Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
1999
Authors
Tonje Økland Rune Halvorsen Økland Eiliv SteinnesAbstract
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Authors
Tore SkrøppaAbstract
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Authors
Lennart Eriksson Klas ÖsterbergAbstract
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Authors
Rune Halvorsen Økland Knut Rydgren Tonje ØklandAbstract
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Abstract
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Authors
Arnt Kristian Gjertsen Svein Ola MoumAbstract
The paper describes an operational method for automatic map generalisation. Operational methods are often pragmatic in nature and only works well in special cases. General methods need to be founded on solid knowledge based on understanding of the map generalisation process as performed by expert cartographers. Today, much research in the area is concentrated on knowledge-based systems, and the research is directed on formalising generalisation knowledge. NIJOS has developed a pragmatic map generalisation method to generalise land-type maps from working scale 1:5000 to a working scale in the range 1:100.000–1:300.000. The method involves both attribute and geometric generalisation. The former was simple to implement in a database query language; the latter was more complex. A method based on deviding classes into separate thematic layers followed by a series of expansion and shrinkage operations was developed. The separate layers were later combined in a predefined and prioritised order. Important control factors were minimum area and minimum width. Both the size and the display time were greatly reduced. The method was successful in removing small areas, however, it was not 100% successful in removing narrow bridges and gaps.
Authors
Svein Solberg Knut Breivik Nicholas Clarke Tone Groeggen Ingvald Røsberg Kjetil Tørseth Dan Aamlid Wenche AasAbstract
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Abstract
The area along the Norwegian-Russian border is threatened by air pollution from emission sources on the Kola Peninsula. A permanent network of 78 systematically chosen monitoring sites has been established in eastern Finnmark, Norway. Species abundance data from the ground vegetation have been recorded from 1320 systematically chosen permanent plots inside 66 of these sites, using frequency in subplots and visual estimates of percentage cover. Environmental variables were obtained for the whole site. Multivariate data analysis has been used to describe the variation in the species composition and to study its relation to environmental variables and pollution impact. The analyses show that much of the variation in the species composition, based on average species abundance at the sites, is well explained by different soil and climatic conditions. However, estimated SO2 deposition, Ni, and Cu in the soil, and Ni in Cladina tissue have also been found to be statistically significantly correlated with the variation in the species data, but they explain only a minor part of the variation. The pollution impact over several years may have lead to a reduced lichen cover in the bottom-layer vegetation. Further development in an either negative or positive direction can be detected by re-investigations of the monitoring sites.
Abstract
This study aims to evaluate the quality of crown density data, based on independent, pairwise tree assessments. The data originates from monitoring of forest health (crown condition) in Norway; 250 plots, comprising 12 000 individual trees of Norway spruc e, have been reassessed by a single observer during 1990-95. Of the trees, 2300 were controlled more than twice, providing the possibility of evaluating the quality of assessed temporal changes of crown density. True errors (standard deviation) are estima ted to be about 10% for single trees and 5% for plot means, while the real standard deviation of the differences were slightly higher. The errors of the temporal changes of crown density were of similar magnitude. Systematic differences in crown density w ere found between sites and plot types, partly resulting from observer bias. However, the results suggest that observer bias is really the result of each observer\"s personal style in assessment.
Abstract
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