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.
1995
Forfattere
Sverre SkoklefaldSammendrag
Hensikten med undersøkelsen var å registrere foryngelsesresultatet i frøtrestillinger av furu under varierende forhold, særlig med hensyn til gjenvekstens tetthet og høydeutvikling. En analyse av frøtrærnes diametertilvekst i brysthøyde, før og etter foryngelseshogstene inngår også i undersøkelsen. Undersøkelsen omfatter i alt 16 frøtrestillinger med 7 i lavskog, 3 i røsslyng-blokkebærskog, 5 i bærlyngskog og ett i blåbærskog. Frøtreantallet varierte fra 20-128 pr. ha, og høyde over havet fra 150-850 m. Ni av feltene var markberedte, 1-10 vegetasjonsperioder etter foryngelseshogstene. Registreringen ble utført 6-24 vegetasjonsperioder etter frøtrestillingshogstene. Humustykkelsen varierte da fra 2.4-3.4 cm i lavskog, 2.8-4.4 cm i bærlyngskog og 5.7-7.1 cm i røsslyng-blokkebærskog. Blant felter som ikke ble markberedt, hadde det høyestliggende (lavskog, 850 m o.h.) kun 550 planter pr. ha med nullruteprosent 82 ved registreringen 24 vegetasjonsperioder etter foryngelseshogsten. De øvrige, ikke markberedte felt (3 i lavskog, 2 i røsslyng-blokkebærskog og 1 i blåbærskog) lå i klimatisk gunstige områder (150-330 m o.h.). Seks til 16 vegetasjonsperioder etter hogst varierte nullruteprosenten fra 2 til 26 og planteantallet fra 5360 til 26380 pr. ha. Samtlige 5 felt i bærlyngskog (200-540 m o.h.) var markberedt. Fem til 8 vegetasjonsperioder etter markberedning varierte nullruteprosenten fra 6 til 18 og planteantallet fra 12480 til 23480 pr. ha. To av disse feltene ble markberedt hhv. 8 og 10 vegetasjonsperioder etter frøtrestillingshogstene. Markberedning i lavskog (320-550 m o.h.) gav dårligst resultat. Seks til 9 vegetasjonsperioder etter markberedning varierte nullruteprosenten fra 49-54 og planteantallet fra 2450 til 4130 pr. ha. Etter hvert vil trolig nullruteprosenten synke, bl.a. fordi gjengroing av markberedningsflekker skjer langsomt på denne vegetasjonstypen. Bartreplantenes høydespredning var stor for samtlige felts vedkommende, antagelig som følge av varierende innslag med forhåndsgjenvekst og flere frøår i foryngelsesperioden, men også fordi planter av samme alder har ulike vekstvilkår. Både økende frøtreantall og stigende høyde over havet reduserer furuplantenes høydevekst, men materialet gav ikke grunnlag for å estimere effekten av disse faktorer. På høytliggende markberedte felter (480-550 m o.h.) var imidlertid høydeveksten svært beskjeden i startfasen på næringsfattig mark (lavskog og røsslyng-blokkebærskog). Plantehøyder på ca. 25-35 cm ble først nådd etter 8 vegetasjonsperioder, selv i glisne frøtrestillinger (26 trær pr. ha). Særlig i lavskog reduseres furuplantenes vekst i frøtrærnes nærmeste omgivelser. Med økende avstand vokste plantene raskere, og høydeforskjellen mellom planter i ulike avstander økte med tiden. Etter foryngelseshogstene økte frøtrærnes årlige diametertilvekst med 100% eller mer i 11 av 16 frøtrestillinger. Selv etter 15-16 år var årlig tilvekst større enn i en 20-årsperiode før hogst.
Forfattere
Anders Göransson Toril Drabløs EldhusetSammendrag
The effects of aluminium on plant nutrition in small birch plants (Betula pendula Roth) were investigated. By using relative addition rate (r A, g g-1 d-1) of nutrients as the growth-controlling variable, it was possible to grow the plants at very low external nutrient concentrations and to simulate plant requirements at two different fertility levels.Before aluminium addition the plants were at steady-state relative growth rate, (R G, g g-1 d-1). The two addition rates were free access of nutrients with RG 0.215 d-1, or nutrient-limited, RA and R G= 0.10 d-1.Internal concentrations of calcium and magnesium decreased with increasing Al3 conncentration in the nutrient solution while nitrogen concentrations in the plants remained unchanged or increased. It was demonstrated in both nutrition treatments that calcium and magnesium decrease per se does not reduce plant growth and that uptake has to be considered in relation to plant requirement at different growth rates. The interpretation of the effects of aluminium on Ca and Mg uptake and plant biomass development suggested that processes other than disturbances in Ca and Mg uptake are the cause of the decrease in growth.
