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.
2002
Abstract
The purpose of this study was to test the activity of gibberellins and auxins for induction of parthenocarpic fruit development in cloudberry, Rubus chamaemorus L., a dioecious, northern wild berry with potential for cultivation. Plant hormones were applied directly to open flowers, either dissolved in ethanol or as an aqueous spray. Of the tested gibberellins (GA1, GA3, GA4, dimethyl-GA4, GA5, GA9, GA19, GA20 and GA24) only GA1, GA3, GA4 and dimethyl-GA4 were active and induced fruit development comparable to development of pollinated fruits. Lack of activity of GA20 and GA9, the immediate precursors of GA1 and GA4, respectively, suggests that 3 b-hydroxylation of gibberellins can be inhibited in unpollinated flowers of cloudberry. Auxin treatments induced an initial fruit development, but did not result in ripe berries. Based on these results, use of transgenic methods to regulate gibberellin or/and auxin biosynthesis in carpels of cloudberry could be used to develop a parthenocarpic cloudberry.
Abstract
No abstract has been registered
Abstract
The Norwegian intensive monitoring programme of forest condition has recorded rainfall, throughfall and soil water data from 1986 at 16 forest plots. Using covariance analysis, this study has examined short term and episodic influences on soil water ionic concentration at three of the plots, and identified both seasonal and long-term temporal trends. Acidity has decreased in bulk precipitation and throughfall, and the concentrations of base cations in the organic soil horizon have increased. Nevertheless, there is evidence of continued acidification in the organic and mineral soil horizons, though of a small scale. The influence of sea salt and drought effects on soil water chemistry are examined, but found to be unimportant in causing acidification effects such as increased soil aluminium concentration.
Authors
Kjersti Holt HanssenAbstract
No abstract has been registered
Authors
Christian Anton Smedshaug Svein-Erik Lund Audun Brekke Geir Sonerud Trond RafossAbstract
Størrelse på hjemmeområde og habitatvalg for 26 hekkende kråker (Corvus corone cornix) ble registrert ved bruk av radiotelemetri i et fragmentert jord- og skogbrukslandskap i sørøst-Norge i april-juni i 1993, 1995 og 1996. Hjemmeområdet (95% minimum konveks polygon) basert på en lokalisering per dag var i gjennomsnitt 0.15 km2. Habitatsammensetningen i kråkenes hjemmeområde avvek fra habitat-sammensetningen i studieområdet, og kråkenes habitatbruk avvek fra habitat-sammensetningen i deres hjemmeområder. I begge tilfeller av habitatseleksjon rangerte kantsonen (skog < 30 m fra åpne habitat) og beitemark høyest, etterfulgt av åker, skog (>30 m fra åpne habitat) og hogstflater og plantefelt. Kråkene brukte mer tid på å sitte stille enn på å furasjere, og brukte for det meste kantsonen når den satt stille, og nesten bare beitemark og åker til å furasjere. Kråkenes bruk av kantsonen økte med økende tilgang av kantsone i hjemmeområdet, og kråkene benyttet kantsonen mer enn tilfeldig forventet så lenge kantsonen utgjorde < 40% av habitattilgangen i hjemmeområdet. Kråkenes hjemmeområde minket, når andelen av kantsone i hjemmeområdet økte. Dette antyder at en økning av andelen av kantsone mellom jordbruksmark og skog øker tettheten av hekkende kråker, og således øker predasjonsrisiko fra sittende kråker på fuglereir plassert i denne kantsonen.
Abstract
Historical reconstructions of past forest dynamics and stand structures have been used to establish reference conditions for managing present forest ecosystems. In this study we (1) developed and combined a suite of stand reconstruction techniques to describe past stand characteristics, and (2) applied these stand histories to evaluate the relationship between wood-decay fungi and forest continuity. Ten previous selectively logged stands of Norway spruce (<i>Picea abies</i> (L.) Karst.), in the middle boreal zone of southeastern Norway, were studied. We reconstructed stand structures during the 20th century using tree-ring series, growth patterns, age structures, and decay classification and datings of stumps and logs. All stands were selectively logged between 1890 and 1965, with a mean logging interval of 25 years. Harvested volumes (1900-1965) constituted 25-99% of present standing volumes and present volumes were 2.6-21 (median 4) times higher than the lowest estimated historic volumes. Dead wood was categorized into eight decay classes, where one is recently fallen, and eight is almost completely decayed. Six fungus species, assumed to indicate dead-wood continuity, were found on logs in decay classes 2-4, all of which were estimated to be<30 years old. Logs in decay classes 1-4 constituted 85% of logs >=20 cm. Expectedly, fungus abundance increased linearly with increasing number of available logs, but we failed to find a positive correlation between fungi abundance and number of old logs present (decay classes 5-8), when the effect of younger logs (2-4) was accounted for. This finding, together with the stand histories, does not lend support to the hypothesis that a continuous supply of dead wood, at the scale of forest stands, is crucial for the occurrence of the surveyed wood-decay fungi. We propose forest stand reconstructions to hold promise as a tool to assess the role of structural continuity for the occurrence of late-successional and old-growth species
Authors
Arne Sandnes Halvor SolheimAbstract
Tree resistance to the patogenic blue stain fungus Ceratocystis polonica was studied in a monoclonal stand of Norway spruce (Picea abies [L] Karst.) in relation to tree social status and diameter at breast height (DBH). The DBH distribution of the 33-year-old stand ranged from 5 to 35 cm. There were clear differences in tree height between the suppressed (DBH 7.4-10.3 cm), co-dominant (DBH 11.8-17.4 cm) and dominant (DBH 18.6-23.9 cm) tree classes. The resistance was tested by mass inoculating trees with a low (400 inoculations m-2, 60 cm inoculation belt) or high (400 inoculations m-2, 120 cm inoculation belt) dosage. The small, suppressed trees were more susceptible to inoculation than the co-dominant and dominant trees, based on amount of blue-stained and occluded sapwood, lesion length, and dead cambium/phloem. A threshold in tree social status or tree size might be important in the overall resistance to fungal infection.
Authors
Grete Rasmussen Gunnar Fremmersvik Rolf Arnt OlsenAbstract
No abstract has been registered
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No abstract has been registered
Authors
Wenche Dramstad Wendy Fjellstad Geir-Harald Strand Henrik Forsberg Mathiesen Gunnar Engan Jogeir N. StoklandAbstract
No abstract has been registered