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
Sammendrag
The ground-based harvesting system consisting of a harvester and a forwarder is the dominant harvesting system in parts of the world, due to its high productivity. Both machines usually operate along extraction trails, and are equipped with cranes that can reach some distance from the extraction trail. In this work we optimize the layout of an extraction trail network by considering how terrain topography influences the cost of forwarding. Given the complexity of finding optimal machine trails for terrain transportation, traditional optimization methods might be limited due to the problem size. In this study, the optimization is done with a greedy constructive heuristic and a Greedy Randomized Adaptive Search Procedure (GRASP) metaheuristic, and the results of the two solution techniques are compared. Both the greedy heuristic and the GRASP metaheuristic were examined for a semi-random terrain and a smooth cone-shaped terrain, and provided useable extraction trail layouts in terms of how a forest machine operates on slopes. The objective value of the solution found by the GRASP metaheuristic was 5.6% better than the greedy heuristic in the semi-random terrain, and 2.3% better in the cone-shaped terrain. The result of this study showed that the GRASP metaheuristic is useful for finding feasible routes in the terrain, increasing efficiency. The method could be useful for planning feasible routes in the terrain, thereby increasing efficiency, or for acquiring a better estimate of the cost of terrain transport in price setting.
Forfattere
Heleen de Wit Anders Bryn Annika Hofgaard Jonas Karstensen Maria Malene Kvalevåg Glen Philip PetersSammendrag
Expanding high elevation and high latitude forest has contrasting climate feedbacks through carbon sequestration (cooling) and reduced surface reflectance (warming), which are yet poorly quantified. Here, we present an empirically-based projection of mountain birch forest expansion in south-central Norway under climate change and absence of land use. Climate effects of carbon sequestration and albedo change are compared using four emission metrics. Forest expansion was modeled for a projected 2.6 °C increase of summer temperature in 2100, with associated reduced snow cover. We find that the current (year 2000) forest line of the region is circa 100 m lower than its climatic potential due to land use history. In the future scenarios, forest cover increased from 12 to 27% between 2000 and 2100, resulting in a 59% increase in biomass carbon storage and an albedo change from 0.46 to 0.30. Forest expansion in 2100 was behind its climatic potential, forest migration rates being the primary limiting factor. In 2100, the warming caused by lower albedo from expanding forest was 10 to 17 times stronger than the cooling effect from carbon sequestration for all emission metrics considered. Reduced snow cover further exacerbated the net warming feedback. The warming effect is considerably stronger than previously reported for boreal forest cover, because of the typically low biomass density in mountain forests and the large changes in albedo of snow-covered tundra areas. The positive climate feedback of high latitude and high elevation expanding mountain forests with seasonal snow cover exceeds those of afforestation at lower elevation, and calls for further attention of both modelers and empiricists. The inclusion and upscaling of these climate feedbacks from mountain forests into global models is warranted to assess the potential global impacts.
Sammendrag
In Norway, water quality of small streams draining agricultural catchments has been monitored since 1993 by the Agricultural and Environmental Monitoring Program. This article attempted to examine the concentration levels, temporal dynamics and long-term trends (1993–2009 and 1996–2009) of Al, Fe, Cu, Mn and Zn in streams draining the catchment areas of Skuterud (4.5 km2) and Mørdre (6.8 km2), located in south-east Norway. In the Mørdre stream, Al, Fe, Cu, Mn and Zn all showed statistically significant downward trends (p<0.05), whilst in the Skuterud stream only Al and Fe showed statistically downward significance (p<0.05). The general declining trends of metal concentrations are most likely associated with reduction of acid rain deposition in southern Norway. In spite of this declining trends, over the 14–17 years of monitoring mean monthly concentrations of total Al (2.0–3.2 mg L−1), Fe (1.3–2.5 mg L−1) and Cu (8.9–26.1 µg L−1) in Skuterud and Mørdre streams, respectively exceeded the limits of the Norwegian Water Framework Directives, whereas the concentrations of Mn (22.3–40.8 µg L−1) and Zn (13.1–99.4 µg L−1) fell within the range of desired limits. Of the total water samples analysed from Skuterud (n=370) and Mørdre streams (n=255), nearly 80–84%, 70–87% and 79–96% were above the desired limits for Al (0.2 mg L−1), Fe (0.3 mg L−1) and Cu (3 µg L−1), respectively. In 2011, water analysis from drainage of forest soils (in Skuterud catchment) measured total Al: 0.42–0.79 mg L−1 and total Fe: 0.84–1.0 mg L−1 which were two to three folds greater than the desired limits. In general, weak correlations between runoff and concentrations of the metals in the streams were noted. Future research should focus on identifying the sources of Al, Fe and Cu and management interventions of elevated metal inputs to Skuterud and Mørdre streams.
