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.
1999
Forfattere
Carl Gunnar FossdalSammendrag
Plants are exposed to a great number of microorganisms under natural conditions. Pathogenic fungi and oomycetes are the main factors contributing to plant diseases, thus further understanding of plant-pathogen interactions may provide information leading to new strategies for reducing the damage caused by these pathogens on economically important trees and crops. Active plant-responses to microorganisms differ with respect to the degree of responses and with respect to the outcome of the interaction. In response to pathogens, active plant-defenses can be induced. Both local and systemic plant defense-response may be induced by pathogens. This thesis present indications of both local and systemic host responses at the molecular and cellular levels, using the conifer Norway spruce as a model host to study plan-pathogen interactions. Norway spruce seedlings were infected separately with the pathogenic fungi Heterobasidion annosum and Ceratocystis polonica, the pathogenic oomycete Pythium dimorphum and the ectomycorrhizal fungus Laccaria bicolor, to study the local and systemic effects of the infections at the cellular and molecular level. Increased levels of lignification was seen within 2 to 4 days in response to the pathogens, and indications of cytoplasmic translocations were also observed as a response to hyphae invading the root. Initially, a defense related plant peroxidase cDNA SPI2 (spruce pathogen induced 2) from Norway spruce roots was isolated and sequenced and found to encode a predicted 34kD SPI2 protein. The 34kD SPI2 protein was detected both in the root and shoot of Norway spruce seedlings, and accumulated as a local response to infection with the pathogenic oomycete Pythium dimorphum. In addition, two 38kD and 39kD SPI2 related proteins were detected in roots only after infection. Interestingly, increase levels of the 39kD SPI2 related protein was also detected in shoots of infected seedlings as a systemic response to infection. The putative plant defensin SPI1 (spruce pathogen induced 1) from Norway spruce has been proposed a role in the defense against pathogenic fungi and oomycetes. Here the predicted 5kD SPI1 protein was detected in Norway spruce seedlings and found to accumulate in roots during development. Notably, the putative plant defensin SPI1 lined the wall of cortical root cells, and in roots invaded by P. dimorphum the SPI1 protein was found associated with the invading hyphae. This supports the hypothesis that SPI1 has a role in the defense against pathogenic oomycetes and fungi. The possible protective role of prior colonization by the ectomycorrhizal fungus on later challenge with the pathogen C. polonica, previously known to be vectored to the tree stem by bark beetles, was also examined. Surprisingly, C. polonica was able to invade also roots of both mycorrhizal and non-mycorrhizal seedlings. Not only induced or enhanced plant responses were observed, but also reduced levels of defense-related proteins were observed in the infected roots at the later stages of infection. Decreased levels of SPI1was detected within 96 hours after infection in response to the pathogens tested. Reduced levels of the corresponding transcript was also detected indicating a suppression of host responses by the pathogens. Increased proteolytic activity was detected in infected roots, and from the pathogens. Proteolytic degradation of host proteins by fungal secreted proteases may reduce the levels of potentially antimicrobial proteins enabling the pathogens to effectively invade the roots. Reduced levels of the SPI1 in roots, was found also in response to the ectomycorrhizal fungus L. bicolor. Reduced levels of the peroxidase isozymes at the later stages of the infections, was also observed. Thus, suppressor(s) may be produced by both the pathogens and by the ectomycorrhizal fungus during infection, reducing the host responses and contributing to successful colonization of the roots.
