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.
2007
Abstract
No abstract has been registered
Authors
Atle Mysterud Erling Meisingset Vebjørn Veiberg Rolf Langvatn Erling Johan Solberg Leif Egil Loe Nils Christian StensethAbstract
Proper management of wildlife relies on metrics of population development. Typically, the best estimation techniques are too expensive for coarse-scale management. In marine fisheries, catch-per-unit effort is commonly used, but problems may arise due to changes in spatial harvest effort or in habitat use as density changes. Managers in Norway are in the early phases of implementing "seen deer" during harvesting and "spring counts" on farmland as a means of monitoring red deer Cervus elaphus populations. We provide a first evaluation of how suitable these methods are by comparing the results with population estimates obtained using cohort analysis, and by analysing the within-season variation in number of seen deer. "Seen deer" predicted annual increases in populations fairly well. Adjusting for harvesting effort provided less good estimates, due to a proportionally larger increase in effort relative to deer population size as population size increased. The number of seen deer per day decreased rapidly at the beginning of the season, and then levelled off or increased slightly during the rut, especially on farmland. The number of seen deer increased both with the number of harvesters and hours harvested, but at a diminishing rate. The current practice of "spring counts" was not successful in predicting population changes, probably due to a lack of replication. Indeed, date strongly affected the number of deer seen during spring counts. While "seen deer" seems to be a very promising tool for monitoring population size of red deer, there are some limitations to the practice as implemented for moose Alces alces in Scandinavia due to a more complex relationship with harvesting effort. Our study highlights that the large number of hours harvesters observe wildlife can provide a useful tool for population monitoring. However, the use of such indices may vary between species and according to harvest techniques and should thus be assessed with care before implementation
Authors
Bjørn Mejdell Larsen Paul E. Aspholm Hans M. Berger Karstein Hårsaker Leif R. Karlsen Jon Magerøy Kjell Sandaas Jan Henrik SimonsenAbstract
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Authors
Hans Haavardsholm Blom Elena A. Ignatova Olga M. AfoninaAbstract
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Authors
Janneche Utne Skåre Jan Alexander Augustine Arukwe Trine Eggen Gunnar Sundstøl Eriksen Christiane Kruse Fæste Kari Grave Helle Katrine Knutsen Amund Måge Anders RuusAbstract
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Authors
Ingunn Molund Vågen Trygve Aamlid Arne Oddvar SkjelvågAbstract
The effects of three nitrogen (N) fertilizer rates (0, 120, and 240 kg N ha(-1)) and two planting times (May or late June/July) on yield and N use of the early cultivar 'Milady' and the late cultivar 'Marathon' of broccoli (Brassica oleracea var. italica) were investigated on three silty loam soils varying in soil mineral N (Nmin) in the southernmost part of Norway during 1999 and 2001. In all crops receiving fertilizer, rapid uptake of N started about three weeks after planting. The relative yield of broccoli heads increased with increasing soil available N (fertilizer N plus Nmin) at planting to 200-250 kg N ha(-1) and then levelled off. The two lower fertilizer rates were more restrictive to yields in early-planted than in late-planted crops. A general increase in harvest index with increasing N rate reflected a stronger effect of N on the head yield than on the total above ground biomass production. The apparent recovery of fertilizer N decreased with increasing N rate and was on average 74% in total above ground biomass and 25% in broccoli heads. Despite a higher N uptake, the average soil mineral N level at harvest increased from 12 kg N ha(-1) on unfertilized plots to 27 and 78 kg N ha(-1) on plots receiving 120 and 240 kg N ha(-1), respectively; this increase was stronger in early than in late plantings and stronger in 'Milady' than in 'Marathon'. The yield of broccoli heads was similar in the two cultivars, but 'Milady' had a lower total biomass production and thus a higher harvest index, presumably due to earlier head initiation.
Authors
Guro Ådnegard Skarstad Svein Ole BorgenAbstract
No abstract has been registered