Tone Birkemoe

What window traps can tell us: effect of placement, forest openness and beetle reproduction in retention trees

The use of flight interception traps (window traps) has been criticized for catching too many species without affinity to the immediate surroundings. We study aspen retention trees left for conservation reasons in a boreal forest in south-eastern Norway, and investigate how placement of window traps affects the beetle species assemblage, abundance of habitat specialists, saproxylic species and vagrant species. We also test the correlation between beetle trappings and beetle exit holes in wood. The window traps clearly responded to the immediate surroundings of the trap. Traps located on tree trunks had a different species assemblage than traps hanging freely. Traps mounted on trees caught more aspen associated beetles and less vagrant species than their free-hanging counterparts. The differences were larger when trees were dead than alive. There was a significant positive correlation between presence of individuals in the trunk-window traps and presence of exit holes for three aspen associated species. Thus, the trapping results indicated successful reproduction, showing that aspen associated beetles are not only attracted to but also utilise aspen retention trees/high stumps left in clear-cuts. This indicates that this conservation measure in forest management can have positive, alleviating effects concerning the dead wood deficit in managed boreal forest.

Head lice prevalence among households in Norway: importance of spatial variables and individual and household characteristics

SUMMARY Head lice prevalence varies greatly between and within countries, and more knowledge is needed to approach causes of this variation. In the present study, we investigated head lice prevalence among elementary school students and their households in relation to individual and household characteristics as well as spatial variables. The investigation included households from 5 geographically separated municipalities. Present infestations among household members as well as previous infestations in the household were reported in a questionnaire. In elementary school students prevalence was low (1·63%), but more than one-third of the households (36·43%) had previously experienced pediculosis. Prevalence was higher in elementary school students than in other household members, and highest in third-grade children. Prevalence was also influenced by the school attended, which suggested that interactions between children in the same school are important for head lice transmission. Previous occurrence of head lice in homes also increased the risk of present infestation. Prevalence of previous infestations was higher in households with more children and in more densely populated municipalities, indicating that the density of hosts or groups of hosts influences transmission rates. These results demonstrate that information of hosts’ spatial distribution as well as household and individual characteristics is needed to better understand head lice population dynamics.

Does collembolan grazing influence nitrogen fixation by cyanobacteria in the high Arctic

Abstract A field experiment was performed to test whether cyanobacterial nitrogen fixation rates increase or decrease when exposed to low and moderate microarthropod grazing intensities. The densities of naturally occurring Collembola, i.e. Hypogastrura viatica, were manipulated on a salt marsh covered with cyanobacteria in the high Arctic, Svalbard. Nitrogen-fixation rates in grazed cyanobacterial crust were measured and used as an indirect measurement of cyanobacterial biomass on three dates during one summer. After 30 days, a second order polynomial regression gave a good fit to the data, indicating an increase in nitrogen-fixation rates at low/intermediate grazing pressures and a decrease at high grazing pressures. Thus, grazing collembolans may influence the nitrogen-fixation rates in an arctic salt-marsh community. Although based on a small set of data, the study indicates a compensatory fixation at low grazing pressures followed by a reduction at high grazing pressures.

Blowfly (Diptera, Calliphoridae) damage on stockfish in northern Norway: pest species, damage assessment and the potential of mass trapping

Production of high quality stockfish in northern Norway takes place from February to May. The dominant blowfly species (Diptera: Calliphoridae) with adults present during stockfish production were Calliphora vicina and Protophormia terraenovae. Larval collections identified the damage-causing species to be C. vicina. Other saprophagous blowfly species were only found after the production period. Fish dried in sun-exposed locations experienced more damage than fish in shaded locations, and the risk of damage was higher in fish dried later in the production period. Yellow sticky traps and funnel traps baited with dimethyl trisulphide were tested for their potential in mass trapping. Sticky traps caught flies during early spring, while funnel traps increased in efficiency closer to summer. Attraction to dimethyl trisulphide was found to be significantly higher for C. vicina compared to P. terraenovae, and the catch of C. vicina consisted of 92% females. The catch of female flies during the critical drying period consisted of 5–30% of the estimated number of flies having caused damage. The target specificity with high female catches and the cost efficiency of these traps indicate that mass trapping can be used as an integrated part of a management program to reduce damage from blowflies in stockfish producing areas.

