Hopp til hovedinnholdet

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

Scots pine (Pinus silvestris) logs and 106 Norway spruce (Picea abies) logs. Two of the models were the classical 3-parametric circle model and the 5-parametric ellipse model. These models were compared to the third model, the Fourier coefficient model, which had a variable number of parameters. By increasing the number of parameters in the Fourier coefficient model, this model fits the true shape perfectly. With the same number of parameters the Fourier model performed approximately as good as the two other models. To get a substantial improvement over the ellipse model the number of parameters had to be raised dramatically.

Abstract

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.