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.
2003
Authors
Tore SkrøppaAbstract
No abstract has been registered
Authors
Erlend Ystrøm Haartveit Dag FjeldAbstract
No abstract has been registered
Abstract
We fogged trees in two pine dominated forests in Norway with a synthetic pyrethroid in order to compare the canopy-dwelling fauna of arthropods between costal (Kvam) and boreal (Sigdal) sites and between old (250-330 years) and mature (60-120 years) trees at Sigdal. Almost 30,000 specimens were assigned to 510 species; only 93 species were present at both sites. Species diversity, as established by rarefaction, was similar in old and mature trees. However, the number of species new to Norway (including nine species new to science) was significantly higher in the old trees. We suggest that the scarcity of old trees, habitat heterogeneity and structural differences between old and mature trees may explain these patterns. Productivity and topographic position at the site of growth explained the between-tree variation in species occurrence for the more abundant species, which were mainly Collembola and Oribatida. Species diversity was similar at the boreal and coastal sites, but there were clear differences in species composition
Abstract
No abstract has been registered
Authors
Trond Knapp Haraldsen Per Anker PedersenAbstract
No abstract has been registered
Authors
Rolf Arnt Olsen Grete RasmussenAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Tron Eid Bernt-Håvard ØyenAbstract
Models for predicting mortality in even-aged stands were developed. The models rely on data from the Norwegian National Forest Inventory, and were designed for use in large-scale forestry scenario models. A two-step modelling strategy was applied: i) logistic regression models predicting the probability of complete survival to occur, and ii) multiplicative regression models for stem number reduction and diameter calibration. A joint model for all species predicting the probability of survival to occur on a plot was developed. Separate models for spruce, pine and broadleaved-dominated forests were developed for stem number reduction, while no appropriate models for diameter calibration were found. The phenomenon mortality is a stochastic, rare and irregular event, and this was reflected as low R2 in the models. However, the model performance appeared logical and the results of validations based on independent data were reasonably good, i.e. the presented models may be applied for large-scale forestry scenario analyses. With new rotations of permanent sample plot measurements, the models should be evaluated and, if necessary, revised.
Authors
Helge Lundekvam Eirik Romstad Lillian ØygardenAbstract
Norwegian agriculture depends heavily on governmental subsidies, due to small farming units and high costs. Due to a limited home market, many agricultural productions are also quantum regulated. Milk and grain production was regulated starting in the 1950 using region specific prices. At the level of three counties in south-eastern Norway, this policy resulted in an increase in the grain producing area from 30 to 80% of total agricultural area causing a similar reduction in grassland area over a'30 year period. The change in land use caused by this policy more than doubled the estimated soil losses by water erosion. During the late; seventies extensive land levelling in the same region stimulated by subsidies lead to an estimated two-three fold increase in soil erosion. The increase was especially high when former ravine landscapes used for pasture were levelled and turned into arable land that was ploughed in autumn. Very visible erosion and increasing negative offsite effects on water quality together with overproduction put an end to the subsidies for land levelling. Erosion research was started around 1980 and the results from this research lead to the introduction of several kinds of payments in the early 1990 to encourage more sustainable agricultural production. Since the policy changed there has been changes in cultivating systems and a reduction in soil erosion has been estimated. Thus, farmers' behaviour and soil erosion in Norway is strongly influenced by agricultural and environmental policy.
Authors
Knut Rydgren Rune H. Økland Tonje ØklandAbstract
No abstract has been registered