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
Erik Jautris Joner C. LeyvalAbstract
Phytoremediation as a means of cleaning up polluted soils has gained popularity during the last decade due to its convenience and low costs of installation and maintenance. When the target pollutant is biodegradable, this technology exploits the stimulating effect that roots have on microbial processes and physical/chemical modifications in the rhizosphere.Among the microorganisms that affect rhizosphere processes, symbiotic fungi forming mycorrhizas induce a series of changes in plant physiology, nutrient availability and microbial composition that may determine the outcome of a phytoremediation attempt. Beyond the rhizosphere, mycorrhizal hyphae act as the roots of the roots, and may thus extend the rhizosphere into the bulk soil by creating a new interface of soil-plant interactions: the hyphosphere.We here discuss some of the recent results on phytoremediation of organic pollutants with emphasis on processes in the mycorrhizosphere, and highlight future research priorities
Abstract
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.
Abstract
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.
Abstract
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.
Abstract
No abstract has been registered
Abstract
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.
Authors
Holger LangeAbstract
For the intepretation of multifractal properties of experimental time series, two prominent procedures used are the double trace method (DTM) and the universal multifractal (UM) approach. We calculated multifractal spectra for a collection of long-term precipitation, air temperature and river discharge records, covering a wide range of spatial scales.Considering K(q) in this framework leads to an effective classification of dynamical behavior. Comparison of the DTM and UM methodologies, however, reveals substantial differences which make them difficult to reconcile. This is in particular true for the discharge case.The scaling exponent is generally larger in magnitude for the DTM and in some cases even extends into the non-analytical regime. Part of previous work thus could not be confirmed. Whether the description of river flow as multifractal process is feasible remains an open question. http://www.cosis.net/abstracts/EAE03/05092/EAE03-J-05092.pdf
Abstract
No abstract has been registered
Authors
Erik Jautris Joner C. LeyvalAbstract
Phytoremediation of organic pollutants depends on plant-microbe interactions in the rhizosphere, but the extent and intensity of such rhizosphere effects are likely to decrease with increasing distance from the root surface.We conducted a time-course pot experiment to measure dissipation of polycyclic aromatic hydrocarbons (PAHs) in the rhizosphere of clover and ryegrass grown together on two industrially polluted soils (containing 0.4 and 2 g kg(-1) of 12 PAHs). The impact of the fungal root symbiosis arbuscular mycorrhiza (AM) on PAH degradation was also assessed, as these fungi have previously improved plant establishment on PAH-polluted soils and enhanced PAH degradation in spiked soil.The two soils behaved differently with respect to the time-course of PAH dissipation. The less polluted and more highly organic soil showed low initial PAH dissipation rates, with small positive effects of plants after 13 weeks. At the final harvest (26 weeks), the amounts of PAHs extracted from nonplanted pots were higher than the initial concentrations. In parallel planted pots, PAH concentrations decreased as a function of proximity to roots.The most polluted soil showed higher initial PAH dissipation (25% during 13 weeks), but at the final harvest PAH concentrations had increased to values between the initial concentration and those at 13 weeks. An effect of root proximity was observed for the last harvest only. The presence of mycorrhiza generally enhanced plant growth and favored growth of clover at the expense of ryegrass. Mycorrhiza enhanced PAH dissipation when plant effects were observed.
Authors
Lars Sandved Dalen J. Watkinson A.A. Sioson V. Singal D. Kumar N. Ramakrishnan L.S. Heath Carl Gunnar Fossdal R. GreneAbstract
Trees cover over one-third of the world\"s land area and carry out about two-thirds of global photosynthesis. Coniferous forests cover 1.2 billion hectares of Alaska, Canada, Scandinavia, and Russia, and comprise one-fourth of the world\"s boreal and temperate forests. More than 50% of Scandinavia\"s land area consists of forests, mostly coniferous. Information about the molecular responses in trees to biotic and abiotic factors is therefore of great importance - both scientifically and practically.Transcript regulation in response to drought stress was investigated for Norway spruce (Picea abies) with microarrays including 1,700 cDNAs from 5 EST libraries from Pinus taeda and analyzed using the Expresso Microarray Management System.In order to verify the level of drought stress, we measured the physiological status of the plants. After four days of drought, chlorophyll fluorescence was reduced by 6% and after eight days by over 40 %, compared to the control. Hybridizations of spruce RNA to microarray slides was used to probe for changes in transcripts from two to eight days after watering stopped.Monitoring of transcript levels was accomplished by hybridizing spruce cDNA to the 1700 element microarrays. After two days of drought, circa 2 % of the transcripts in Norway spruce were significantly upregulated and 7 % were downregulated. At the end of the experiment after eight days of drought needle chlorophyll fluorescence was reduced by 40 % compared to the control, and 6 % of the transcripts were upregulated and 12 % of the transcripts were downregulated. Results from inductive logic programming are also presented.