Forfattere
Dan AamlidSammendrag
Det er ikke registrert sammendrag
Forfattere
Aksel GranhusSammendrag
Det er ikke registrert sammendrag
Forfattere
Birger Eikenes Bohumil Kucera Frode Fjærtoft O.N. Storheim Geir Isak VestølSammendrag
The project Quality of wood with selection cutting and shelterwood cutting is one of the projects in the research program Forest ecology and multiple use. The purpose has been to analyse wood quality in uneven-aged forests. The material originates from seven experimental plots with selection forests. Of these plots two are located in Nordland, three in Nord-Trndelag, one in Oppland, and one in stfold. Five mature trees were harvested from each plot. The sample trees should be big enough to give sawnwood of the dimension 50x200 mm from the butt log, 50x150 mm from the second log (the middle log), and 50x100 mm from the third log (the top log). The project is divided into three parts:Detailed analyses of annual growth ring width and density were done on trunk discs from different tree heights.Mechanical, technological, and physical properties were measured on small, clear specimens together with anatomical characteristics.Timber in standard structural sizes was sorted both visually and mechanically before testing for modulus of elasticity and static bending strength in the laboratory. At stump height (1 % of tree height) mean annual growth ring width increases from 0.7 mm near the pith to 2.6 mm near the bark. The rate of increase in annual growth ring width is strongest near the pith, and declines towards the bark. Basic density is showing the opposite development, and declines from ca 450 kg/m3 near the pith to ca 350 kg/m3 near the bark. In 20, 40, 60 and 80 % of tree height it was found very small variations in density from the pith towards the bark. Mean basic density for the different experimental plots varies from 350 kg/m3 to 379 kg/m3. Mean for the whole material is 365 kg/m3. The corresponding figures for annual growth ring width show variation in mean values for the plots from 1.38 mm to 2.01 mm, with a mean for the whole material of 1.64 mm. For small, clear specimens the following mean values were found: Modulus of elasticity in static bending 13.4 GPa, static bending strength 79.9 MPa, compression parallel to grain 39.7 MPa, impact bending strength 35.9 kJ/m2, and static hardness in radial direction 2281 N, in tangential direction 2014 N, and in longitudinal direction 2741 N. Standard structural timber was sorted visually and in two different types of stress grading machines. Mean modulus of elasticity is calculated to 11.4 GPa, and mean static bending strength to 42.0 MPa. Results from the present material show that selection forests dont have the same development in annual growth ring width and density as spruce planted on high site index in Eastern and Western Norway. At stump height the annual growth rings near the pith are very narrow, and the growth rings are getting wider towards the bark. Basic density shows the opposite development. Near the pith basic density is high, and it declines towards the bark.Of the experimental plots at our disposal six plots of a total of seven were localized far north or at high altitudes, and therefore the plots are less representative for the main productive spruce forest areas in Norway. Besides, the site index is considerably lower for the present material from selection forests than the materials used for comparison (G11-17 against G23-26). Still we can conclude that wood quality from these experimental plots of selection forests show more uniform annual growth ring width and density, both in stem cross section and in tree height than wood from planted forests. It is not possible to separate juvenile wood on the basis of density and annual growth ring width in wood from selection cutting. Even if the stem form is not specially good, the analyses show that it is possible to get very good wood quality, particularly regarding strength properties, in selection forests which are near the timber line of the natural growth area for spruce in Norway.
