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.
2013
Forfattere
Jan Čermák Pavel Cudlin Roman Gebauer Isabella Børja Milena Martinková Zdeněk Stanĕk Jan Koller Jindřich Neruda Nadezhda NadezhdinaSammendrag
Estimates of root absorption magnitude are needed for the balanced management of forest ecosystems, but no methods able to work on the whole tree and stand level were available. Modified earth impedance method was developed recently and here it was tested, by comparing the results with those obtained by combination of several classical methods. Methods We used direct (soil cores, scanning and microscopy) and indirect (sap flow patterns and modified earth impedance) methods in an attempt to estimate the absorptive root area indexes (RAI) at two sites of about 25 and 40-years-old Norway spruce. We considered the geometric surfaces of all scanned fine roots to be equal to the fine root absorptive area (RAIscan). To estimate the potentially physically permeable area of fine roots, we microscopically evaluated the point of secondary xylem appearance and calculated the geometric area of root portions with primary structure (RAImicro). We termed the area of electrically conductive root surface as the active (ion) absorptive area (RAImei) and measured its extent by the modified earth impedance (MEI) method. Results The highest values for absorptive root areas at the two experimental sites we obtained with the scanning method (RAIscan was considered to be 100%), followed by the RAImicro (51%) and RAImei (32%). RAImei reached about 2/3 of RAImicro. The surface area of the ectomycorrhizal hyphae was an order of magnitude larger than that of all fine roots, but the MEI did not measure such increase. Conclusions We showed that the absorptive root area, indirectly estimated by the MEI, provides consistent results that approach the values obtained for fine roots with a primary structure estimated by traditional direct methods. The similar range of the values for the absorptive root surface area obtained by microscopy and by the MEI method indicates that this method is feasible and that it could be used to determine the extent of active absorptive root surface areas in forests.
Forfattere
Igor A. Yakovlev Ari Hietala Pierre-Emmanuel Courty Taina Lundell Halvor Solheim Carl Gunnar FossdalSammendrag
The pathogenic white-rot basidiomycete Heterobasidion irregulare is able to remove lignin and hemicellulose prior to cellulose during the colonization of root and stem xylem of conifer and broadleaf trees. We identified and followed the regulation of expression of genes belonging to families encoding ligninolytic enzymes. In comparison with typical white-rot fungi, the H. irregulare genome has exclusively the short-manganese peroxidase type encoding genes (6 short-MnPs) and thereby a slight contraction in the pool of class II heme-containing peroxidases, but an expansion of the MCO laccases with 17 gene models. Furthermore, the genome shows a versatile set of other oxidoreductase genes putatively involved in lignin oxidation and conversion, including 5 glyoxal oxidases, 19 quinone-oxidoreductases and 12 aryl-alcohol oxidases. Their genetic multiplicity and gene-specific regulation patterns on cultures based on defined lignin, cellulose or Norway spruce lignocellulose substrates suggest divergent specificities and physiological roles for these enzymes. While the short-MnP encoding genes showed similar transcript levels upon fungal growth on heartwood and reaction zone (RZ), a xylem defense tissue rich in phenolic compounds unique to trees, a subset of laccases showed higher gene expression in the RZ cultures. In contrast, other oxidoreductases depending on initial MnP activity showed generally lower transcript levels on RZ than on heartwood. These data suggest that the rate of fungal oxidative conversion of xylem lignin differs between spruce RZ and heartwood. It is conceivable that in RZ part of the oxidoreductase activities of laccases are related to the detoxification of phenolic compounds involved in host-defense. Expression of the several short-MnP enzymes indicated an important role for these enzymes in effective delignification of wood by H. irregulare.
Sammendrag
This study combines tree-ring and charcoal data to explore possible drivers of the charcoal record and its spatial variation in a boreal Norwegian forest landscape. Peat and mineral soil samples were collected in a multiple site sampling approach and the amount of charcoal in the peat is related to fire history, Holocene climate variation, major shifts in the vegetation composition, and fuel availability. Dendrochronologic dating was used to reveal the fire history over the last 600 years with spatial and temporal accuracy, and AMS radiocarbon dating of 20 peat columns and their charcoal records from four peatlands was used to elucidate the fire history over the Holocene. The average amount of charcoal was about 2.5 times higher in the mineral soil than in the peat (270 versus 100 g/m², respectively), and there were considerable between- and within-site variations. There was no relationship between the age of a given peatland and its content of charcoal, nor between the amount of charcoal in a given peatland and in the neighboring mineral soil. Although most of the charcoal mass in the peatlands was found in parts of the peat columns originating from relatively warm climatic periods and from the period before the local establishment of Norway spruce (Picea abies), charcoal accumulation rates (per 1000 yr) were higher during cold climatic periods and similar before and after spruce establishment. Recent fires showed up to a low degree in the peat columns. On fine spatial scales (1–10 m), fuel quality and distribution together with fire behaviour throughout millennia are likely to be responsible for variations in the charcoal record. On the landscape scale (100–1000 m), the charcoal records were site-specifically idiosyncratic, presumably due to topography, distribution of fire breaks and fuel types, and human land use, coupled with long-term variations inherent in these factors.
