Blar i Institutt for natur, helse og miljø på forfatter "Bjerketvedt, Dag"
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Analysis of DNA polymorphism in wild populations of herb-Paris (Paris quadrifolia L., Trilliaceae) from Lithuania and Norway.
Jogaitė, Vaida; Lazutka, Juozas R.; Naujalis, Jonas; Stapulionyte, Asta; Odland, Arvid; Bjerketvedt, Dag (Journal article; Peer reviewed, 2006)Analysis of random amplified polymorphic DNA (RAPD) was used to determine genetic diversity within the populations of herb-Paris plant from Lithuania and Norway. RAPD analyses have shown 21.9 ± 5.2% of polymorphic loci in ... -
Are trampling effects by wild tundra reindeer understudied?
Heggenes, Jan; Odland, Arvid; Bjerketvedt, Dag (Journal article; Peer reviewed, 2018)Grazing and trampling by the wide-ranging wild tundra reindeer may have major top down landscape effects by causing vegetation changes. Grazing, as the collective effect of eating, trampling, defecation, and urination, has ... -
Blitzfotografering av bevegelige objekter gjennom mikroskop
Bjerketvedt, Dag (Journal article, 1981)Ordinary microscopes can be adapted to fully automatic photomicroscopes for use with flash. An automatic small film camera with an autodynamic flash and extra equipment for microphotography is necessary. The camera's ... -
Estimation of lichen biomass with emphasis on reindeer winter pastures at Hardangervidda, S Norway
Odland, Arvid; Sandvik, Sylvi M.; Bjerketvedt, Dag; Myrvold, Linn L. (Journal article; Peer reviewed, 2014)Quantification of lichen abundance is important for management of reindeer populations. We measured dry lichen biomass in 876 micro plots (16.5 cm - 16.5 cm) systematically sampled within 219 vegetation plots (2 m - 2 m) ... -
Herbivore grazing—or trampling? Trampling effects by a large ungulate in cold high- latitude ecosystems
Heggenes, Jan; Odland, Arvid; Chevalier, Tomas; Ahlberg, Jörgen; Berg, Amanda; Larsson, Håkan; Bjerketvedt, Dag (Journal article; Peer reviewed, 2017)Mammalian herbivores have important top-down effects on ecological processes and landscapes by generating vegetation changes through grazing and trampling. For free-ranging herbivores on large landscapes, trampling is an ... -
Makrofotografering med blitz av objekter i mørkefelt
Bjerketvedt, Dag; Andersen, Ragnvald (Journal article; Peer reviewed, 1984) -
Petrifilm TM som alternativt medium for dyrking av bakterier i vann
Rosef, Olav; Odland, Arvid; Bjerketvedt, Dag (Journal article, 2002)Metoden NS-EN ISO 6222 er sammenlignet med Petrifilm for påvisning og telling av mikroorganismer i overflatevann (råvann) og i drikkevann (behandlet vann). De dyrkingstemperaturene som gjeldende drikkevannsforskrift angir ... -
Reinsdyrstammen på Hardangervidda for stor
Bjerketvedt, Dag (Journal article, 1981)Hardangervidda, in Southern Norway, is the largest mountain plateau in Europe (Fig. 1). It is approximately 10000 km2 in area and lies mostly between 1100 and 1300 m a.s.l. The topography and vegetational cover produce a ... -
Superoxide dismutase polymorphisms in wild populations of herb Paris (Paris quadrifolia L., Trilliaceae)
Jogaitė, Vaida; Kleizaitė, Violeta; Stapulionyte, Asta; Bjerketvedt, Dag (Journal article, 2003)Polymorphism of superoxide dismutase (SOD) was investigated in leaves of herb Paris (Paris quadrifolia L., Trilliaceae). The plants were collected during the summer and autumn of 2001 from different natural locations in ... -
The growth and phenology patterns of herb Paris (Paris quadrifolia L., Trilliaceae): relation to soil and air temperatures
Bjerketvedt, Dag; Odland, Arvid; Lazutka, Juozas R.; Naujalis, Jonas (Journal article; Peer reviewed, 2003)The phenology and development of Paris quadrifolia L. has been related to variations in soil and air temperatures during four seasons (1997-2000). Its emergence appeared to be strongly dependant on soil temperature. Plants ... -
The Hardangervidda wild reindeer herd: a problematic management history
Bjerketvedt, Dag; Reimers, Eigil; Parker, Howard; Borgstrøm, Reidar (Journal article; Peer reviewed, 2014)The unique and internationally important wild reindeer Rangifer tarandus herd on the Hardangervidda plateau of southern Norway has shown frequent and extreme fluctuations in harvest numbers for the past 60 years, despite ...