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.
2009
Authors
Kjersti Holt HanssenAbstract
We studied the growth of Norway spruce and Scots pine seedlings in the understory, using three sites with selective cutting and group fellings in SE Norway. Seedlings were planted in plots with and without trenching in gaps of four different sizes, ranging from 20 m2 to 500 m2 and giving light levels from around 20 to 75 % of open sky. After tree years seedlings were dug up and measured. Vegetation cover was also registered. Growth of both species was positively and significantly correlated with increasing gap size. This applied for height, diameter, shoot volume, needle length and needle number as well as total dry weight. However, trenching also had a clear and significant positive effect on the same growth parameters. The growth of some weed species, especially wavy hair-grass (Deschampsia flexuosa) also increased significantly with both gap size and trenching. The results show that competition for both light and below-ground resources matters for understory seedling growth under the studied conditions.
Abstract
European ash (Fraxinus excelsior), also known as common ash, occurs naturally inland in lower areas of southeastern Norway and along the southern coast of the country. It is important both as a forest and ornamental tree. During the last decade, dieback has become a disastrous disease on F. excelsior in many European countries. The anamorphic fungus Chalara fraxinea T. Kowalski (1), described for the first time from dying ash trees in Poland, is now considered the cause of ash dieback (2). In May of 2008, C. fraxinea was isolated from 1.5 m high diseased F. excelsior in a nursery in Østfold County in southeastern Norway. Symptoms included wilting, necrotic lesions around leaf scars and side branches, and discoloration of the wood. From symptomatic branches, small pieces (approximately 1 cm3) were excised in the transition area between healthy and discolored wood. After surface sterilization (10 s in 70% ethanol + 90 s in NaOCl), the pieces were air dried for 1 min in a safety cabinet, cut into smaller pieces, and placed on media. The fungus was isolated on potato dextrose agar (PDA) and water agar (WA). On PDA, the cultures were tomentose, light orange, and grew slowly (21 mm mean colony diameter after 2 weeks at room temperature). Typical morphological features of C. fraxinea developed in culture. Brownish phialides (14.8 to 30.0 [19.5] × 2.5 to 5.0 [4.1] μm, n = 50) first appeared in the center of the colonies on the agar plugs that had been transferred. The agar plugs were 21 days old when phialides were observed. Abundant sporulation occurred 3 days later. Conidia (phialospores) extruded apically from the phialides and formed droplets. Conidia measured 2.1 to 4.0 (3.0) × 1.4 to 1.9 (1.7) μm (n = 50). The first-formed conidia from each phialide were different in size and shape from the rest by being longer (6 μm, n = 10) and more narrow in the end that first appeared at the opening of the phialide. Internal transcribed spacer sequencing confirmed that the morphological identification was correct (Accession No. EU848544 in GenBank). A pathogenicity test was carried out in June of 2008 by carefully removing one leaf per plant on 10 to 25 cm high F. excelsior trees (18 trees) and placing agar plugs from a 31-day-old C. fraxinea culture (isolate number 10636) on the leaf scars and covering with Parafilm. After 46 days, isolations were carried out as described above from discolored wood that had developed underneath necrotic lesions in the bark and subsequently caused wilting of leaves. All the inoculated plants showed symptoms, and C. fraxinea was successfully reisolated. No symptoms were seen on uninoculated control plants (eight trees) that had received the same treatment except that sterile PDA agar plugs had been used.
Authors
Jarl-Gunnar Salin Peder GjerdrumAbstract
Wooden poles are frequently used for power and telecommunication lines. After creosote preservation the durability is secured for many decades. This study is related to a Norwegian plant where such poles are produced using Scots pine. Prior to the preservation process the poles have to be dried to a moisture content below the fibre saturation point everywhere in the pole. This is done outdoors in open stacks of poles, i.e. as air-drying. A problem is caused by the difficulties to determine when the target moisture content has been reached. The inventory of drying poles represents considerable value in a company\"s balance sheet and risk of downgrading. Knowledge of drying times during the annual seasons has been insufficient, and no efficient method is known for accurately observing the MC through the various parts of the poles.....
Abstract
Evaluation of climate change consequences and national carbon reporting such as under the Kyoto protocol require long-term monitoring of carbon fluxes. We report on an ongoing project aimed at a national-level assessment of the terrestrial carbon sequestration potential under present conditions and under various climate and land use change scenarios, in particular in terms of their temperature effect. We develop empirical models for national soil carbon stock assessment and evaluate process-based soil carbon models for prediction of future carbon dynamics.....
Abstract
The CO2 uptake of the terrestrial biosphere (Gross Primary Productivity, GPP) plays a key role in the global carbon balance. This carbon flux cannot be determined directly on a global scale. Yet, the remotely sensed Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) is a valuable proxy for GPP. This study aims at characterizing global FAPAR dynamics on different temporal scales and extracting corresponding spatial structures. The time series were analyzed to uncover the presence and extent of trends, and to identify quasi-oscillatory patterns from intra- to interannual time scales....