Forfattere
Marit Jørgensen Kirsten Tørresen Marit Dyrhaug Ingrid Myrstad Jan Svendsen Tone Magnussen Anniken Førde A. DiTommasoSammendrag
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Forfattere
B. Dumont Anna Thorhallsdottir A. Faruggia Ann NorderhaugSammendrag
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Forfattere
Yngve RekdalSammendrag
Vegetasjonskart gjev eit bilete av den mosaikken av vegetasjonstypar som det naturlege plantedekket består av. Ein vegetasjonstype er ei karakteristisk samling planteartar som vil gå att på lokalitetar med like veksetilhøve. Ei oversikt over utbreiinga av vegetasjonstypar gjev oss på denne måten informasjon også om variasjonen i økologiske faktorar (klima, næring og vatn i jorda, snødekke og kulturpåverknad) i eit område. I tillegg kan kvar vegetasjonstype tilleggast eigenskapar med omsyn til ulik ressursutnytting og bruk (beite, slitestyrke for ferdsel, artsmangfald m.m.). I bygda Kvikne i Tynset kommune er det vegetasjonskartlagt eit areal på 146 km² på oppdrag frå Tynset kommune. Kartlegginga er gjort etter Skog og landskap sin instruks for vegetasjonskartlegging i M 1:20 000 - 50 000. Det er framstilt vegetasjonskart og 3 avleia temakart kring utmarksbeite for sau og storfe, og naturtypar viktige for biologisk mangfald. Kartområdet omfattar i første rekkje lisidene frå skoggrensa og ned til dyrka mark i bygda. 108 km² (74%) av kartområdet ligg under skoggrensa og 38 km² (26%) over. Høgaste punktet er Sætertangen 1200 moh. Dalbotnen i Kvikne ligg kring 550 moh. Lisidene stig bratt opp frå dalgangen over Kvikne. På austsida av dalen flatar det ut i eit roleg fjellandskap kring skoggrensa som går om lag 900 moh. På vestsida stig liene til om lag 1000 moh. før dei flater ut. Inn etter Ya er det vide landskapsformer med skogkledte lier og slake høer. Mellom Ya og Grytdalen er det eit meir småkupert landskap med mange nordvestsøraustgåande rabbar og smådalar.....
Sammendrag
A mountain pine beetle (MPB) epidemic is currently ravaging large areas of interior British Columbia (BC) with significant implications for ecosystem services including future timber supply and community economic stability. Information is needed on future stand dynamics in areas of impacted forests that are unlikely to be salvaged logged. Of greatest concern are stands dominated by lodgepole pine (>50% timber volume). Predicting how surviving trees in these areas respond and grow and the timing and species composition of natural regeneration ingress is of critical importance for multiple forest values. We undertook a retrospective study in the Flathead Valley of southeastern British Columbia where an intense MPB epidemic peaked in 1979–1980. Our objective was to gain insight into stand recovery and stand self-organization as influenced by species-specific growth responses of different sized secondary structure trees (individual seedling, sapling, sub-canopy and canopy trees surviving the epidemic) and post-beetle regeneration dynamics. MPB mortality rates, the percent of basal area killed by beetles, varied from 42% to 100% with most stands between 60% and 80%. In general, all surviving secondary structure released but the extent of growth release exhibited species variability. Release of surviving canopy lodgepole pine trees was often dramatic and greatest in stands with high total stand MPB mortality rates. Ingress of natural regeneration was slow in the first few years after MPB attack but there was a strong pulse of recruitment 10–20 years post disturbance which then slowed considerably. Nearly 30 years after the MPB attack, the stocking and composition of the understories have changed dramatically. Overall, the occurrence of the MPB epidemic resulted in more structurally and compositionally diverse stands leading to multiple successional pathways different from those of even-age pine dominated stands. The recovery and self-organization of unsalvaged natural stands in the Flathead Valley was a complicated process. It has provided insights for future forest management in areas impacted by the current massive MPB epidemic ongoing for the past decade in western North America.