single trees, clusters and clumps of trees. Even all categories of trees - from seed plants to mature trees - are present in smaller areas. Shelterwood system implies regeneration below a shelter of trees of varying density, regularly scattered throughout the regeneration area. The shelter trees provide seed for the regeneration area as well as protection of the field against drainage and weeds. In addition they protect the seed plants against frost, strong heat and pressure from snow. Furthermore the shelter trees produce wood in the regeneration period. To the majority of the forest industry, sawmills and veneer industry in particular, presence of knots in the wood is a depreciating factor. The number of branches in each branch whorl depend for a small extent on the stand density. The property depends mainly on genetic factors and can only be changed during plant breeding. The dying of branches is influenced by the stand density. In stands with high density, dying of branches will start earlier than in stands with low density. Local conditions and genetic factors are of importance as well. Earlier branch dying implies smaller knots, which in turn will affect the selfpruning. The selfpruning is a complex interaction between various factors. The positive and negative effects of the various factors are evident, but there seems to be no quantitative relation between them. The density is a good indicator of a number of wood properties. Numerous factors influence the density. Considering the site factors, the density of the stand is of most importance. The ring width is greatly influenced by the density of the stand, and subsequently has a considerable influence on the density. In general, the density increases with decreasing ring width, but it can also vary considerably between samples with the same ring width. This variation is mainly due to differences in the content of late wood, which is influenced by site factors and climatic conditions. For the processing industry, especially the cellulose- and pulp industry, the density is of great importance for the evaluation of the wood. The cost of the raw material is based on volume while the marketing price of the finished product is based on weight. The sawmills and the veneer industry prefer wood with high density as well, although it is not of the same importance as for the cellulose- and pulp industry. All organisms follow a certain growth pattern, which is characteristic for the species. The stem form is often characteristic of tree species, but great variations will occur within the species. Furthermore the taper off of the stem will to a large extent be determined by environmental conditions. The density of the stand is of great importance for the stem form. Trees growing in a widely scattered stand will develop a poor stem form compared to trees in a stand with high density. A correlation exists between the stem form and a number of wood properties. The correlation between the stem form and the content of knots is significant. The wood produced when the trees are young, is called juvenile wood. The proportion of juvenile wood in the radial direction varies from one tree species to another. The proportion of juvenile wood is influenced by genetic factors, site factors, site quality class and silviculture. This implies that slowly grown trees develop a cylinder of juvenile wood with a relatively small diameter, while rapidly grown trees develop a larger proportion of juvenile wood. As mentioned at the beginning, the purpose of this survey is to show the economic aspects of Selection cutting and Shelterwood cutting. In that regard quality of wood is an important factor. The production value, or the economy, is related to the production volume as well as to the quality of wood. A reduction in the production volume can be compensated for by higher production quality. The concept quality of wood encompass a number of parameters which have to be determined. This literature search shows that there are very few qualified surveys made on selection- and shelterwood cutting. The basic data for making economic calculations are therefor scarce, and more thorough studies are necessary to make a complete analysis.