Forfattere
Bjørn ØklandSammendrag
Det er ikke registrert sammendrag
Forfattere
Ketil KohmannSammendrag
Denne undersøkelsen er foretatt for å gi svar på et stadig tilbakevendende spørsmål: Hvilken plantetype er skogbruket best tjent med. Med dagens dyrkingsteknikk kan pluggplanter lages på en rekke ulike måter,- med ulike dyrkingsformer, pottebrett, og med ulik intensitet i dyrkingen, bruk av veksthus i hele eller deler av dyrkingsperioden, styrt indusering av veksthvile på høsten m.m. En type pottebrett gir derfor nødvendigvis ikke en helt klart definert plantetype. Undersøkelsen består av tre ulike serier av forsøk. Den første serien består av syv felt med plantetyper som avviker en del fra ordinære plantepartier med hensyn på høyde og alder. Av denne serien trekkes den konklusjon at granplantene ikke må være for små ved utplanting. Hovedårsaken til avgang i denne serien er snutebillegnag og beiting av sau. Den andre og tredje serien består av elleve felt i tre fylker. Her kommer frem at den ettårige pluggplanten med hele dyrkingstiden i veksthus har lavest overlevelse. Mellom de øvrige plantetyper, toårig M95, 2/2 barrot og toårig M60 er det ikke sikre forskjeller. Mens barrotplantene har høyest overlevelse på feltene i Telemark, er det de to-årige pluggplantene (M95 og M60) som overlever best i Vestfold og Buskerud. I alle forsøk er de toårige M60-plantene høyest ved forsøkets slutt.
Rapport/avhandling – Artsmangfold og virkesproduksjon i sydøst-norske naturskoger
Jogeir N. Stokland
Forfattere
Jogeir N. StoklandSammendrag
Det er ikke registrert sammendrag
Forfattere
Wenche E. DramstadSammendrag
Det er ikke registrert sammendrag
Forfattere
Tron EidSammendrag
Non-productive forest land is defined by a potential yield capacity of less than 1.0 m3/ha/year inclusive bark. The portion of non-productive forest areas in stands are usually recorded subjectively in practical inventories. The aim of this work has been to develop sampling methods which, as fare as possible, are based on objectivity. The problems related to non-productive forest areas are restricted to sites with occurrences of rock on surface, shallow soils and obvious productive areas within stands. Non-productivity in wetland areas and mountain areas was not considered. Three different methods for estimation of the portion of non-productive areas were investigated. Method 1 was based on an assumption of a link between actual and expected number of trees per ha, and the portion of non-productive area in stands, i.e. missing trees were assumed to be a result of non-productivity. Method 2 was based on classification on sample plots in a systematic grid within stands. Variables related to soil depth and vegetation types were used for classification on each plot. Method 3 was based on a prediction of site quality on sample plots systematically distributed within stands. Plots where the site quality was predicted to be less than H40=5.0 meter, i.e. a potential yield capacity of less than 1.0 m3/ha/year inclusive bark, were classified as non-productive. Site quality was predicted by means of regression functions developed for the purpose of classification. Site properties as soil depth, soil type and vegetation type were used as independent variables. 72 blocks located in Southeast Norway were selected for the investigation. The blocks were subjectively located in stands with occurrences of rock on surface, shallow soils and productive areas within stands. Longitude, latitude, height above sea level, slope and conditions with respect to water penetration and soil type were recorded for each block. All blocks were covered by a systematic grid of points (1x2 meter). Soil depth and vegetation type were recorded for each point. Height, diameter and coordinates were recorded for all trees on each block. In addition the age was recorded for trees suitable for site quality classification. Based on the experiences from the field work, and on the considerations around different sources of errors, a systematic sample plot inventory within stands, with classifications on each plot (Method 2), is recommended. The sample plot size should be small, e.g. circles with radius 1 meter. The following recommendations are given for classifications on each plot;The sample plot should always be classified as non-productive if the portion of rock on surface is larger than 50%.The sample plot should as a rule be classified as non-productive if the mean soil depth is less than 10 cm. If mean soil depth on the plot is 7-10 cm, the following considerations should be performed; - Vaccinio-Pinetum boreale, Eu-Piceetum myrtilletosum or a richer vegetation type on the plot indicate productivity, - trees within a plot which are a natural part of the stand with respect to size and species indicate productivity, - small areas within a plot with large soil depth (larger than 30 cm) indicate productivity. If mean soil depth on the plot is 10-15 cm, the following considerations should be performed; - Barbilophozio-Pinetum lapponicae or Cladonio-Pinetum boreale on the plot indicate non-productivity. Pure subjective judgments of the portion of non-productive forest land in stands should also in the future be the main element in practical inventories. As early as at the stand delineation phase, however, one should try to eliminate those areas which obviously are non-productive. In this way the amount areas with subjective judgments are reduced. Estimation of the portion of non-productive areas by means of systematic plot inventories within stands should be used from time to time to calibrate the subjective judgments. This is particularly important in sites with occurrences of rock on surface and shallow soils within stands. The results of such sample plot inventories might also be useful as reference data when non-productive forest land is estimated by means of photo interpretation.