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
Authors
Dag FjeldAbstract
No abstract has been registered
Authors
Sondre Skatter Olav Albert Høibø Peder GjerdrumAbstract
No abstract has been registered
Abstract
No abstract has been registered
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
Authors
Sondre Skatter Bohumil KuceraAbstract
A new theory is presented on the cause of the prevalent directions of the spiral grain patterns found in conifers. The hypothesis is based upon the assumption that spiral grain has a function, i.e. that it represents a growth strategy to ensure survival of the trees. The mechanical function of the tree trunk is placed in focus, that is the ability of the trees to withstand external mechanical loads, mainly from wind. Spiral grain is an optimized growth feature when the trees are exposed to combined bending and torsion. Torsion occurs when the crown is asymmetric in the plane perpendicular to the wind direction. Systematic crown asymmetry, with heavier crowns on the south side, was confirmed by measuring the crown projections on 253 sparsely grown pines; 76.7% of the trees had longer branches on the south than on the north side, and the average length difference was 40.8 cm. By studying wind maps it was seen that most of the coniferous forests have prevailing westerly winds, which, when combined with the crown asymmetry, leads to a prevailing torque. Right-handed spiral grain in the outermost layers of mature trees is proposed to be a strategy to withstand this torque, i.e. to avoid stem breakage
Abstract
The seasonal variations in volume of the milk in Norwegian goat dairyfarming, complicate production of brand goat cheeses. In the specialised goat dairy farming system most kids are culled shortly after birth without utilising the meat. In this paper the farm economics of an alternative system with altered period of kidding (currently in theperiod from January to March) combined with production of meat and cashmere fibre, is examined. May kidding combined with raising the kids for 8 or 20 months yielded the m ost promising economical return. Raising the kids one year is also profitable when kidding takes place in February while December kidding seems to perform best with thepresent system of culling the kids right after birth. Cashmere fibre production seems to be profitable on Norwegian dairy goat farms and fibre and meat could become an optio n in countries seeking to improve incomes on dairy goat farms. Compared to the present system the changes also would be favourable from an animal welfare point of view.
Authors
Albert Tietema Bridget A. Emmett Per Gundersen O. Janne Kjønaas Chris J. KoopmansAbstract
As part of four European ecosystem manipulation experiments in coniferous forests, field-scale 15N tracer experiments have been carried out. The experiments involved a year-long addition of 15NH4 and/or 15NO3- to throughfall at experimental plots with different N inputs. The fate of this applied 15N in the important ecosystems pools (trees, ground vegetation, forest floor and mineral soil), as well as in drainage was measured. About 10-30% of added 15N was taken up by the trees and 10-15% was retained in the mineral soil. Both retention efficiencies were found to be constant with N input. The part of 15N retained in the organic layer was relatively high (20-45% of applied) at low N inputs (0-30 kg N ha-1 yr-1) but low (10-20%) at high N inputs (30-80 kg N ha-1 yr-1). An inverse relationship between N input and the loss of 15N in drainage was found: drainage losses increased as a function of N input. These results suggest that increased N inputs exceed the capacity of the microbial population to retain throughfall-N in the organic layer, with the result that N leaching increases.
Abstract
The genus Bryomyia comprises altogether eight species in the Palearctic region, including one new species Bryomyia amurensis Mamaev et Økland described in the present article. A revised key to the species of Bryomyia in the Holarctic region is presented.