Forfattere
Per Holm Nygaard Torbjørn ØdegaardSammendrag
Vegetation data were collected in 1931, 1961 and 1991 from permanent plots in a boreo-nemoral forest 20 km north of Oslo in southern Norway. Major changes were found in the vegetation composition during 60 years. The main changes were a reduction in the frequency and frequency of joint occurrence of species like Calluna vulgaris, Vaccinium uliginosum, Trientalis europaea, Maianthemum bifolium, Melampyrum pratense, Cornus suecica, Andromeda polifolia, Eriophorum vaginatum, Vaccinium oxycoccus, Pleurozium schreberi, Hylocomium splendens, Ptilium crista-castrensis, Dicranum fuscescens and Ptilidium ciliare. The observed changes were interpreted as induced by internal processes e.g., a long-term change from paludified forest to mesic forest. In particular the growth of Picea abies seems in particular to be a main driving force. The dominance of Picea abies and Vaccinium myrtillus appears to have made the conditions more unfavourable to other species. A doubling of the living stem biomass of P.abies during the last 67 years shows that this old-growth forest has not reached a steady state. Species like Deschampsia flexuosa and Molinia caerulea did not increase in frequency as has been demonstrated in response to nitrogen deposition elsewhere in northern Europe. The results of this study indicate that protection from logging has promoted the reduction of species in the field layer and bottom layer. This study questions if monitoring of forest vegetation should be restricted to protected forests as is the practice in Scandinavia today. We recommend that areas with some kind of selective cutting are also used for monitoring of forest vegetation
Forfattere
M. Lavoie Peder GjerdrumSammendrag
The aim of this study has been to investigate the effects of high temperature drying on the equilibrium moisture content, to verify the presence of hysteresis and to screen the effects of high temperature on timber quality. Further, we wanted to utilise the laboratory kiln at Forestia Sokna in a pilot project, to learn more about the experimental possibilities connected to this equipment. The hypothesis was that the equilibrium moisture content will decrease as the drying temperature increase. Five series of twelve spruce wood samples each were prepared to verify this hypothesis: air-dried (green samples), moist samples for desorption and dry samples for adsorption for the ordinary-progressive (72 C) and for the high temperature kilns (115 C). The tension has been measured to compare the timber quality between ordinary-progressive and high temperature kilns. The conclusion is that there was too much stochastic noise to verify the initial hypothesis. Consequently it was impossible to confirm the presence of hysteresis. There are interesting observations to make in further research on how fast the equilibrium moisture content is reached according to the drying temperature. This experiment has been accomplished using Norway spruce, and further research should include Scots pine or other coniferous species.
Sammendrag
Potential response of forest soils to sulphur deposition in the Norwegian-Russian border area in the surroundings of the Pechenganikel smelters, the major sulphur emitters in the northern Europe, has been assessed with the PROFILE model. The release rate of base cations due to weathering range from 0.05 to 0.28 kmol(c)/ha/yr in the 0 - 50 cm soil layer, thus demonstrating the high sensitivity of the coarse and thin podzols studied. Calculated steady-state BC/Al values are significantly lower than the presumed critical value of 1, which indicate possible negative effect on vegetation through soil acidification. According to the model calculations future sulphur deposition have to be very low in order to stop the ongoing acidification and prevent vegetation damage. However, model assumptions, uncertainty in input data and critical chemical values applied implies that modelling results must be interpreted carefully
Forfattere
Svein Ola MoumSammendrag
The article presents a mapping system describing agricultural resources in scales ranging from 1:100.000 down to 1:300.000, with respect to a prototype covering an area of Nord-Gudbrandsdalen district. The maps cover all Norwegian land types grouped into 13 classes.Ancillary data is widely used and the area where new interpretation is needed was thus limited to dry land above the tree line. The land type of these areas was interpreted from Landsat TM images. Maps produced with this system offer a coherent overview of the landscape and land types for large areas. Land type statistics from these small-scale maps is only recommended when the claim of accuracy is low and statistical bias is acceptable. Use of the maps for regional and agricultural planning as well as for environmental impact assessment is discussed.
