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.
2011
Authors
Kyrre Linné Kausrud Jean-Claude Grégoire Olav Skarpaas Nadir Erbilgin Marius Gilbert Bjørn Økland Nils Christian StensethAbstract
Bark beetles (Coleoptera: Curculionidae, Scolytinae) feed and breed in dead or severely weakened host trees. When their population densities are high, some species aggregate on healthy host trees so that their defences may be exhausted and the inner bark successfully colonized, killing the tree in the process. Here we investigate under what conditions participating with unrelated conspecifics in risky mass attacks on living trees is an adaptive strategy, and what this can tell us about bark beetle outbreak dynamics. We find that the outcome of individual host selection may deviate from the ideal free distribution in a way that facilitates the emergence of tree-killing (aggressive) behavior, and that any heritability on traits governing aggressiveness seems likely to exist in a state of flux or cycles consistent with variability observed in natural populations. This may have implications for how economically and ecologically important species respond to environmental changes in climate and landscape (forest) structure. The population dynamics emerging from individual behavior are complex, capable of switching between “endemic” and “epidemic” regimes spontaneously or following changes in host availability or resistance. Model predictions are compared to empirical observations, and we identify some factors determining the occurrence and self-limitation of epidemics.
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Lars Olav Brandsæter Anne Kjersti Bakken Kjell Mangerud Hugh Riley Ragnar Eltun Haldor FykseAbstract
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Maria Björkman Ingeborg Klingen ANE Birch Atle M. Bones Toby Bruce Tor J. Johansen Richard Meadow Jørgen A.B. Mølmann Randi Seljåsen Lesley Smart Derek StewartAbstract
In this review, we provide an overview of the role of glucosinolates and other phytochemical compounds present in the Brassicaceae in relation to plant protection and human health. Current knowledge of the factors that influence phytochemical content and profile in the Brassicaceae is also summarized and multi-factorial approaches are briefly discussed. Variation in agronomic conditions (plant species, cultivar, developmental stage, plant organ, plant competition, fertilization, pH), season, climatic factors, water availability, light (intensity, quality, duration) and CO2 are known to significantly affect content and profile of phytochemicals. Phytochemicals such as the glucosinolates and leaf surface waxes play an important role in interactions with pests and pathogens. Factors that affect production of phytochemicals are important when designing plant protection strategies that exploit these compounds to minimize crop damage caused by plant pests and pathogens. Brassicaceous plants are consumed increasingly for possible health benefits, for example, glucosinolate-derived effects on degenerative diseases such as cancer, cardiovascular and neurodegenerative diseases. Thus, factors influencing phytochemical content and profile in the production of brassicaceous plants are worth considering both for plant and human health. Even though it is known that factors that influence phytochemical content and profile may interact, studies of plant compounds were, until recently, restricted by methods allowing only a reductionistic approach. It is now possible to design multi-factorial experiments that simulate their combined effects. This will provide important information to ecologists, plant breeders and agronomists.
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Authors
Anna Maria Jönsson Susanne Harding Paal Krokene Holger Lange Åke Lindelöw Bjørn Økland Hans Peter Ravn Leif Martin SchroederAbstract
The Eurasian spruce bark beetle, Ips typographus, is one of the major forest insect pests in Europe, capable of mass-attacking and killing mature Norway spruce trees. The initiation and development of a new generation are strongly controlled by temperature and a warmer climate may affect the number of generations that is produced per year and hence the outbreak dynamics. Experimental knowledge regarding reproductive diapause adaptations is, however, too sparse for largescale assessments of future trends. We developed a model description of diapause induction, and used gridded observational temperature data to evaluate multiple combinations of day length and temperature thresholds to find the model parameterisation most coherent with I. typographus monitoring data from Scandinavia. The selected model parameterisation is supported by European literature data, though further experimental studies are required to analyse population specific adaptations and capacity for adjustments to changing climate conditions. Implementing the model description of reproductive diapause in a temperature driven model of bark beetle phenology (swarming activity and development from egg to mature bark beetle), enabled us to assess the length of the late summer swarming period that is a critical determinant of the risk of forest damage. By using regional climate model data we show that higher temperatures can result in increased frequency and length of late summer swarming events, producing a second generation in southern Scandinavia and a third generation in lowland parts of central Europe. Reproductive diapause will not prevent the occurrence of an additional generation per year, but the day length cues may restrict the length of the late summer swarming period.