Sammendrag
Shoot dieback disease of European ash caused by the ascomycete Hymenoscyphus pseudoalbidus threatens ash on a continental scale. A spore sampler placed in a diseased ash forest in Southern Norway, coupled with microscopy and DNA-based fungal species-specific real-time PCR assays, was employed to profile diurnal and within-season variation in infection pressure by ascospores of H. pseudoalbidus and the potentially co-existing non-pathogenic Hymenoscyphusalbidus. Hymenoscyphus pseudoalbidus was found to be predominant in the stand. Massive simultaneous liberation, by active discharge of pathogen ascospores in the morning, peaked in mid-Jul. to mid-Aug. Accumulation of pathogen DNA on leaflets of current-year leaves reached a high level plateau phase before appearance of autumn coloration, suggesting that pathogen establishment in leaves is terminated before the onset of leaf senescence.
Forfattere
Ingebjørg Helena Nymo Jacques Godfroid Kjetil Åsbakk Anett Kristin Larsen Carlos G Das Neves Rolf Rødven Morten TrylandSammendrag
Det er ikke registrert sammendrag
Sammendrag
The quality of surface water and groundwater is closely related to flow paths in the vadose zone. Therefore, dye tracer studies are often carried out to visualise flow patterns in soils. These experiments provide images of stained soil profiles and their evaluation demands knowledge in hydrology as well as in image analysis and statistics. The classical analysis consists of image classification in stained and non-stained parts and calculation of the dye coverage (i.e. the proportion of staining). The variation of this quantity with depth is interpreted to identify dominant flow types. While some feature extraction from images of dye-stained profiles is necessary, restricting the analysis to the dye coverage alone might miss important information. In our study we propose to use several index functions to extract different (ideally complementary) features. We associate each image row with a feature vector (i.e. a certain number of image function values) and use these features to cluster the image rows to identify similar image areas. Because images of stained profiles might have different reasonable clusterings, we calculate multiple consensus clusterings. Experts can explore these different solutions and base their interpretation of predominant flow type on quantitative (objective) criteria.
Forfattere
Tino Schott Lauri Teemu Kapari Snorre Hagen Ole Petter Laksforsmo Vindstad Jane Uhd Jepsen Rolf Anker ImsSammendrag
Outbreaks of geometrid defoliators in subarctic birch forest in Fennoscandia often occur at high altitude in a distinct zone along the tree line. At the same time, moth larvae may not have an impact on the forest at lower altitude. Directly adjacent outbreak and nonoutbreak areas offer unique opportunities for studying the underlying mechanisms of outbreaks. Within two altitudinal gradients in coastal northern Norway, we investigated whether altitudinal outbreaks might be caused by release from pupal predation by ground-dwelling invertebrates such as harvestmen (Opiliones), spiders (Araneae), rove beetles (Coleoptera: Staphylinidae), carabid beetles (Coleoptera: Carabidae), and other beetles (Coleoptera). We predicted a consistently higher abundance of such generalist predators at low versus high altitudes. Our results did not support this prediction. There was no consistent altitudinal variation in the abundance of predators that could be related to zonal moth outbreaks in the birch forest slopes. In addition, none of the predator groups investigated showed any numerical response to a distinct outbreak of winter moth that took place during the course of the study. Consequently, localised moth outbreaks at the altitudinal tree line in northern Norway cannot be explained by the release from pupal predation by the predator groups examined here.
Sammendrag
The relative volume growth effects of thinning after whole-tree harvesting (WTH) compared to a conventional stem-only harvest (CH) in young stands of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) were analyzed, using a series of four pine and four spruce field experiments. The series was established in the years 1972–1977, and thinning was performed only once. Results are shown periodically and cumulatively. All sites were included for 20 (19) years in pine and 25 years in spruce. The total experimental period varied between 19 and 35 years for individual sites. Four models assuming additive or multiplicative effects gave only slightly varying results. The inclusion of standing volume after thinning as a covariate was effective in spruce independent of whether the covariate was treated as multiplicative or additive. A logarithmic model with a multiplicative effect of the covariate was preferred in further presentations. Results for pine stands after 20 years indicated a nonsignificant loss of 5% with confidence limits (p = 0.05) of ±6–7%, while the spruce stands showed a significant growth loss of 11% with confidence limits of ±4–5% after 25 years. The difference between the species in relative growth effects was significant, and amounted to 8% for a cumulative 20-year period. No indications of trends in response were found during a 20-year period in pine and a 25-year period in spruce. An analysis of growth effects in the first years showed that basal area increment in spruce was significantly reduced already in the first growing season after thinning.
Sammendrag
1. Whether plant competition grows stronger or weaker across a soil fertility gradient is an area of great debate in plant ecology. We examined the effects of competition and soil fertility and their interaction on growth rates of the four dominant tree species in the sub-boreal spruce forest of British Columbia. 2. We tested separate soil nutrient and moisture indices and found much stronger support for models that included the nutrient index as a measure of soil fertility. 3. Competition, soil fertility and their interaction affected radial growth rates for all species. 4. Each species supported a different alternate hypothesis for how competitive interactions changed with soil fertility and whether competition intensity was stronger or weaker overall as soil fertility increased depended on the context, specifically, species, neighbourhood composition and type of competition (shading vs. crowding). 5. The four species varied slightly in their growth response to soil fertility. 6. Individual species had some large variations in the shapes of their negative relationships between shading, crowding and tree growth, with one species experiencing no net negative effects of crowding at low soil fertility. 7. Goodness-of-fit was not substantially increased by models including competition–soil fertility interactions for any species. Tree size, soil fertility, shading and crowding predicted most of the variation in tree growth rates in the sub-boreal spruce forest. 8. Synthesis. The intensity of competition among trees across a fertility gradient was species- and context-specific and more complicated than that predicted by any one of the dominant existing theories in plant ecology.
Sammendrag
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