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.
2009
Abstract
In this study, we surveyed the long term effects of liming and fertilizing in old Scots pine stands on the ectomycorrhiza (ECM) colonization, tree growth and needle nutrient concentration 35 years later. Four mature stands of Scots pine on low productive mineral soil were limed in 1959 and 1964 with total doses of limestone ranging from 3 to 15 Mg ha1 and fertilized with nitrogen (N) in 1970. Thirty-five years after the first liming treatment, all stands were analysed for tree growth and needle nutrient concentrations and two of the stands were also analysed for ECM colonization. ECM colonization increased significantly with liming from 61.5% in the control plots to 88% in the plot with the highest limestone dose...
Abstract
No abstract has been registered
Abstract
The soil is considered to be the major Carbon (C) sink in boreal forests, thus determination of soil carbon fluxes is essential for reliable C budgets. Especially partitioning of soil and root respiration is a major challenge. Soil respiration (Rs) consists of autotrophic respiration (Ra, respiration of plant roots and of microorganisms living on root-derived organic C in the rhizosphere) and heterotrophic respiration (Rh, respiration of free-living microorganisms during their decomposition of soil organic matter. In our study we attempted to estimate the contribution of roots to soil respiration by a girdling experiment. The study was established in two Norway spruce (Picea abies) stands, 35 and 65 year old, at Nordmoen, southeast Norway. Four quadratic plots (21m x 21m) were chosen within each of the two stands in spring 2006 and within two plots all trees were girdled. To estimate the contribution of root respiration, we measured CO2 efflux within each plot with a PP EGM-4 gas monitor for CO2, at permanently marked spots during two years (2006 and 2007). In the youngest stand in 2006, Rs in the control plots was higher than in the girdled plots at all measurement occasions. During this period, the mean Rs in the girdled plots was 64.9 % of the mean Rs in the control plots. In 2007, the Rs was highest in the girdled plots on most occasions, but the difference was never significant. In the oldest stand, Rs was also highest in the control plots in 2006 and highest in the girdled stand in most cases in 2007, but the difference was never significant. The implications will be discussed.
Abstract
No abstract has been registered
Abstract
Tree and understorey fine root growth and longevity was determined by minirhizotrone research in northern Finland. The study was made in a 70-year-old Norway spruce stand, growing on a mesic mineral soil site in the Kivalo experimental forest. Three replicate plots were established, and three vertical minirhizotron tubes installed in June 2003 in soil of each of the three plots. The images were taken at monthly intervals (altogether 11 sessions) during the growing seasons 2004, 2005 and 2006. The lengths, diameters and status (new, living, dead, disappeared) of Norway spruce and understorey (mainly shrub) fine roots were recorded. Our data indicates that there were more new roots growing in the upper soil depths (the organic layer) than in the lower soil depths (mineral soil). Roots in the organic layer, however, elongated less than roots in the upper mineral soil. The growth rate was highest in late summer and early autumn. Regarding root longevity, both trees and understorey showed the same trends by root order and soil depth; the average longevity was 14-16 months. The time from death to disappearance was 6-8 months for trees and 2-7 months for understorey. Furthermore, monthly trends of new roots born versus their death and/or disappearance by soil depth are also presented.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Introduction: Current risk assessment procedures for contaminated land and for pesticides often fail to properly characterize the risk of chemicals for environment or human health and provide only a rough estimate of the potential risk of chemicals. Chemicals often occur in mixtures in the environment, while regulatory agencies often use a chemical-by-chemical approach, focusing on a single media, a single source, and a single toxic endpoint. Current concepts to estimate biological effects of chemical mixtures mainly rely on data available for single chemicals, disregarding interaction between chemicals in soils. The importance of soil microbes and their activity in the functioning of soils impose a need to include microorganisms in soil quality assessments (Winding et al., 2005) including terrestrial ecotoxicological studies. Numerous papers have been published on the effects of different contaminants on soil microbes, establishing changes in soil microbial diversity as an indicator of soil pollution, but only a limited number of molecular studies investigating fungal diversity in the environment have been performed. The main objective of the study presented here, is to assess the applicability of changes in soil microbial diversity and activity levels as indicators of ecologically relevant effects of chemicals contamination. We have studied the effects of the fungicide picoxystrobin and the chemical 4-n-nonylphenol, on the microbial biodiversity in a Norwegian sandy loam with focus both on prokaryotes and the fungal species. 