Phenology and life history of the blowfly Calliphora vicina in stockfish production areas

Calliphora vicina Robineau‐Desvoidy (Diptera: Calliphoridae) causes yearly losses of 1–2 million Euros to the stockfish industry in Lofoten, Norway. To develop an efficient management program, knowledge of its life cycle and phenology in production areas is needed. Cohort studies in a simulated Lofoten climate showed that field abundance peaks of adults in early spring and midsummer can be explained by a cohort originating from stockfish and its subsequent generations. Laboratory simulations with normal, increased, and decreased Lofoten temperatures indicate that C. vicina overwinter as a mix of larvae, pupae, and adults, and a temperature change of ± 2 °C significantly influences reproductive timing, reproductive output, and female mortality. Flies originating from stockfish reproduced during the first summer when temperatures were increased 2 °C above normal. At lower temperatures, the reproductive investment was low or absent during the first summer and the adult flies entered the winter in a diapausing state. Most offspring produced during the first summer and autumn developed continuously without maternally induced diapause, pupated during the winter, and hatched in the early spring to co‐occur with their parent generation during stockfish production. Calliphora vicina showed flexibility in reproductive efforts and overwintering strategies. The high proportion of adults overwintering compared with the commonly used larval diapause strategy might be interpreted as an adaptation to exploit the stockfish resource. The majority of female C. vicina that cause damage to stockfish likely developed on fish dried the previous year, and a continuous year‐long trapping is recommended to decimate the population.

Priority effects of early successional insects influence late successional fungi in dead wood

Abstract Community assembly is an integral process in all ecosystems, producing patterns of species distributions, biodiversity, and ecosystem functioning. Environmental filters and colonization history govern the assembly process, but their relative importance varies depending on the study system. Dead wood decomposition is a slow process, allowing decomposer communities to develop within a slowly changing substrate for decades. Despite this, there are few long‐term studies of priority effects from colonization history in this ecosystem. In this study, we investigate the importance of insects in early succession of dead wood on the fungal community present one decade later. Sixty aspen trees were killed in two study landscapes, each tree producing one aspen high stump and log. Insects were sampled with flight interception traps during the first 4 years after tree death, and fungal fruiting bodies were registered in year twelve. We found positive priority effects of two fungivorous beetles, the sap beetle Glischrochilus quadripunctatus and the round fungus beetle Agathidium nigripenne, on the Artists bracket (Ganoderma applanatum) and a positive priority effect of wood‐boring beetles on the ascomycete Yellow fairy cup (Bisporella citrina). The Aspen bracket (Phellinus tremulae) did not respond to insects in early succession of the dead wood. Our results suggest that early successional insects can have significant, long‐lasting effects on the late successional fungal community in dead wood. Also, the effect can be specific, with one fungus species depending on one or a few fungivorous beetle species. This has implications for decomposition and biodiversity in dead wood, as loss of early colonizing beetles may also affect the successional pathways they seem to initiate.

Head Lice in Norwegian Households: Actions Taken, Costs and Knowledge

Introduction Head lice infestations cause distress in many families. A well-founded strategy to reduce head lice prevalence must shorten the infectious period of individual hosts. To develop such a strategy, information about the actions taken (inspection, treatment and informing others about own infestations), level of knowledge and costs is needed. The present study is the first to consider all these elements combined. Materials and Methods A questionnaire was answered by 6203 households from five geographically separated municipalities in Norway. Results 94% of the households treated members with pediculicides when head lice were discovered. Nearly half of the households checked biannually or not at all. Previous occurrence of head lice and multiple children in a household improved both checking frequency and method. More than 90% of the households informed close contacts about their own pediculosis. Direct costs of pediculosis were low (less than €6.25 yearly) for 70% of the households, but the ability to pay for pediculicides decreased with the number of head lice infestations experienced. One in three households kept children from school because of pediculosis. Other widespread misconceptions, such as that excessive cleaning is necessary to fight head lice, may also add unnecessary burden to households. School affiliation had a significant effect on checking frequency and method, knowledge and willingness to inform others about own pediculosis. Conclusions Increased checking frequencies appear to be the most important element to reduce head lice prevalence in Norway and should be a primary focus of future strategies. National campaigns directed through schools to individual households, might be an important tool to achieve this goal. In addition to improving actions taken, such campaigns should also provide accurate information to reduce costs and enhance the level of knowledge about head lice in households.