Abstract
In high-latitude areas, landscapes with flat or moderate relief areas usually contain lakes and mires. The identification of flowpaths in such areas is a difficult issue. The increasing availability of high resolution topography from airborne Lidar measurements offers new opportunities for automatic or semi-automatic channel extraction from DEMs in small watersheds, substantially outperforming the hydrographic network in conventional digital maps....
Abstract
Stream flow observations from a geographical region are known to often exhibit strong common behavior. In order to assess the temporal evolution of the complexity of stream flow time series from all over Europe, we employ the recently developed Linear Variance Decay dimension density (δLV D). It is estimated as the parameter of an exponential decay function fitted to the remaining variances of the eigenvalues of a covariance matrix. Scaling between zero and one, δLV D can be interpreted as a measure of the proportion of linear independent components in a multivariate record.....
Authors
Tor Myking Per Arild Aarrestad John Derome Vegar Bakkestuen Jarle Werner Bjerke Michael L. Gytarsky Ludmila Isaeva Rodion Karaban Vladimir Korotkov Martti Lindgren Antti-Jussi Lindroos Ingvald Røsberg Maija Salemaa Hans Tømmervik Natalya VassilievaAbstract
The effect of air pollution from the Petchenganickel industrial complex, northwestern part of the Kola Peninsula, on forest vegetation was studied by combining three dormant monitoring networks in Finland, Russia and Norway, comprising a total of 21 plots that were revisited in 2004. Chemical composition of precipitation was monitored during 2004–2005, and indicated continuing high deposition of heavy metals and SO2 in the border area. The cover of epiphytic lichens on the trunks of downy birch (Betula pubescens) and Scots pine (Pinus sylvestris) was severely affected by pollution, and there was also a consistent negative effect on the abundance and richness of lichens and bryophytes on the forest floor in a more limited area. The effects of pollution on crown condition and stand growth were weak or absent. This study is an important reference for evaluating the effects of the planned renovation of the smelter in Nikel.
Authors
Carl Gunnar Fossdal Igor A. Yakovlev Ari M. Hietala Halvor SolheimAbstract
To identify differentially expressed genes of the white-rot fungus Heterobasidion parviporum subtractive cDNA libraries were constructed using suppressive subtraction hybridization (SSH) technique with RNA extracted from an advanced stage of decay area and from colonization front next to the reaction zone of the stem of a mature Norway spruce trees. Besides cytochrome P450s and proteins with unknown function, the SSH libraries constructed contained genes involved in basic cellular processes, andcell wall degradation. To examine the role of selected candidate genes three trees, showing a variable degree of wood decay, were used for real-time RT-PCR profiling of candidate genes. In the decay transition areas the study revealed activity centers that showed remarkable similarity in the transcript profiles of monitored genes.
Authors
Nadeem Yaqoob Carl Gunnar Fossdal Jan Karlsson Benedicte Riber Albrectsen Halvor SolheimAbstract
Due to the great economic losses caused by the root and butt-rot pathogen Heterobasidion annosum, development of efficient control measures is warranted. H. annosum a necrotroph colonize the Norway spruce from inside and is responsible for 100s of millions of Euros losses annually. Considerable clonal variation has been recorded for Norway spruce in resistance towards H. annosum, but the defence mechanisms contributing to host resistance against both necrotrophic and biotrophic fungi remain poorly understood. The recent genome sequencing of Populus has made the genus a model to facilitate tree genetics. Genome-wide transcript profiling of Populus tremula upon pathogen attack will now be used, and homologues of Norway spruce genes to defence genes up-regulated in Populus will be identified. Two aspen clones (23 and 72) from the SwAsp collection (Luquez 2007) were used in the present study. Plants were propagated from tissue culture and kept in greenhouse under un-manipulated conditions. To study the host defence mechanisms, the rust (Melampsora magnusiana Wagner) and a bluestain fungus were used as a biotrophic and necrotrophic fungus respectively. Melampsora spores solution was applied to the underside of the leaf. To control for sectoriality six leaves were infected on each plant. To ensure high humidity and avoid cross contamination, plastic bags were wrapped around infected leaves. Leaves above infected leaves (10, 9, and 8) were harvested respectively 1, 3 and 14 days after inoculation. Initial results from microarray data indicate a clear separation between two Aspen clone (23 and 72) lines. For line 23 the response to biotroph and necrotroph seems to be similar. Whereas the response for line 72 is divergent for the treatments as they go in opposite direction. The controls show that there is an initial difference in the 2 lines (controls are separated). What are the genes that make biotrohic and necrotrophic treatment of 72 look so different will be worked out from microarray data. Differential expression of defense genes in biotrohic and necrotrophic treatment will be verified further with quantitative real time PCR. Chemical analysis of Aspen leaves gave less phenolic compounds as plants were kept in greenhouse. HPLC will be carried out after reaching some conclusion from microarray data analysis.