Forfattere
Svein SolbergSammendrag
On the local county monitoring plots located throughout Norway a reduction of crown density has been noted during 1988-97. The aim of this study was to determine whether this change could be attributed to normal effects from increased age on the plots.The dataset comprised around 580 plots and 27 000 single trees of Norway spruce, where each tree was provided with ten years of crown density measures. A two step approach was used, firstly to search for an expectancy for normal reduction of crown density by age derived from the dataset, and then to compare this with the actual reduction. The interpretation was somewhat complicated as the various results were tangled into each other.Highly significant correlations were found between crown density and age. The relationship indicated an annual reduction of crown density around 0.12%-units, however, the relationship varied both between years and between regions, and it was not possible to definitely determine whether the relationship was best described by linear or non-linear models.Of major importance here is that the relationship appeared to be influenced by the presence of stresses, which effects tended to be more severe in old stands. Based on this it seems questionable whether an expectancy for normal ageing can be properly defined. However, in the present study it could still be definitely determined that the mean crown density change of -0.41%-units annually was too negative to be attributed to normal ageing, as it was clearly below all the suggested expectancies from the various models.This suggests that the amount of stress in the period under study has been higher than normal, and this encourages the search for causal agents in further studies. Changes in silviculture may have had some influence.The results were valid for most of Norway, with the exception of western and northern regions. Crown density assessments are subjective, which may possibly give erroneous time trends, however, it is argued that this is less likely to be of major importance in the present data.
Forfattere
Petter NilsenSammendrag
Litteraturgjennomgangen gir en oversikt over resultatene fra de ulike typene av gjødslingsforsøk i skog på fastmark i Norge. Som andre steder i den boreale sone er nitrogen (N) gjennomgående det mest vekstbegrensende næringsstoffet i skog. Til tross for vedvarende N deposisjon i flere 10 år er det lite som tyder på at den vekststimulerende effekten av N gjødsling i skog er forandret. I eldre skog vil tilførsel av 150 kg N pr. ha i gjennomsnitt gi en tilvekstøkning på 1-2 m3 tømmer pr. ha og år i en 6-8 års periode. Slik gjødsling er i dag den mest rentable investeringen som kan gjøres i skogbrukets primærproduksjon. Også i ung skog (hogstklasse II og III) vil N gjødsling stort sett gi meget god vekstrespons. I granbestand kan man i enkelte tilfeller oppnå en tilleggseffekt av tilførsel av 20-40 kg fosfor (P) og 30-50 kg kalium (K) pr. ha. Det finnes indikasjoner fra Sørlandet om at P gitt alene i enkelte tilfeller kan føre til en økt høydetilvekst. Dette er foreløpig ikke godt nok klarlagt.Startgjødsling med P eller NPK (50-100 gram superfosfat eller fullgjødsel) har vist seg å gi meget gode resultater på veksthemningsmark på ytre strøk av Vestlandet, både på plantenes overlevelse og tilvekst. Nylig vedtatte standarder for skogbruket tilsier imidlertid at snaue områder med røsslyngmark ikke skal tilplantes, og dette er ofte den mest utpregede veksthemningsmarka. I andre deler av landet, både Østlandet og nordpå er det ikke funnet positive effekter i nevneverdig grad ved bruk av ulike typer startgjødsling. Dette tiltaket anbefales derfor ikke brukt i disse delene av landet. Lekkasje av nitrat kan være en viktig bieffekt av gjødsling. Det er bare ved høye akkumulerte doser etter gjentatte gjødslinger med N at nitratlekkasje er registrert i noe omfang. En generelt god vekstrespons hos trærne på N gjødsling vil medvirke til at nitratavrenningen vil være lav ved praktisk gjødsling. Faren for en forbigående økt nitratavrenning kan være større i områder med høy N deposisjon. Vegetasjonsendringer av betydning er også bare registrert i forbindelse med meget store doser N. Gjødsling i områder med høy N deposisjon kan muligens forsterke vegetasjonsendringer som kan tenkes indusert over lang tid under slike forhold. Andre sentrale prosesser i skogøkosystemet (immobilisering, mineralisering, gasstap) har også vist seg å være relativt lite påvirket ved de gjødseldoser som anbefales i praksis. Når det gjelder mottiltak mot forsuring av skog så anbefales det ikke å kalke skog i stor skala. Årsaken til dette er bl. annet manglende eller negativ tilvekstrespons hos trær, de økonomiske uttellingene og faren for vegetasjons-endringer. Det anbefales heller ikke å sette inn forebyggende vitaliseringsgjødsling (N-fri gjødsling) i skog.Dersom næringsmangel skulle opptre lokalt bør denne elimineres ved bruk av riktig tilpasset gjødsel og dolomitt. På grunn av liten interesse for skoggjødsling i det praktiske skogbruket, vil sannsynligvis framtidig forskningsvirksomhet konsentreres om næringssirkulasjon, næringsbalanse og N metning, og i mindre grad de praktiske aspektene ved skoggjødsling. I Ottadalen er det påvist bor (B) mangel i ung granskog i enkelte områder og behovet for gjødslingsforsøk vil her være tilstede for å kunne gi best mulig råd for forebyggende gjødsling til det praktiske skogbruket.
