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
No abstract has been registered
Authors
Inger Sundheim Fløistad G.G. PatilAbstract
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth.The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron.Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF.The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.
Authors
Bernt-Håvard Øyen Petter NilsenAbstract
Growth effects in a sub-alpine, low-yield Norway spruce forest in southeast Norway are reported. Sixteen sample plots of 400 m2, established 8-9 years after a mountain forest selective (MFS) cutting in the mid-1970s, were re-investigated in 2000. The selective cutting was heavy, with a mean felling volume of 72 per cent of the standing volume. Most trees in the remaining stands responded positively with increased growth after the cutting, and this was most pronounced in small and medium sized trees. A weak relationship between standing volume before and after felling, and the actual stand volume increment in the 25-year period was revealed. The felling has stimulated natural regeneration and increased the proportion of birch. The results indicate that not more than ~65 per cent of the standing volume should be cut in a single intervention if cutting cycle is less than 50 years.
Abstract
No abstract has been registered
Abstract
We investigated the effects of heavy metals (Cd, Cu, and Zn) on the enzyme activity of soil denitrifying community, and tolerance to the same heavy metals as indicated by denitrification rates. We focused on the rates of nitrate reduction to N2O and the N20 reductase activity, because the ratio between these two process rates is an indicator of the community's intrinsic capacity to release N20 to the atmosphere. A sandy loam was given a single and double dose of a heavy metal mixture (single dose = 0.32, 80, 120 mg kg 1 dry soil of Cd, Cu, and Zn, respectively). Ground straw was added together with the metals to enhance microbial growth, and the soil was incubated aerobically at 15 °C for 2 months. Kinetics of production and reduction of N20 by the denitrifying community of this soil was investigated by anaerobic incubation of soil slurries or extracted bacterial cells, using glutamate as a C source. Time courses of the N20 production and reduction curves (with and without acetylene) were used to estimate kinetic parameters to characterize the community. Heavy metal tolerance was tested by exposing extracted cells to heavy metals during such anaerobic incubations. The immediate effect (after 1 day) of heavy metals was a general reduction of the denitrification rate but also to decrease the N20 reduction more than N20 production rate. N20 production was partly recovered 8 days after heavy metal introduction, and completely restored (equal to the control soil) after 2 months. In contrast, the N20 reductase activity was still not completely restored after 2 months. Exposure of extracted cells to the different heavy metals showed that soil exposure of heavy metals had induced an increased Cd-, Cu-, and Zn-tolerance of N20 reductase activity. Simulation of the NO production and reduction curves during the anaerobic incubation allowed an estimation of the apparent specific growth rate by fitting the simulated to the measured curves. Estimated growth rates were significantly lowered as the community heavy metal tolerance developed (heavy metal exposed soil after 2 months versus control soil), possibly reflecting a metabolic burden of the metal resistance mechanisms.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Cleaning of containers to counteract infection that might cause root dieback should remove old, adhering media and roots that may harbour pathogens. This study investigated seedling growth and the number of viable fungal propagules retained on the container cavity walls as a result of different container cleaning treatments: washing with cold water (ca 8C) only, or in addition with a bath temperature of 60, 70, 80 or 95C for 30 seconds.More fungal propagules were isolated from containers washed in cold water, than from the other treatments. The most frequently isolated fungi were Paecilomyces sp. and Penicillium sp., which are well known saprophytes. Bacteria and yeast did not seem to be affected by the washing.Electron microscopy studies of container cavity walls revealed many organic particles and fungal spores on the walls of coldwashed containers. Among other fungal spores there were visible chains of Paecilomyces spp. spores.Containers that were washed at 80C had some organic debris attached to the cavity walls, but no spores were visible. In used and unwashed containers fungal spores, hyphae and organic debris were found on the container cavity walls. Containers in which the major part of the seedlings previously had suffered from root dieback might have contained a considerable amount of inoculum before washing.Almost 60% of the seedlings grown in unwashed containers had dead or very stunted root systems, whereas about 10% of the seedlings in cold washed containers suffered from severe root dieback. Additional warm water treatment further reduced the root dieback of this group of containers. In unwashed containers in which healthy seedlings had been grown, about 4% seedlings and after cold washing no seedlings with root dieback were observed.The cold washing procedure had a positive effect on seedling height, but there was no additional effect of the warm water treatment. We conclude that cold pressurised washing alone does not provide adequate control of root dieback and that an additional warm water bath of at least 60C is recommended.
Authors
Oddvar Skre R. Baxter R.M.M. Crawford T.V. Callaghan A. FedorkovAbstract
Modeling studies indicate that if the global warming persists over centuries, the tundra-taiga boundary will move northwards. However, on a regional scale large variations may exist, and in oceanic areas a southwards retreat may also be expected. This tendency is reinforced by human activity, in particular in northern Russia. Local changes over short periods therefore requires continuous observation and monitoring of treeline movement, from an economic as well as forecology and conservation.
Authors
Peder Gjerdrum I. AkerfeldsAbstract
No abstract has been registered