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.
2006
Authors
Heleen A. de Wit Taru Palosuo Gro Hylen Jari LiskiAbstract
Growing stocks of trees in Europe have increased in a magnitude that is significant in terms of carbon (C) sink strength. Estimates of the soil C sink strength that this increased stock of trees may have induced on a regional scale are scarce, uncertain and difficult to compare. This illustrates the need for a widely applicable calculation method. Here, we calculate a C budget of productive forest in southeast Norway based on forest inventory information, biomass expansion factors (BEF), biomass turnover rates and the dynamic soil model Yasso. We estimate a 29% increase (112-145 Tg) of C in biomass between 1971 and 2000, and estimate the associated increase of C in soils (including dead wood) to be 4.5% (181-189 Tg). The C sink strengths in biomass and soils (including dead wood) in 1990 are 0.38 and 0.08 Mg ha(-1) yr(-1), respectively. Estimated soil C density is 58 Mg C ha(-1) or ca 40% of measured soil C density in Norwegian forest soils. A sensitivity analysis - using uncertainty estimates of model inputs and parameters based on empirical data - shows that the underestimation of the soil C stock can be due to overestimation of decomposition rates of recalcitrant organic matter in the soil model and to including only trees as a source of litter. However, uncertainty in these two factors is shown to have a minimal effect on soil sink estimates. The key uncertainty in the soil sink is the initial value of the soil C stock, i.e. the assumed steady state soil C stock at the start of the time series in 1970. However, this source of uncertainty is reduced in importance for when approaching the end of the data series. This indicates that a longer time series of forest inventory data will decrease the uncertainty in the soil sink estimate due to initialisation of the soil C stock. Other, less significant, sources of uncertainty in estimates of soil stock and sink are BEF for fine roots and turnover rates of fine roots and foliage. The used method for calculation of a forest C budget can be readily applied to other regions for which similar forest resource data are available.
Abstract
No abstract has been registered
Authors
Peder Gjerdrum Mauro BernabeiAbstract
Vridd vekst gir opphav til hellende fiber, som øker tørkedeformasjonene og reduserer styrken i trelast. Resultater fra nyere nordisk forskningblir her presentert for det italienske publikum, med utgangspunkt i egne undersøkelser (se bl.a. Oppdragsrapport 7/2000). En enkel modell for fibervinkel i en granstamme blir foreslått. Modellen har to parametre og er basert på én prediktor: avstand fra marg. Normalverdier og spredning for de to parametrene er oppgitt for nordiske forhold.
Abstract
The paper describes the development of the two involved nurseries and the reforestation efforts and results on the two experimental sites at Munda and in Mahamaya
Authors
Ketil KohmannAbstract
Feeding by the Tarnished Plant Bug (Lygus rugulipennis Popp.) has caused severe damage in Norwegian nurseries. Large quantities of seedlings have been removed after sorting. The life cycle of the insect has been well studied and documented. This study was a first attempt to investigate how the seedlings develop after the insect attacks.The first visible sign of damage is the development of multiple terminal buds. Two-year-old containerised seedlings were planted and followed for four years. Before planting, the seedlings were sorted into three damage classes, (0) undamaged, (I) moderately damaged; up to ten fully developed buds, and (II) severely damaged; from ten to twenty small buds and without any dominant apical bud.The damaged seedlings were somewhat shorter at planting but this difference disappeared with time. The seedlings in the two damaged classes differed in their development of multiple shoots. At the end of the four-year period about 50 % of the seedlings in ClassII and about 20 % from Class I still had multiple leaders, or lateral stems or side branches that would probably in the future produce spike knots. The sorting routine currently used at the nursery was found to reduce the problem to an acceptable level for seedlings that were planted in the forest.
Abstract
The minirhizotron technique provides the opportunity to perform in situ measurements of fine root dynamics and obtain accurate estimates of fine root production and turnover. The objective of the present work was to determine the fine root longevity and mycorrhization in a Norway spruce chronosequence. The study was carried out on four stands of planted Norway spruce (Picea abies), approximately 10, 30, 60 and 120 years old, during 2001 and 2002. The stands were located at Nordmoen, a plain of sandy deposits in southeast Norway (60o15 N, 11o06 E). For the root turnover study, altogether 60 minirhizotrones were installed and images were processed.Individual fine roots were identified, their mycorrhization assessed, appearance and possible disappearance dated, and growth in length measured. The data set was subjected to a survival analysis, using a Kaplan-Meier product-limit approach. The minirhizotron samples were stratified according to stand age class, and Coxs F-test was used to analyze differences in survival estimates. The analysis may also be extended to consider other covariates such as tree species (spruce, pine or birch), understory vegetation, or soil depth. Typical survival function estimates will be presented, and the influence of stand age on the mycorrhization and the dynamics of the fine roots will be discussed.