Rapport/avhandling – Lønnsomheten av juletrehogst i hogstklasse II
Sveinung Nersten, Morten Hedegart
Forfattere
Sveinung Nersten Morten HedegartSammendrag
Harvesting christmas trees from regenerations in cutting class II - young growth stands - has been practiced for a long time. It is often the forest owner himself who performs the cutting, transportation of the trees to the market place, and the actual marketing. In some cases the forest owner sells the trees to a wholesale or a market dealer. The new aspect of the production model described in the this report - the Birkenes model - is that the trees in advance are selected and marked by competent persons. Information is then given to the wholesale dealer on the number of trees that has been marked at each site, and the dealer reports on the number of trees he wants to buy. The forest owner cuts the relevant number of trees and transports them to the roadside. The trees are controlled by the dealer when loading. Some trees may be discarded, but usually not many. The scope of the present study is to look into the profitability of cutting christmas trees in cutting class II by: Estimating possible reductions in the expectation value when trees are removed from a regeneration. Record time consumption and costs, and calculate net values connected with harvesting christmas trees by various methods and under various conditions. Look into the profitability of establishing more dense plantations for later removal of surplus plants as christmas trees. The field work consists of two parts, surveying of fields for christmas tree harvesting, and recording of the labour used for cutting and transporting the trees to the roadside. The factors affecting the expectation value are the number of trees left after harvesting, and effects on age and quality. The recordings and calculations show that it is primarily the reduction of the number of trees left in the regeneration that affects the expectation value negatively. The costs of manual labour are assumed to be NOK 2 per minute and the costs of machines NOK 3 per minute. The cost connected to marking and delivery of the christmas trees are set to NOK 7 per tree. A rate of interest of 2.5 percent is applied in the expectation value calculations. The sales price per tree to the dealer is set to NOK 45 per tree. The cost of harvesting as well as net price are estimated per tree. The cost of hauling the trees manually depends strongly on the person doing the job, and on hauling distance. If tractor transport is applied, the hauling distance can be considerably increased. Net price per tree increases with increasing number of trees before harvesting and for lower site classes, and decreases a bit with increasing number of trees harvested. For site class G14, initial number of trees 1,600 per ha, number of trees harvested 400 per ha, and hauling distance 50 m, the net price per tree is NOK 15.10. Under the same conditions, except that the hauling distance is 500 m, the net price is NOK 3.
Forfattere
Knut SolbraaSammendrag
Undersøkelsene tok sikte på å undersøke virkningen av barklag i forskjellige tykkelser på eldre furutrær og av et 5 cm dekklag av råslam på unge planter, i begge tilfeller på næringsfattig, sedimentær jord. Slameffekten sammenlignes med effekten av fullgjødsel D. Registreringene dekker 19-24 vekstsesonger. Resultatene viste at det kan legges ut opptil 80 cm bark uten å skade trærne. Barklag med tykkelser på 40-80 cm ga størst vekstøkning, som startet 6-7 år etter utlegging. Det var i en periode tre ganger så rask vekst i barkruter som i ruten uten bark. Råslam ble brukt for å bedre vekstforholdene etter skogbrann på næringsfattig mark og ga en vedvarende rask vekst gjennom registreringsperioden. Plantehøyden økte 2,5 ganger i forhold til ubehandlet rute. Til tross for at vekstforholdene opprinnelig var dårligere, var veksten større i slamruten enn i ruter som var intensivt gjødslet med fullgjødsel i perioden 1983-1988. Det var liten påvirkning fra slamlaget på konsentrasjonen av andre grunnstoffer enn makronæringsstoffer i plantenes nåler, og det skjedde liten anrikning i utfellingslaget under slamdekningen. Gjødsling med fullgjødsel økte elgbeitingen på forsøksplanter.
