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.
2004
– A method for evaluation of sustained low-level muscle activity
Kaj Bo Veiersted, Tove M. Østensvik
Authors
Kaj Bo Veiersted Tove M. ØstensvikAbstract
No abstract has been registered
Abstract
The forest stand growth simulator TRAGIC (tree response to acidification in groundwater in C) which has been developed to serve as a decision support system and a visualisation tool for scientists and forestry practitioners is introduced. TRAGIC places an emphasis upon visualisation techniques while at the same time providing detailed information on tree physiology and related parameters. The model is calibrated numerically to growth history data from two different European sites.Next, due to the importance of the visual component of the model, its ability to reproduce forest stand spatial structure is investigated, using an application of the theory of marked point processes. This analysis is applied to different experimental data sets for stands of different age, revealing information on planting schemes and the extent of significant spatial correlations.The spatial structure of the two model calibrations is then explored with the same methods. The point process analysis turns out to be a powerful diagnostic for model quality assessments, since spatial distribution is an indirect result of competition between trees for light.
Authors
Audun Øvrum Terje BirkelandAbstract
No abstract has been registered
Authors
Torild Wickstrøm Gunnar OgnerAbstract
A humus sample and a mineral soil sample were collected to investigate different sample pretreatments and their effects on the quality (mean value and uncertainty) of soil chemical data. Thirty-four humus subsamples and sixty mineral subsamples were prepared for chemical analysis. Diverse combinations of sieving, milling or grinding were utilized before the determination of Kjeldahl nitrogen (Kj-N), pH, extractable elements, and a few other chemical parameters.The humus subsamples were sieved, sieved and milled or sieved and ground. Relative to sieving, grinding improved the uncertainty in the determination by 210 times [highest for calcium (Ca), manganese (Mn), Kj-N, loss on ignition and volume weight].The mineral soil subsamples were either sieved or sieved and ground. The uncertainty was improved by 24 times for aluminum (Al), barium (Ba), Ca, hydrogen (H), potassium (K), sulphur (S), silicon (Si), zinc (Zn), and nitrogen (N) when grinding was applied.The result increased for almost all of the chemical parameters when the samples (humus and mineral) were ground in addition to sieving. The maximum increase in mean value was observed for Si (330%), iron (Fe) (200%) and carbon (C), K, magnesium (Mg), Mn, sodium (Na) (1734%).The determination of Kj-N was less influenced (016%) by different pretreatments but the uncertainty in the determination was improved up to 10 times when the sample was ground.Different sieving techniques were also utilized. It was shown that different sieving techniques altered the mean value for Ba, Fe, K, Mg, Si, Zn, pH, and loss on ignition, while the uncertainty was unaffected.All subsamples were reanalyzed after 15 months, without mixing in each sample before weighing. An increase in concentration was observed for C, Fe, phosphorus (P), S (up to 130%) and in volume weight (626%) while a decrease was observed for Ca, K, Mg, strontium (Sr), Zn (727%).
Abstract
Border cells from the seedling root tips were added to the conidium suspensions of two soilborne rootpathogens, Fusarium sp. and Cylindrocarpon sp. The presence of border cells in the suspension clearly stimulated germination of fungal conidia. Conidia of Fusarium sp. and Cylindrocarpon sp.started to germinate within 3 hours after inoculation.When border cells were washed off, the stimulating effect disappeared. Addition of malt extract caused similar stimulation as border cells. Germination of conidia was suppressed in Al-treated plants.
Abstract
Extensive monitoring of forest health in Europe has been carried out for two decades, based mainly on defoliation and discolouration. Together these two variables reflect chlorophyll amounts in the tree crown, i.e. as an indicator of foliar mass, and chlorophyll concentration in the foliage, respectively.In a current project we try to apply remote sensing techniques to estimate canopy chlorophyll mass, being a suitable forest health variable. So far, we limit this to Norway spruce only. LIDAR data here play an important role, together with optical and spectral data, either from survey flights or from satellites. We intend to model relationships between foliar mass and LIDAR data for sample trees, and then scale up this to foliar mass estimates for the entire LIDAR area.Similarly, we try to scale up chlorophyll concentrations in sample trees, by modelling a relationship between sample tree chlorophyll and hyper-spectral data. The estimates of foliar mass and chlorophyll concentrations are then aggregated to every 10x10 m pixel of a SPOT satellite scene which is also covered by airborne data, providing an up-scaled ground truth. If we are successful with this, it might be a starting point for developing a new nationwide forest health monitoring system in Norway.
Authors
Birger VenneslandAbstract
No abstract has been registered
Abstract
A home designed diffusion chamber was used during the isolation of fluoride from plant material. The chamber contained two beakers, one for the sample (milled plant material) and the other for the trapping solution (0.1M NaOH). Hexamethyldisiloxane (HMDS) in 3.5M perchloric acid was added into the sample beaker through a septum, after the chamber was closed.Fluoride in the sample reacts with HMDS and forms the volatile trimethylfluorosilane (TMFS), which is trapped and hydrolyzed to fluoride. The diffusion time was 2h and 20 samples were handled at the same time. The fluoride concentration was determined by a flow injection analysis (FIA) system using an ion selective electrode (about 50 samples/hour).The results by acid extraction were compared to the results obtained after an ashing/alkaline fusion. Both a certified sample of timothy grass (NIST 2695, high level) and more typical vegetation from forest were analyzed. For the timothy grass, the recovery increased from 48 to 84% when ashing/alkali fusion was used before the diffusion. However, higher recovery was not obtained by using ashing/alkaline fusion for the determination of fluoride in natural vegetation from forest. Acid extraction in combination with addition of HMDS was sufficient as pretreatment in these types of plant materials.The method was routinely used for the determination of fluoride both in research and forest monitoring.
Abstract
Conventional extreme value statistics and the calculation of return periods implicitly assume stationarity of distributions and statistical independence at least asymptotically (most extreme events).We demonstrate, using a collection of river runoff time series from Southern Germany, that these assumptions are invalid, and that temporal as well as spatial correlations prevail instead: temporal differences of distributions are nearly synchronized within a region, and there are systematic trends of percentiles especially at low flow conditions within the 20th century.As a consequence, the estimated return periods of a given threshold flow are fluctuating, in some cases even in a dramatic fashion. On the other hand, a general trend towards an increase in flood frequencies cannot be stated on basis of our investigations, in accordance with other recent findings (Mudelsee et al. 2003), but contrary to general expectations drawn from climate change studies.
Authors
Per Holm NygaardAbstract
No abstract has been registered