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.
2013
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Tatsiana EspevigAbstract
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Terrestrial lidar (TLS) is an emerging technology for deriving forest attributes, including conventional inventory and canopy characterizations. However, little is known about the influence of scanner specifications on derived forest parameters. We compared two TLS systems at two sites in British Columbia. Common scanning benchmarks and identical algorithms were used to obtain estimates of tree diameter, position, and canopy characteristics. Visualization of range images and point clouds showed clear differences, even though both scanners were relatively high-resolution instruments. These translated into quantifiable differences in impulse penetration, characterization of stems and crowns far from the scan location, and gap fraction. Differences between scanners in estimates of effective plant area index were greater than differences between sites. Both scanners provided a detailed digital model of forest structure, and gross structural characterizations (including crown dimensions and position) were relatively robust; but comparison of canopy density metrics may require consideration of scanner attributes.
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Mallikarjuna Rao Kovi Mats Höglind Hans Martin Hanslin Åshild Ergon Torben Asp Odd Arne RognliAbstract
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Six trap models were compared with respect to their ability to capture European spruce bark beetles and technical details in handling and use. All trap models proved to be efficient and gave high captures of beetles during operation for one summer season (2013). Ranking the trap models in descending order of total capture of beetles gave this list: Lindgren trap, Theysohn, prototype-P, Ecotrap, BEKA, and prototype-K. However, there was much variation in trapping results between localities for all trap models, and the estimated means did in most cases not differ significantly between models. The estimated mean capture of the Lindgren trap was significantly higher than for prototype-K and BEKA, but their confidence intervals were wide and they were close to being insignificantly different. The retail price of the traps vary from about 10 € (Ecotrap) to 50-55 € (Lindgren), while prices are not available for the two prototypes, which are not in regular production. Advantages and disadvantages concerning weight, size, robustness, draining of rain water, ease of handling and mounting are commented on in the discussion, and technical details of the traps are presented in a separate appendix (6).
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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.