Specialists in ancient trees are more affected by climate than generalists.

Abstract Ancient trees are considered one of the most important habitats for biodiversity in Europe and North America. They support exceptional numbers of specialized species, including a range of rare and endangered wood‐living insects. In this study, we use a dataset of 105 sites spanning a climatic gradient along the oak range of Norway and Sweden to investigate the importance of temperature and precipitation on beetle species richness in ancient, hollow oak trees. We expected that increased summer temperature would positively influence all wood‐living beetle species whereas precipitation would be less important with a negligible or negative impact. Surprisingly, only oak‐specialist beetles with a northern distribution increased in species richness with temperature. Few specialist beetles and no generalist beetles responded to the rise of 4°C in summer as covered by our climatic gradient. The negative effect of precipitation affected more specialist species than did temperature, whereas the generalists remained unaffected. In summary, we suggest that increased summer temperature is likely to benefit a few specialist beetles within this dead wood community, but a larger number of specialists are likely to decline due to increased precipitation. In addition, generalist species will remain unaffected. To minimize adverse impacts of climate change on this important community, long‐term management plans for ancient trees are important.

Experimental warming increases herbivory by leaf‐chewing insects in an alpine plant community

Abstract Climate warming is predicted to affect species and trophic interactions worldwide, and alpine ecosystems are expected to be especially sensitive to changes. In this study, we used two ongoing climate warming (open‐top chambers) experiments at Finse, southern Norway, to examine whether warming had an effect on herbivory by leaf‐chewing insects in an alpine Dryas heath community. We recorded feeding marks on the most common vascular plant species in warmed and control plots at two experimental sites at different elevations and carried out a brief inventory of insect herbivores. Experimental warming increased herbivory on Dryas octopetala and Bistorta vivipara. Dryas octopetala also experienced increased herbivory at the lower and warmer site, indicating an overall positive effect of warming, whereas B. vivipara experienced an increased herbivory at the colder and higher site indicating a mixed effect of warming. The Lepidoptera Zygaena exulans and Sympistis nigrita were the two most common leaf‐chewing insects in the Dryas heath. Based on the observed patterns of herbivory, the insects life cycles and feeding preferences, we argue that Z. exulans is the most important herbivore on B. vivipara, and S. nigrita the most important herbivore on D. octopetala. We conclude that if the degree of insect herbivory increases in a warmer world, as suggested by this study and others, complex interactions between plants, insects, and site‐specific conditions make it hard to predict overall effects on plant communities.

Trophic levels and habitat specialization of beetles caught on experimentally added aspen wood: Does trap type really matter?

Saproxylic (wood living) beetles make up an important part of forest biodiversity and are of importance for conservation practices. The beetles are commonly surveyed on various dead wood resources by use of flight interception traps (window traps), catching both species depending on the resource and vagrant (irrelevant) species. Enclosed traps have been suggested as an alternative sampling method, as they sample only the beetles utilizing the dead wood resource. This is the first study to compare the two trap types based on catches from experimentally added identical wood units. Our main aim was to test whether enclosed window traps catch a higher proportion of specialized species and species of a lower trophic level than open window traps, and whether proportions of vagrant species decrease with habitat specialization and trophic level in both trap types. The study was carried out during two summers with traps mounted on replicated, identical units of fresh aspen dead wood in boreal forest in south-eastern Norway. Contrary to our expectations and earlier findings, the enclosed window traps did not catch a higher proportion of habitat specialists (aspen-associated species) or species at the lowest trophic level (wood feeding) compared to the open traps. Rather, the proportion of predators was higher and fungivores lower in enclosed versus open window traps, and no difference was found between different categories of habitat specialization. The proportion of vagrant species was lowest among the beetles with the strongest specialization (aspen-associated) whereas there was no difference with trophic levels. We suggest that keeping vagrants but selecting species based on host tree affinity is the best way to use catches from open window traps on dead wood units. Studies of predators and fungivores should be interpreted with care.