Sammendrag
Within the framework of the Programme for Terrestrial Monitoring (TOV), soil water has been collected from four monitoring plots in 1998 (Fig. 1). Three of the plots are located in birch forest, and one (Solhomfjell) is located in spruce forest. Height above sea level, annual precipitation and growing season temperature show significant variation between plots. Bilberry or bilberry-crowberry are the main vegetation types.Results from 1998 are reported and compared with results from preceeding years. On all plots soil water has been sampled from three soil depths (except Gutulia); the organic layer, the upper and the lower part of the mineral soil (5, 15 and 40 cm soil depth, respectively).The chemical composition of the soil water depends largely on the chemistry of the soil and the amount and quality of the precipitation. The soil chemistry in humic layer and from 5-15 cm depth in the mineral soil is shown in Table 1 and 2, respectively. The concentrations of some of the main elements in soil water from 1998 are shown in Table 3.The pH in soil water increases usually with soil depth. The annual variations in pH from 1991 to 1998, are shown in Figure 2. In Lund there has been a slight decrease in pH in these years, although continous measurements are lacking at 5 cm. Figure 2 also show the same tendencies for Ca2 as for pH in Lund.There is greater annual variation in concentrations of Ca2 and other element in the humic layer than mineral layers. Also other nutrients, such as Mg2 and K, were found with the highest concentrations in the organic soil layer and decreased with increasing soil depth.The concentrations of SO42- were in 1998 below 1 mg/l and only with a few exceptions larger than 1 from 1991 to 1998 (Fig.3). SO42- generally show a decreasing trend in that period. Total Al were lower than 1.0 mg/l for most of the samples. The amount of inorganic Al, which is known to be toxic for plant roots at certain concentrations was first time measuered on the plots in 1998. However, the values were small, well below 1.0 mg/l.That were simular to results from The Forest Monitoring Programme in Norway (OPS) which shows that the concentration of inorganic Al varies between plots and soil depths. Here, however, at some plots there were concentrations of inorganic Al up to 2.0-3.4 mg/l. Results from experiments with Norway spruce seedlings (Picea abies) in nutrient solution show slight decline of the roots at concentrations of unorganic Al at 2.0 mg/l (Eldhuset pers. comm.). This may suggest that even if the concentration of unorganic Al at the TOV-plots were below 1.0 mg/l, there could be periods with higher concentrations that could have effected the plant roots.The concentration of Cl- varied greatly between the plots (Fig. 3), due to the deposition of sea salts. The plot in Gutulia had minimal variation between years and Cl- concentrations were always below 1.0 mg/l. In contrast, the plot in Lund had both the highest concentrations of Cl- and the highest seasonal and annual variation. The between layer differences were usually small each year.Analyses of precipitation show that Lund has the highest supply of acidity, Mg2, SO42-, Na and Cl- of all plots (Trseth og Man 1997). Even if the supply of N also is highest in Lund, soil water from all plots has shown low amounts of N (mostly at detection levels for NH4 and NO3, Table 3) throughout the monitoring period. This may be explained by the low content of plant available nitrogen in Norwegian soils, and plant uptake would minimize any leaching.At present these results give no indication of forest decline in Lund despite decreasing pH and concentration of Ca2 in the soil water. At present it is not possible to confirm that the changes observed in pH and Ca2 are caused by long range air pollution. They may also be due to natural variations in the chemical composition of soil water. It is recommended to continue the soil water monitoring.