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.
2003
Sammendrag
Modern information technology allows the investigation of the characteristic properties of living systems from a new perspective. Which of the ecosystem features are necessary conditions resulting from their constraints, which are accidental, constituting contingent facts of their respective histories?As long as we know of a single phylogenetic tree in nature, the difference is hard to tell, rendering the reconstruction and realisation of artificial ecologies a major challenge. It has been taken up by the high technology of the time since decades; since two decades, IT is leading in this respect.Are there life forms that can be created in contemporary computers, and which ones? Successes and failures of a number of virtualizations are forming de facto constraints for theoretical ecosystem research. Artificial Life (AL) research appears to be not just another attempt towards realistic models for ecological systems, but undermines the basic assumptions of most of conventional modeling in this area: in AL, behavior is in general irreducible to internal mechanisms; behavior results rather from interactive and intentional usage of the simulation.We try to elucidate and demonstrate the crucial role of interaction in these simulations, drawing from current developments in theoretical computer science as well as a number of examples. We propose a new classification of ecosystem models according to its degree of interactivity.
Forfattere
Ketil KohmannSammendrag
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Sammendrag
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Forfattere
Kjell AndreassenSammendrag
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Sammendrag
In this study of 130 sites with different management we investigated whether vascular plant species richness is significantly reduced when traditionally managed hay meadows are abandoned and reforested. We also compared the effects of reforestation with those of intensified land-use to see which have the largest effects on species richness. Finally, we investigated the relative importance of relevant ecological factors for species richness.While the use of artificial fertilizers in traditionally managed hay meadows has resulted in significantly lower species richness, and intensive cultivation in even lower species richness, abandonment with reforestation has not decreased the species richness significantly.Productivity and habitat diversity have determined the species richness of meadows on the scale (0.035.1 ha) of this study. Low productivity is a prerequisite for high species richness in meadows. Maximum species richness was observed in unproductive, old, traditionally managed hay meadows with a high soil pH and high habitat diversity. The high species richness of these meadows suggests that they are in urgent need of conservation.
Sammendrag
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Sammendrag
We studied four south-facing and three north-facing boreal spruce forest stands (ca. 0.1ha each) in SE Norway with the aim of testing the hypothesis that former logging has long-term effects on boreal forest-floor vegetation. The stand series comprised unlogged natural forests and forests that were selectively or clear cut 6070 years prior to our study. Each stand was described with respect to history of forestry impact and tree-stand structure.Environmental, species number, species abundance and species composition (vegetation gradients obtained as ordination axes) variables obtained for 25 m1m plots in each stand were tested for among-stand differences. Significant among-stand differences were found, partly related to former forest management and partly due to among-stand differences in topography.Differences among stands related to management were found for tree stand density, highest in managed stands, and for Dryopteris expansa agg. and Luzula pilosa abundances, peaking in formerly clear-cut stands. Species number (at plot or stand scales) was weakly related to former management.On southerly as well as northerly aspects, gradients in species composition were found that separated plots according to former management. Differences among stand conditioned on topography resulted in opposite patterns in the two series of stands because among southerly stands the clear cut was the least while among northerly the clear cut was the most strongly sloping. Low-inclination sites tended more strongly to be paludified and to have high Sphagnum cover, and to have low abundance of specific microsites with small mosses and hepatics. Vegetation gradients related to soil moisture and microtopography were found for both aspects.A strong gradient in species composition related to tree influence at within-stand scales was found, with variation in species number. Existence of such a gradient should provide for significant biotic effects (of short or long duration) of the environmental changes that take place during forest re-growth: (1) the immediate creation of small or large tree-layer gaps by tree felling; and (2) the closing of the tree layer during the regeneration phase.Most notably, the phases at which the tree layer reaches minimum and maximum cover, respectively, may act as `bottlenecks\" for survival of forest-floor species. We conclude that forestry impacts understorey vegetation by way of changes in tree-layer structure and, to a lesser extent, substrate availability and the local environment, during forest regrowth. The extent and duration of this impact will depend on a complex set of factors.Our results are consistent with the view that if maintenance of species diversity is aimed at, environmental considerations should be built into forest management practices, preferably by mimicking the natural structural dynamics of the tree layer.
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Sammendrag
Spatio-temporal analyses of non-epidemic bark beetle populations may provide insight in dynamics predisposing for outbreaks. The present article presents a spatio-temporal analysis of the population dynamics of Ips typographus based on pheromone trap data from southeast and mid-Norway in the post-epidemic period 19792002. The analyses include regression analyses, hierarchical cluster analysis, and analysis of spatial synchrony of beetle time series and climatic data by means of nonparametric spatial covariance functions. The mean abundance of beetles declined linearly with latitude. In addition, the time series means were higher in areas with high forest productivity and rocky soils predisposed to drought. The time series patterns differed significantly between northern and southern study areas. The regional synchrony of the time series was fairly high (0.38), indicating that some large-scale climatic factor may influence the dynamics. Windfelling was the external variable showing the most parallel pattern of correlation to the beetle dynamics. We thus posit that large windfall events may be a major instigator and synchronizer of beetle outbreaks in areas subjected to regionalized weather systems.
Forfattere
Anders LunnanSammendrag
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