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.
1999
Abstract
No abstract has been registered
Authors
M. Lavoie Peder GjerdrumAbstract
The aim of this study has been to investigate the effects of high temperature drying on the equilibrium moisture content, to verify the presence of hysteresis and to screen the effects of high temperature on timber quality. Further, we wanted to utilise the laboratory kiln at Forestia Sokna in a pilot project, to learn more about the experimental possibilities connected to this equipment. The hypothesis was that the equilibrium moisture content will decrease as the drying temperature increase. Five series of twelve spruce wood samples each were prepared to verify this hypothesis: air-dried (green samples), moist samples for desorption and dry samples for adsorption for the ordinary-progressive (72 C) and for the high temperature kilns (115 C). The tension has been measured to compare the timber quality between ordinary-progressive and high temperature kilns. The conclusion is that there was too much stochastic noise to verify the initial hypothesis. Consequently it was impossible to confirm the presence of hysteresis. There are interesting observations to make in further research on how fast the equilibrium moisture content is reached according to the drying temperature. This experiment has been accomplished using Norway spruce, and further research should include Scots pine or other coniferous species.
Abstract
No abstract has been registered
Authors
Kari Anne SølvernesAbstract
The impact of climate change, i.e. elevated atmospheric CO2 and increased temperature, on a mini forest ecosystem was studied for three years in an open-top chamber experiment at s, Norway. Clones of Norway spruce (Picea abies L. Karst.) and one clone of Silver birch (Betula pendula Roth.) were grown in monolithic lysimeters containing undisturbed profiles of boreal forest soil. Seedlings and clones of Norway spruce were also grown in pots with fertilised peat. The atmospheric CO2 concentration was increased with 50 and 100 % of the present CO2 concentration, i.e. to approximately 500 and 700 mol mol-1 CO2. Ambient CO2 (380 mol mol-1 CO2) in chambers and at outside control plots (chamber control) were also included. There were two replicates of each treatment.The soil temperature was increased by 2 - 3 C. Growth and chemical composition of plants, leachates and soil chemistry were measured. Elevated CO2 caused a limited growth increase in Norway spruce and Silver birch. The CO2 effect was largest when the plants received good nutrient supply. The effect of CO2 on height increment was probably depended on growth pattern. When the plant exhibited free growth the stimulation of top shoot elongation was larger than when the plant exhibited predetermined growth. The benefit of elevated CO2 was also probably larger for Silver birch than for Norway spruce. The chemical composition of the plants were almost unaffected by elevated CO2. Increased soil temperature caused an increased mineralisation. Increased amounts of N and Al were released and leached from the soil. The data obtained from the leachates from the 500 mol mol-1 CO2 birch lysimeters during the two last growth seasons were surprisingly and not expected. In these leachates the pH and the concentrations of Al and TOC were increased in both replicates compare to the other treatment with birch. It was hypothesised this could be caused by increased exudations of organic compounds from Silver birch roots induced by elevated CO2
Authors
V. Koski Jouni Partanen H. Hänninen Egbert BeukerAbstract
No abstract has been registered
Authors
Tor-Gunnar Vagen Yibabe Tilahun Kjell EsserAbstract
No abstract has been registered
Authors
Per Holm NygaardAbstract
This thesis deals with effects of acidification, fertilisation and addition of Al on boreal vegetation as studied in different field- and laboratory experiments. The results are discussed in relation to the natural vegetation dynamics and critical loads of S and N for forest soils. Field experiments with artificial acid rain caused damage to bryophytes like Pleurozium schreberi and Dicranum polysetum at pH 2.5 and pH 3.0. The presence of Melampyrum pratense was reduced when treated with pH 2.5 and pH 3.0. For the pH 2.5 treatment, a decreased leaf production and decreased internal Mg concentration of Vaccinium myrtillus leaves were recorded. Treatment with pH 2.5 and 3.0 resulted in decreased base saturation in the O and E horizons, in particular Mg2, which may explain the effects on V. myrtillus. Repeated N-fertiliser additions caused vegetation changes, particularly at higher doses (1500 kg N/ha).An increase in cover of the species Deschampsia flexuosa, Molinia caerulea, Agrostis capillaris, Carex canescens, Rubus idaeus, Epilobum angustifolium and Dryopteris assimilis were found 8 years after the last N-application. Chemical analysis of leaves of V. myrtillus demonstrated an increase in N and a decrease in P concentrations on the fertilised plots compared to controls.The concentration of exchangeable Ca2, Mg2and K in the humus layer were reduced in fertilised plots compared to control plots. No differences in pH(H2O) or exchangeable acidity in the humus layer were found between fertilised plots and control plots. Laboratory experiments with Mg-limited Norway spruce seedlings showed that 80 M Al3 and a constant molar Ca/Al ratio of 0.2 decreased the uptake of Ca2 and Mg2, and reduced root length growth. However, no indication of an ameliorating effect of K on Al were seen, therefore these experiments give no support for including K into the critical load criterion. In the critical load calculation it seems that the molar Ca/Al ratio has been emphasised too much, and in particular that the scientific evidence of the critical chemical value (Ca/Al=1) is not well documented. A lot of the processes going on in the forest ecosystem are oversimplified or even left out in the present calculations. Long-term monitoring of forest vegetation at Karlshaugen, under moderate deposition regime of S and N, showed that other processes than deposition of S and N determine the vegetation dynamics, in particular the development of the dominant canopy species and field layer species seems to be much more important because of their influence on light and nutrients. Reduced frequency and persistence were shown for many field layer species and cryptogames during a 60 years period. A comparison of pH in soilwater from O-layer between 1961 and 1991 showed an increase in median pH of 0.1 pH unit for the area
Authors
Celine Rebours Chantal Billard Anne Marie Rusig Joel CossonAbstract
No abstract has been registered
Authors
O. Janne Kjønaas Anne Camilla Bergkvist Arne Olav StuanesAbstract
No abstract has been registered
Authors
Tonje Økland Rune Halvorsen Økland Eiliv SteinnesAbstract
No abstract has been registered