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
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
There is a high correlation between methods for dynamic modulus of elasticity (MOEdyn) and static modulus of elasticity (MOEstat). MOEdyn methods have been found sensitive to detect early stages of decay and may be seen as an option for non-destructive wood durability testing.As the MOEstat measurements do not change after reaching the fibre saturation point, the uncorrected MOEdyn data from ultrasonic pulse excitation method provides increasin values after fibre saturation. This is due to the effect of free water in the cell lumen on ultrasonic waves. The aim of this study was to make a moisture calibration for the MOEdyn ultrasonic pulse excitation method using Scots pine (Pinus sylvestris L.) sapwood samples.MOE was measured at five different moisture levels. Three different MOE test methods were used: MOEdyn using ultrasound and vibration excitation and the traditional MOEstat. Sound Scots pine sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated, using untreated sapwood samples as control.In this study a correction value (\"k\") was calculated based on data from different moisture levels for water saturated samples using four different wood treatments and control. By measuring MOEdyn ultrasonic at wood moisture contents just below fibre saturation point, a minor effect of incipient water accumulation in the wood matrix was detected.Wood treatments influence the \"k\" value, and a \"k\" value needs to be calculated for all wood treatments when measuring MOEdyn ultrasound above fibre saturation. All the three MOE test methods in this study are applicable for all wood moisture levels as long as a \"k\" value is calculated for MOEdyn ultrasound above fibre saturation.
Abstract
No abstract has been registered
Authors
Anna Holefors Anne Katrine Ree Rosnes Lars Morten Opseth Carl Gunnar Fossdal Jorunn Elisabeth OlsenAbstract
No abstract has been registered
Abstract
We describe the cloning and characterization of a single copy gene from Trichoderma atroviride P1 encoding a novel 30 kDa chitinase, Ech30. Ech30 is a family 18 chitinase showing low sequence similarity to other Trichoderma chitinases. Real-time quantitative RT-PCR studies revealed that expression of the ech30 gene was induced by the presence of Botrytis cinerea in plate confrontation assays, but hardly by chitin in liquid cultures. Studies of Ech30 purified from an Escherichia coli strain overexpressing the ech30 gene devoid of the leader sequence and a predicted intron, showed that the gene encodes an active chitinase, which, as expected for family 18 chitinases, is inhibited by allosamidin.
Authors
Stig Strandli GezeliusAbstract
No abstract has been registered
Abstract
No abstract has been registered
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
No abstract has been registered
Abstract
In Norway exterior wood structures have traditionally nearly exclusively been made of treated and untreated Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.). In recent years there has been a tendency that other tree species, like various domestic hardwoods and imported species have been used in exterior above ground applications, often unfinished. For several wood species, especially hardwoods, information regarding the durability in use class 3 is lacking. The test procedures prescribed in the European standards, both laboratory and field tests, have some weaknesses regarding to natural durability testing. Hence, some new methods for accelerated above ground testing have been put forward. The main objectives of this project are to evaluate natural durability of Norwegian wood species for above ground applications, and to study various methods for assessing decay in wood. This paper presents the material and methods used in the project, and report the results from double layer tests after one year of exposure. No decay was detected, but almost all wood species were considerably discoloured. Thuja (Norw.), Thuja (Am.), Intsia and Tectona had the least amount of discolouration. The Norwegian softwood species had generally less discolouration than the Norwegian hardwood species. CCA and Cu preservative impregnated and FA modified Pinus sylvestris sapwood had more cracks than most of the untreated wood species. Moreover, some of the Picea abies qualities and Pinus sylvestris sapwood samples had substantial amounts of cracks.