Abstract
Based on field observations of leaf morphology and variation in chloroplast DNA (cpDNA) in Scandinavia, Norway has been suggested as a suture zone for elm (Ulmus glabra) from different glacial refugia. The aim of this paper was to study the geographical concordance between the maternally inherited cpDNA markers (16 populations) and the assumed polygenic and biparentally inherited leaf traits, studied in a field trial (five populations).Two cpDNA haplotypes were detected, but without geographical structure. Leaf traits showed a gradient from typical ssp. montana traits (relatively long, long tapering, absent acute lobes) in western populations to more ssp. glabra-like traits (relatively broad, short tapering, acute lobes present) in eastern and northern populations.The overall geographical concordance between haplotype distribution and leaf traits was limited, probably owing to different inheritance of cpDNA and leaf traits, but the spatial variation in leaf traits and cpDNA in a subset of common populations (n=5) was compatible with a dual migration of elm to Scandinavia. Both measures suggest a broad suture zone, covering the entire distribution of elm in Norway.The results are discussed in relation to the use of maternally inherited markers, such as cpDNA, in delimiting suture zones.
Authors
Erlend Ystrøm Haartveit Per Otto FlæteAbstract
The optimal utilisation of a wood raw material is dependent on the wood properties. In this study near infrared (NIR) spectroscopy was used to non-destructively predict density, modulus of elasticity, and modulus of rupture for small clear specimens cut from Picea abies (L.) H. Karst. (Norway spruce) trees.NIR spectra were recorded directly on the wood surface of each specimen as close as possible to the fracture developed during the bending test. Models were calibrated using partial least squares regression. The validation method was test set validation by data splitting.The correlation between predicted and measured values was highest for modulus of elasticity (0.86), followed by modulus of rupture (0.84) and density (0.79). The validation of the models showed that the average accuracies of predictions were 20.3 kg/m3 for density, 1.1 GPa for modulus of elasticity, and 6.1 MPa for modulus of rupture.Results are comparable to what has been found for other tree species, such as Pinus radiata D. Don (radiata pine), Pinus taeda L. (loblolly pine), and Larix decidua Mill. (European larch). Models for predicting density, modulus of elasticity, and modulus of rupture based on NIR spectra outperformed simple regression models using the mean annual ring width as the independent variable.NIR spectroscopy is a rapid tool for characterising organic materials. It requires minimal sample preparation and spectra are collected on solid wood, rapidly and nondestructively. For these reasons the method should be tested in production lines for lumber. In future research we aim for reliable predictions of mechanical properties of industrially manufactured lumber using models based on NIR spectroscopy and multivariate statistical methods.
Authors
Kjersti Holt Hanssen M. LiuAbstract
The use of partial cuttings in spruce (Picea abies L. Karst.) stands is increasing in Norway, especially at sites where special consideration must be taken regarding biodiversity or the recreational value of the forest. However, obtaining sufficient numbers of vital natural regeneration using partial cuttings can be challenging in the Nordic countries, due to harsh climatic conditions and tough competition.We wanted to relate the establishment and growth of natural spruce regeneration to soil conditions and understorey light levels using a thirteen year old field trial with different types of partial cuttings. The field trial was established in a Norway spruce forest on a hillside with varying soil conditions in Oslo, SE Norway. The harvesting treatments included thinning from above, single-tree selection, group felling, shelterwood cuttings and small clear cuts, resulting in a range of cutting intensities and gap sizes.In 2005, spruce seedling establishment as well as growth variables of the tallest seedlings were registered in circular plots of 50 m2 in the different treatments, and soil thickness and moisture class were registered in the same plots. Samples of seedling needles were tested for nitrogen content. Light levels (diffuse, direct and total radiation) below the canopy were measured for each circular plot using hemispherical photography.A covariance analysis with light level as the continuous variable was used to test whether seedling establishment or growth was dependent of soil depth, moisture class or light levels. Diffuse light values corresponded best with seedling growth. The levels of diffuse light in the partial cuttings varied from 19 to 30 % of above canopy values, with the shelterwoods and the group fellings having the highest levels. Still, the clear cuts had light levels more than twice as high as the shelterwoods.The number of spruce regeneration varied substantially between plots with the same harvesting treatment. Seedling numbers were dependent on soil conditions, and were highest on sites with good moisture conditions and soil thickness 20 cm. The covariance analysis did not give a significant effect of light values on spruce seedling number, but there was a tendency to better regeneration at medium light levels.However, the growth of the seedlings was strongly dependent on light levels, with taller leader length and total growth as well as a higher number of annual shoots under good light conditions.Soil depth was insignificant for seedling growth, but moisture class affected annual height growth. Nitrogen concentration in seedling needles was positively correlated with light conditions and negatively with stand density in the vicinity of the seedling, which indicates that the positive effect of large gaps on seedling growth may be caused by decreased competition for nutrients as well as increased radiation levels. Soil depth did not influence the nitrogen concentration.
Authors
Mauro Bernabei Peder GjerdrumAbstract
NOAA Paleoclimatology betjener et World Data Center for Paleoclimatology, herunder en database for årringobservasjoner. Vi har ønsket å gjøre våre observasjoner av barlind fra det italienske Alpe-området allment tilgjengelige gjennom registrering i denne databasen: http://www.ncdc.noaa.gov/paleo/paleo.html Velg Tree-Ring og søk blant tilgjengelige data.