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.
2003
Authors
Øystein JohnsenAbstract
No abstract has been registered
Authors
Peder Gjerdrum Olav Albert HøibøAbstract
Pine heart- and sapwood can in several respects be considered two different timber products, demonstrating separate wood properties. The efficiency of automated heart- and sapwood separation by analysing temperature images of pine crosscuts has been investigated. A digital, infrared (IR) ThermoVisionfocal plane array camera with 320*240 pixels was employed. IR exposures of the front-end crosscut of 180 pine sawlogs were taken during longitudinal transport on a conveyor, arbitrary crosscut being in front. In each image, one arbitrary diameter was chosen for estimating the heart-wood. The temperature gradient between heart- and sapwood was in the range up to 4oC. An algorithm was established to calculate front-end heartwood diameter as a fraction of log diameter. The correlation between estimated and observed heartwood fraction was r = 0.85. Finally, top end heartwood diameter in mm could be calculated by multiplying top-end diameter, as measured in an ordinary log scanner, with heartwood fraction in front (arbitrary) end. For fresh logs RMSE amounted to 11 mm (front: top end) and 15 mm (front: arbitrary end), respectively. It was concluded that the method might be applicable for an industrial log sorting system and might have a potential to indicate even other wood characteristics. The temperature gradient between heart- and sapwood showed to be a reliable criterion for the accuracy of the model. The temperature gradient might even be used to indicate log freshness.
Authors
Peder GjerdrumAbstract
Knowledge about the transformation of sapwood into heartwood contributes to the understanding of the nature of pine trees and should be considered prior to the conversion of sawlogs to produce timber of prescribed properties and optimal revenue. In this study, heartwood formation was ascribed to the joint effect of ageing and growth rate. Observations of heart- and sapwood in 1656 trees and sawlogs of Scots pine (Pinus sylvestris L.), sampled throughout Scandinavia, were analysed using mixed models. The most important finding was expressed in the pine heartwood age rule: heartwood age equals the square root of cambial age less three, to the second power. This global formula was valid irrespective of environmental factors and location within the tree, and described 93 per cent of the variance in the sample. Transition rate increases from 0.6 rings a−1 at 50 years to 0.8 rings a−1 at 200 years. The spatial amount of heartwood might be influenced by the silviculture through the annual ring width pattern. For samples missing sapwood, e.g. archaeological wood, the results might be combined with dendrochronology in specimen dating. When the diameter and the heartwood diameter of sawlogs were known, the mean annual ring width could be estimated with a standard deviation of 0.5 mm a−1. The simplicity, consistency and high correlation of the pine heartwood age rule confirms the importance of age as the main factor in heartwood formation.
Authors
Ulf SikströmAbstract
No abstract has been registered
Authors
Kari M. Laine Oddvar Skre Frans-Emil WielgolaskiAbstract
HIBECO-prosjektet har fokusert på naturleg og menneskeleg påverknad på bjørke-økosystemet, og på å utforma ulike skjøtsel-scenarier og skogutvikling for å sikra vidare bærekraftig bruk av bjørkeskogen. Dette er oppnådd ved å ta i bruk ulike faglege disiplinar som kombinerer produktivitet, beiting og sosio-økonomiske forhold. Det var ein markert skilnad mellom proveniensar i frostherdighet og vekst. Insektskader på grunn av Epirrita autumnata var sterkt avhengig av vintertemperatur og av vekstformen hos bjørka. Samanliknande studier viste kraftig reduksjon i lavdekket på Finnmarksvidda sidan 1960-talet, og auke i arealet av Cornus suecica og mose, på grunn av overbeiting av reinsdyr og endra klima. Tradisjonell bruk av bjørk er blitt undersøkt ved ei omfattande spørjeundersøking. Det er blitt utvikla ein dynamisk modell for å få kunnskap om dei langsiktige konsekvensane av endra klima og arealbruk innan seks forsøksområde på 100 x 100 km i Nord-Skandinavia og Island.
Authors
Holger LangeAbstract
No abstract has been registered
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No abstract has been registered
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No abstract has been registered
Abstract
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Authors
Yi He Jixi Gao Haiying Liu Zhengtao Liu Feng Liu Xiaoshan Zhang Jingheng Guo Yanhui Wang He Shang Pengtao Yu Jianhua Zhu Jingjun Han Bin Yao Xiyon Hu Xiaoquan Zhang Min Shao Limin Zeng Lei Jin Lei Duan Quanru Liu Dawei Zhao Dongbao Zhang Shengliang Chen Renjun Xiang Yi Chang Jinhong Zhang Jiahai Luo Zhanyi Zhang Jinsong Xiao Xiaoyu Peng Rolf David Vogt Hans Martin Seip Wenche Aas Kjetil Tørseth Jan Mulder Trine Sogn Odd Eilertsen Tonje Økland Harald Bratli Valter Angell Svein Solberg Tor Myking Espen Lydersen Thorjørn Larssen Dagang TangAbstract
Sulphur deposition is high at all IMPACTS sites and exceed maximum levels observed in Europe and North-America. Dry deposition equals or exceeds wet deposition. The IMPACTS data, in particular those from the remote Lei Gong Shan site clearly document long-range transport of air pollutants. Due to the actual and future energy combustion and emission strategy in China, the long-range transport of air pollutants may significantly increase with subsequent increased environmental damage in rural and remote areas in China. In addition to sulphur deposition, depositions of reactive nitrogen (nitric acid and ammonia) and calcium are also important and clearly demonstrate that pH alone is not a good indicator for acid deposition. High concentrations of ground level ozone, above critical levels for vegetation and forest, are observed at the Liu Xi He site in Guangdong province. Soil acidification gives rise to high concentrations of toxic aluminium in soil water at several sites. At the Tie Shan Ping site in Chongqing aluminium occurs at a level where long-term harmful effects on trees might be expected. Defoliation and mortality have been severe, however, fairly stable. Insect attacks are apparently a major cause, but enhanced insect attacks might be an indirect effect of health weakening due to acidification. Defoliation has been considerable also in Liu Chong Guan in Guiyang, while the three other catchments had minor defoliation only. High foliar nitrogen concentrations are seen in Lei Gong Shan in Guizhou and Cai Jia Tang in Hunan, accompanied by low P/N-ratios. Statistical tests of vegetation change, so far only implemented in Liu Chong Guan, revealed minor changes in number and abundances of vascular plants, but a significant decline in number of bryophytes. This decline is probably related to climatic year-to-year variations. Data from other catchments and longer time periods are needed to identify vegetation changes related to soil acidification or direct effects of air pollutants. Modelling results from Tie Shan Ping suggest that the currently planned 20% reduction in sulphur emissions is far from sufficient to avoid further acidification. As more data are generated, dose-response relationships, critical load estimates and model predictions will obviously be improved.