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.
1998
Abstract
Change in crown density for Norway spruce (Picea abies) from 1988 to 1993 in three independent forest monitoring projects in southern Norway were compared. An increase in crown density was found in a countywide systematic random sample, whie measurements taken in old-growth forests reported a decline. These contradictory results may be due to: (1) high sensitivity of high-elevation forests to various kinds of environmental impact; (2) differences in stand age and management practice; and (3) different sensitivity to long distance airborne pollutants. The systematic random sample encompassed stans of several age classes from two counties, while the two other studies were restricted to old-growth forest in two smaller are as. A possibe explanation of the differences is thus that the three studies refer to differet popuations as a resut of different sampling strategies.
Authors
Geir-Harald Strand Tonje Økland Rune Halvorsen ØklandAbstract
Change in crown density for Norway spruce (Picea abies (L.) Karst.) from 1988 to 1993 in three independent forest monitoring projects in southern Norway were compared. An increase in crown density was found in countrywide systematic random sample, while measurements taken in old-growth forests reported a decline. These contradictory results may be due to (1) high sensitivity of high-elevation forests to various kinds of environmental impact; (2) differences in stand-age and management practice; and (3) different densitivity to long distance airborne pollutants. The systematic random sample encompassed stand of several age classes from two counties, while the two other studies were restricted to old-growth forest in two smaller areas. A possible explanation of the differences is thus that the three studies refer to different populations as a result of different sampling strategies.
Authors
Tore SkrøppaAbstract
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Dag FjeldAbstract
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Authors
Sondre Skatter Olav Albert Høibø Peder GjerdrumAbstract
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Authors
Arne Olav Stuanes O. Janne KjønaasAbstract
Nitrogen has been added to a forested 0.52 ha headwater catchment (G2 NITREX) at Grdsjn, Sweden, to study the ecosystem response to elevated N deposition. The catchment is dominated by naturally regenerated, mixed-age conifers, mainly Norway spruce, with Scots pine dominating in dry areas. After a pre-treatment period of about 1 yr of soil solution sampling, N was added to the whole catchment as an NH4NO3 solution by means of sprinklers. Total N input as throughfall to the catchment increased from the ambient 13 kg N ha-1 yr-1 in the pre-treatment year to a total of about 50 kg N ha-1 yr-1 in the 4 treatment years. Soil solution was collected by tension lysimeters at 4 locations in G2 NITREX covering a moisture gradient from the dry upper to the lower wet parts of the catchment, at 2 locations in a nearby control catchment (F1 CONTROL), and at 2 locations in an adjacent catchment (G1 ROOF) at which ambient throughfall is excluded by a roof and replaced by unpolluted throughfall added by sprinklers. After 4 yr of N addition, the volume-weighted average NO3 concentrations in G2 NITREX were higher than the pre-treatment values. Concentrations showed a progressive increase over time. In the 2 first treatment years this increase occurred only in the rooting zone but during the second 2 treatment years a pronounced increase also came in deeper layers. The lack of these trends in the F1 CONTROL and G1 ROOF catchments precludes natural variations in climatic conditions as the main cause for this increase. Relative to inputs, NO3 concentrations in soil solution were low and showed large variations between the drier and wetter locations with peak concentrations in late fall and spring. Nitrate in soil solution generally constitutes less than 10% of the inorganic mobile anions and thereby contributes much less to the leaching of H, Al, and base cations than CI and SO4, the dominant mobile anions. Soil solution NH4 has not changed relative to the control and roof catchments. However, the system is changing. Increases in NO3 leaching indicate reduced immobilization of NO3 that can be due to episodic excess N supply of the microflora together with episodes of high waterflow.
Authors
Vincent R. Franceschi Trygve Krekling Alan A. Berryman Erik ChristiansenAbstract
The bark anatomy of Norway spruce clones that were resistant or susceptible to Ceratocystis polonica, a bark beetle vectored fungal pathogen, was compared. The major difference concerned the axial parenchyma cells, called polyphenolic parenchyma (PP cells) because of their vacuolar deposits. The phenolic nature of the deposits was indicated by autofluorescence under blue light, and immunocytochemical studies demonstrating PP cells are enriched in phenylalanine ammonia lyase (EC 4.3.1.5), a key enzyme in phenolic synthesis. Susceptible clone PP cells occurred as single rows filled with dense deposits. The resistant clone had 40% more PP cells, which occurred in rows two cells thick with individual cells also scattered among the sieve cells, and had lighter deposits. Trees inoculated with fungus were analyzed but a distinct fungal response could not be separated from the general wound response. In the resistant clone, phenolic bodies were reduced in size and density or disappeared completely 12 day after wounding, and PP cell size increased. The susceptible clone phenolics and cell size changed only slightly. These data show that PP cells are active in synthesis, storage, and modification of phenolics in response to wounding, providing a primary site of constitutive and inducible defenses.
Authors
Anne Sverdrup-Thygeson Fred MidtgaardAbstract
No abstract has been registered