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.
2006
Abstract
No abstract has been registered
Authors
Ingerd Skow Hofgaard Leslie A Wanner Gunhild Hageskal Birgitte Henriksen Sonja Klemsdal Anne Marte TronsmoAbstract
No abstract has been registered
Authors
Kjersti Holt HanssenAbstract
An increasing interest for uneven-aged forestry requires more knowledge concerning the impact of selective cuttings on the physical environment, and the effect of an uneven-aged forest structure on establishment and growth of the regeneration. Our objectives were to correlate pre-harvest growth and vitality of advance seedlings and saplings with light levels in the stands, and to measure the change in light availability following selective cuttings. We performed a selective cutting with two levels of removal (40 and 60 % of standing volume) in three uneven-aged stands in eastern Norway, two Norway spruce (Picea abies) stands and one Scots pine (Pinus sylvestris) stand. The standing volumes in the spruce stands were approximately 300 m3 ha-1, in the pine stand 180 m3 ha-1. The selective cutting was aimed at removing the economically ripe trees, resulting in the removal of large as well as damaged and diseased trees. Light levels were measured with hemispherical photography before and after cutting, and sapling growth and vitality was registered. Spruce sapling vitality and growth before cutting varied with light conditions. Saplings with good vitality on average received 26 % of full daylight. Few pine saplings had good vitality even though the average light level in the pine stand was 35 %, illustrating the difference in shade tolerance between the two species. The relationship between light levels and sapling growth might be caused by the availability of both light and soil resources, as a large gap will offer a better supply of nutrients and water as well as light. The selective cutting increased average light levels with 10-30 percent points. In the spruce forests, the frequency distribution curve of measured light values was rather narrow and peaked before harvesting but wide and low afterwards (Fig. 1), indicating that the selective cutting created a broad range of site conditions below the canopy. For the pine forest, the light distribution curve kept a rather narrow, unimodal shape also after cutting.
Authors
Jørgen Aleksander Mølmann Olavi Junttila Øystein Johnsen Jorunn Elisabeth OlsenAbstract
No abstract has been registered
Abstract
Six cropping systems, ranging from conventional arable without livestock to organic livestock farming dominated by ley, have been compared in 1990 and 2004 in SE Norway. Ley in the crop rotation increased density and biomass of earthworms and channels in both organic and conventional systems. A ley proportion higher than 25 % only increased the density of channels. Among the arable systems, the organic system had a higher density and biomass of earthworms as compared to the conventional systems. Among the fodder systems, the optimised system had the highest density of earthworms in 2004, but there were no differences between these systems in earthworm biomass or density of earthworm channels.
Authors
Toril Drabløs EldhusetAbstract
No abstract has been registered
Authors
Toril Drabløs EldhusetAbstract
No abstract has been registered
Abstract
The life-cycle, overwintering stategy and control of Arion lusitanicus in Norway is documented and discussed.
Abstract
No abstract has been registered
Abstract
In a balanced experiment based on 20 field plots located in a 21 km(2) Scots pine forest in southeast Norway covering age classes from newly regenerated to old forest, leaf area index (LAI) was determined in field by a LAI-2000 instrument and hemispheric photography. Based on a fortualized framework, i.e., the so-called Beer-Lambert law, gap fraction derived from small-footprint airborne laser scanner data was regressed against field-measured LAI. LAI was strongly (R-2 =0.87-0.93), positively, and linearly related to the log-transformed inverse of the gap fraction derived from the laser scanner data. This was as expected according to the Beer-Lambert law, as was the absence of an intercept, producing a directly proportionality of the two variables. We estimated an extinction coefficient for the first return echoes to be 0.7, fortunately fairly stable across age classes, and this is likely to be a parameter specific for the applied laser scanner system under the given flight and system settings, such as flying altitude and laser pulse repetition frequency. It was demonstrated that airborne laser was able to detect defoliation in terms of estimated changes in LAI, by three repeated laser data acquisitions over the area where severe insect attacks were going on in between the acquisitions. (c) 2006 Elsevier Inc. All rights reserved.