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
Authors
Svein SolbergAbstract
No abstract has been registered
Authors
P.K. Egeberg Morten Eikenes E.T. GjessingAbstract
In Norwegian lakes, organic nitrogen typically constitutes about 60% of the total dissolved pool of nitrogen. However, evaluation of its effect on aquatic ecosystems and its role as promoter of heterotrophic growth in water distribution systems is difficult because of restricted knowledge about the various forms of organically-bound nitrogen in water. On line standard wet chemical analysis of total nitrogen was combined with high-performance size exclusion chromatographic (HPSEC) separation of natural organic matter (NOM) for investigation of the distribution of nitrogen between size classes of NOM. It was found that the high molecular weight (HMW) size fractions (humic acids) are enriched in nitrogen relative to the low molecular weight (LMW) size fractions (fulvic acids, nominal molecular weights of about 1000 Daltons) by a factor of up to 10. The low molecular weight size fractions (a few hundred Daltons) are interpreted to be of autocthonous origin based on their low C/N ratios, and correlation with the eutrophic status of the source waters. It was observed that NOM from water sources surrounded by large catchments contains relatively more nitrogen in HMW size fractions than NOM from small catchments, except that bog-derived NOM is particularly enriched in HMW nitrogen.
Abstract
Studies were undertaken in forest ecosystems of the northwestern Kola Peninsula, Russia and South-Varanger, Norway in the zone affected by the Pechenganikel smelter. The soils consist mainly of shallow sandy iron-humus-illuvial and iron-illuvial podzols on highly bouldery unsorted morainic deposits of course texture, fluvioglacial sands and bedrocks.Plant specimens were collected from 16 plots located at different distances from the source of emissions: Pinus sylvestris needles, bark and wood, dwarf shrub (Empetrum hermaphroditum, Vaccinium myrtillus and Vaccinium vitis-idaea ) leaves, wavy-hair grass (Deschampsia flexuosa), green mosses (Hylocomium splendens and Pleurozium schreberi) and lichens (Cladina rangifirina [Cladonia rangiferina], and Cladina stellaris [Physcia stellaris]) were collected at the end of the growing season.Results showed that the elemental composition of the dominants of the tree, grass-shrub, and moss layers was affected by the sulfur and heavy metals from the source of pollution. The content of nickel and copper in pine needles near the smelter exceeded control levels by an order of magnitude and the content of sulfur exceeded it twofold, reaching toxic levels.In addition to the direct input of pollutants from the atmosphere, soil contamination by nickel and copper within a 30 km radius of the smelter will have adverse effects on mineral nutrition of plants.It is concluded that the disturbance of biological cycles because of the active involvement of pollutants and the decreased availability of nutrients results in retardation of plant growth, a reduction in forest biomass and alterations in plant succession and species composition that leads to simplification and death of forest ecosystems.
Abstract
This study describes how crown density changes were distributed within monitoring plots, in order to determine whether the reduced crown density observed could be explained as a worsening of a limited number of unhealthy or small and slightly suppressed trees.Crown density, yellowing, coning and stem diameter data were available from 447 selected plots comprising 22560 single trees all having a complete 1990-97 series of crown condition data.The eight years series of crown density for each tree were recalculated to two median values, for 1990-93 and 1994-97, in order to reduce the influence from short time variations including random errors. The scores for yellowing and amounts of cones were averaged over the years 1990-93. These variables, and diameter, were recalculated to rank indices within each plot.Relationships between variables were described by graphs and examined by correlation analyses of the indices. The trees tended to retain their internal ranking. Generally, when crown density for a plot has changed, most of the trees were affected. The most defoliated trees in each plots had the least negative changes, but except from that the trees were equally affected regardless of their yellowing, amount of cones, and their size.The results demonstrates that any effects from competition between the trees were sufficiently removed in the assessments, even in densely stocked stands.
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
J. Pomeroy R. Granger A. Pietroniro J. Elliott B. Toth N. HedstromAbstract
No abstract has been registered
Authors
A. PliuraAbstract
No abstract has been registered
Authors
Tor MykingAbstract
Winter dormancy reduces or inhibits totally the growth ability of buds. Dormancy release and budburst in Scandinavian Betula pendula Roth. and B. pubescens Ehrh. ecotypes were studied in controlled environments. There was a gradual decline in the heat-sum requirement for budburst with increasing chilling time. Two main clines in time of dormancy release appeared in ecotypes of different geographic origin, a latitudinal cline and a coastal-inland cline in which the duration of dormancy increased southwards and towards the coast. In addition, dormancy was later alleviated in high-altitude than in lowland B. pubescens ecotypes. In late autumn, after 44 chilling days, time to budburst at 15C was less in plants chilled at 0C than in plants chilled at 10C, indicating that 0C was most effective for dormancy release. In January, after 105 chilling days, however, dormancy release was completed, and budburst was earliest in plants chilled at 10C. At this stage there were no detectable differences in effectiveness between fluctuating and corresponding constant temperatures (6 to 21C) in promoting growth and budburst in B. pubescens. Long photoperiods significantly reduced time to budburst in partly dormant buds, but had no effect when dormancy was fully released
Authors
Oddvar SkreAbstract
The biomass in four dominant field layer species was followed during six years after a fire in a pine forest in Sveio, western Norway. The overall biomass in the different species was estimated from the biomass per shoot, the shoot densities in pure stands of the investigated species and the percentage cover at medium burned sites. Corresponding measurements were made at control plots outside the burned area.The method was checked by comparing with ordinary area based sampling technique, and a general good agreement was found. The Vaccinium species and calluna were the dominant species at the control plot.Three years after the fire the total overall biomass at the burned site was already higher than at the control site, due to improved light and nutrient conditions. A strong increase in the overall biomass of Calluna vulgaris and deschampsia flexuosa was found in burned areas, and a slower regrowth of Vaccinium myrtillus and V. vitis-idaea.However, in the future the biomass is expected to decrease, and the species composition will probably change as nutrients are leached out of the soil and pine and deciduous trees (Betula pubescens and Salix caprea) are regerating from seeds and roots, leading to increased competition in the field and shrub layer.
Authors
Albert WinsentsAbstract
Describes results of a comparison of logging with running skylines on low bearing capacity terrain and typical skyline terrain in Norway. Study addresses technical issues of the same growing concern to minimize logging impact on sensitive terrain. Study also describes use of running skylines over special intermediate supports. Future research needs for mobile tailholds and supports, plus mechanized harvesting opportunities are suggested.