Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2007
Sammendrag
River floods may cause considerable damage. Water management strategies intend tomoderate or mitigate the severe effects of extreme discharge events. In this context,techniques for the detection and attribution of changes is of crucial importance. Extremeflood events seem to occur more frequently in recent decades in central Europe.It is anticipated that climate change and weather regime shifts may contribute to this...
Forfattere
Carl Gunnar FossdalSammendrag
In collaboration with the NARC platform at Ås, we have taken the Norway spruce phytochrome and PaChi4 promoters and introduced them into Arabidopsis using GFP and YFP expression vectors in order to study their effect on expression under long and short day treatment. Said in other words we use of GFP and YFP as reporters and Arabidopsis as a host for the Norway spruce promoters in order to study their possible regulation by day-length in this model plant system. In completely separate experiments in collaboration with the NARC platform at Ås, we have introduced the Norway spruce glycohydrolase PaChi4 into Arabidopsis to examine what effect this might have on the response to wounding and to pathogens. The PaChi4 enzyme is produced at very high levels in tissues with high level of host cell death (PCD) following fungal infections and it might be a marker for or directly involved in PCD. We have obtained transgenic plants and the first examination for any day-length dependent expression of the GFP and YFP reporters in the transgenic Arabidopsis lines is currently being pursued while the examination of the PAChi4 enzyme overexpressing lines are yet to be initiated.
Sammendrag
Ecological studies are often confronted with short and fragmented or unevenly sampled time series. Examples are, e.g., time series of biogeochemical fluxes measured on a variety of scales. Characterizing the observed time series patterns, particularly the correlation structure is crucial for an integrated ecosystem assessment or possibly for improved processes understanding.
Forfattere
John Derome Per Arild Aarrestad Paul Aspholm Vegar Bakkestuen Jarle Werner Bjerke Kjell Einar Erikstad Minna Hartikainen Ludmila Isaeva Martti Lindgren Antti-Jussi Lindroos Tor Myking Jarmo Poikolainen Pasi Rautio Ingvald Røsberg Maija Salemaa Hans Tømmervik Natalya VassilievaSammendrag
Det er ikke registrert sammendrag
Forfattere
Pavel Cudlín Barbara Kieliszewska-Rokicka Maria Rudawska Tine Grebenc Odair Alberton Tarja Lehto Mark R. Bakker Isabella Børja Bohdan Konôpka Tomasz Leski Hojka Kraigher Thomas W. KuyperSammendrag
Det er ikke registrert sammendrag
Forfattere
Holger LangeSammendrag
The net ecosystem productivity (NEP) of a sequence of threemonoaged Norway spruce stands located in southeast Norway is modelled using the biogeochemical model Biome-BGC. For calibration, we use estimated biomass stocks at the plot level and Leaf Area Index measurements. The model is run for 30 years of historical temperature measurements as well as for a regional climate scenario. It is shown that under current conditions, NEP develops from negative values for a young stand (30 years) to clearly positive for a middleaged (60 years) to slightly negative again for a very old and decaying stand (120 years). However, the old stand benefits substantially from the predicted increased temperatures in the climate scenario, rendering NEP positive again. For the 30 and 60 years stands, almost no change is predicted from Biome-BGC.
Sammendrag
Furfurylated wood has shown to have promising properties for a wood modification agent during the last years. In this paper, an alternative curing method for furfuryl alcohol modified pine sapwood by means of microwave radiation was investigated. Different process parameters of microwave treatment such as output power, exposure time to microwave radiation, initial wood moisture content and evaporation during treatment, were tested. The weight percent gain of pine wood samples due to polymerised furfuryl alcohol was investigated by means of thermo gravimetric analysis. Leaching of furfuryl treated and differently cured samples gave information about the degree of fixation. No distinct influence of initial moisture content could be stated. A slight tendency of improving the degree of fixation by increasing the consumption energy of wood samples due to microwave energy was found. Changing the evaporation ability of samples during microwave treatment by using plastic foil had no distinct influence. Fixation of furfuryl alcohol could be improved by microwave treatment, and a degree of fixation above 90 % was calculated. However, the fixation was lower than in oven cured samples.
Forfattere
Peder GjerdrumSammendrag
Predicting sawn timber yield continues to be a challenging task, influenced by several stochastic processes. In this paper, a simulation model for main yield and sideboards in softwood sawing is presented. Predicting sawn timber yield usually involves either straight and notional mathematics, or empiric figures, both with inherent drawbacks. Most geometric models fail to take into consideration random variation: in log position when entering the saw, no log being perfectly straight, smooth and circular, sawing accuracy, etc., and therefore systematically overestimate the yield, in particular the sideboards...
Forfattere
Ole Martin Bollandsås Kjersti Holt Hanssen Solfrid Marthiniussen Erik NæssetSammendrag
The relationships between measures of forest structure as derived from airborne laser scanner data and the variation in quantity of young trees established by natural regeneration in a size-diverse spruce forest were analyzed. A regeneration success rate (RSR) was regressed against 27 different laser-derived explanatory variables. The 27 different models were ranked according to their Akaike information criterion score. Each laser variable was then associated with two categories. These were return and type. Within the return and type categories, the variables were grouped according to if they originated from first or last return echoes and if they were canopy height or canopy density metrics. The results show that the laser variables strongest correlated to the quantity of small trees could be attributed to last return and density metrics.
Forfattere
Miguel D. Mahecha Markus Reichstein Holger Lange Nuño Carvalhais T. Grünwald Dario Papale G. SeufertSammendrag
Characterizing ecosystem-atmosphere interactions in terms of carbon and water exchange on different time scales is considered a major challenge in terrestrial biogeochemical cycle research. The respective time series currently comprise an observation period of up to one decade. In this study, we explored whether the observation period is already sufficient to detect cross-relationships between the variables beyond the annual cycle, as they are expected from comparable studies in climatology. We investigated the potential of Singular System Analysis (SSA) to extract arbitrary kinds of oscillatory patterns. The method is completely data adaptive and performs an effective signal to noise separation. We found that most observations (Net Ecosystem Exchange, NEE, Gross Primary Productivity, GPP, Ecosystem Respiration, Reco, Vapor Pressure Deficit, VPD, Latent Heat, LE, Sensible Heat, H, Wind Speed, u, and Precipitation, P) were influenced significantly by low-frequency components (interannual variability). Furthermore, we extracted a set of nontrivial relationships and found clear seasonal hysteresis effects except for the interrelation of NEE with Global Radiation (Rg). SSA provides a new tool for the investigation of these phenomena explicitly on different time scales. Furthermore, we showed that SSA has great potential for eddy covariance data processing, since it can be applied as a novel gap filling approach relying on the temporal correlation structure of the time series structure only.