4-n-nonylphenol is a chemical occurring in high amounts in sewage sludge, hence, these chemicals may occur as single chemicals as well as in mixtures in soils. This work is part of the research project ‘Bioavailability and biological effects of chemicals - Novel tools in risk assessment of mixtures in agricultural and contaminated soils" funded by the Norwegian research council.Methods: Soil samples were treated with the single chemicals or mixtures and incubated at 20°C. Continuous monitoring of respiration activity as well as occasional destructive sampling for extraction of soil DNA, RNA, and chemical residues was performed through a 70 d period. Amplification of soil bacterial and fungal DNA was followed by T-RFLP analysis to assess chemicals effects on soil microbial diversity. Further work will include analyses of extracted soil RNA to assess chemicals effects on important soil functions (e.g. nitrogen cycling, decomposition of organic matter) and an assessment of chemicals effects on the genetic diversity of the soil by high throughput shot-gun sequencing. Finally the results will be evaluated to assess the suitability of any specific group, species or activity/function as biomarker for the selected chemicals (and possibly their group of chemicals).Results and conclusions: A project outline and preliminary results from the project will be presented at the conference.ReferencesWinding A, Hund-Rinke K, Rutgers M (2005). The use of microorganisms in ecological soil classification and assessment concepts. Ecotoxicology and Environmental Safety 62: 230-248.
Abstract
In this study we aimed at understanding the mechanisms that affects an epidemic development of Neozygites floridana in a Tetranychus urticae population. This was done by comparing how many spores a cadaver infected with a N. floridana isolate could produce and at what distance and in which directions they could be thrown on a coverslip at temperatures relevant to the northern hemisphere (13, 18 and 23oC). The highest number of spores were produced at 13oC at a number of 1886. Numbers of spores thrown at 18oC and 23oC were 1733 and 1302 respectively. Temperature had a significant effect on sporulation. Most of the spores were thrown at a distance of 0-0.6 mm from the cadaver. Cadavers placed on the underside of a coverslip were able to throw spores back up on the coverslip surface. A whole plant bioassay was also conducted to reveal where on a plant T. urticae infected with N. floridana die and sporulate. Cadavers showed a different verical distribution on the cucumber plant compared to healthy spider mites. Most of the cadavers were located at the lower to the middle part of the plant, while healthy spider mites were more evenly distributed on the whole plant.
Abstract
Neozygites floridana is a fungus in the order Entomophthorales that is a natural enemy of several spider mite species including the two-spotted spider mite, Tetranychus urticae. When conditions are right, this fungus may cause epizootics in spider mite populations and kill high numbers of mites. The fungus is therefore promising for biological control of T. urticae in strawberry and can be used in combination with other pest management strategies. Our previous studies have shown that N. floridana is compatible with other biocontrol methods such as predatory mites. Phytoseiulus longipes fed on fungus-infected T. urticae laid equal number of eggs to those fed on healthy prey. This indicates that the fungus does not affect this predatory mite negatively. In a choice experiment (hosts with and without N. floridana), P. longipes fed indiscriminately irrespective of the presence of the fungus. The compatibility of biological control methods with pesticides is of great importance for an integrated pest management system to work well. Some acaricides and fungicides have the potential to affect both beneficial fungi and predatory mites and careful selection of pesticides that are not harmful to these beneficial organisms can promote their biocontrol potential. Our studies have shown that the fungicides captan, mancozeb, tolylfluanid, fenhexamid, cyprodinil + fludioxonil affect N. floridana in a way that may be detrimental to the biocontrol potential of this beneficial fungus in the field. Use of resistant varieties is also important in integrated pest management because pests are known to be more vulnerable to pathogens if they feed on poor or resistant plants and our studies on effects of host plants of spider mites confirms this.