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.
2018
Authors
Svein SolbergAbstract
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In the Nordic-Baltic region, there has been a growing concern about an increasing occurrence of multiple tops in young stands of Norway spruce. There is however a lack of documentation on the amount of such damages, and the causal agents involved. In two separate studies in SE Norway, we assessed the frequency of multiple tops in young sapling-sized stands, and studied the relationship between the occurrence of multiple tops and lammas growth the previous growing season on the sample trees. Study 1 included 44 planted and 10 naturally regenerated stands, while Study 2 included 68 planted stands with information on seed source. Among sample trees with multiple tops, 57% (Study 1) and 32% (Study 2) had signs of lammas growth the previous autumn, either in the form of an extended leading shoot or swollen bud. Site index as well as sample tree height were positively correlated to the occurrence of both lammas growth and multiple tops in both studies. In Study 1 we show that the probability of lammas growth was significantly higher in planted than in naturally regenerated stands. In Study 2 we show that it was higher in stands planted with seedlings grown from stand-origin seeds compared with improved seed material. Furthermore, the results of both studies show that lammas growth occurs most frequently among the dominant trees in the stand.
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Authors
Svein Solberg Johannes May Wiley Steven Bogren Johannes Breidenbach Torfinn Torp Belachew Gizachew ZelekeAbstract
Monitoring changes in forest height, biomass and carbon stock is important for understanding the drivers of forest change, clarifying the geography and magnitude of the fluxes of the global carbon budget and for providing input data to REDD+. The objective of this study was to investigate the feasibility of covering these monitoring needs using InSAR DEM changes over time and associated estimates of forest biomass change and corresponding net CO2 emissions. A wall-to-wall map of net forest change for Uganda with its tropical forests was derived from two Digital Elevation Model (DEM) datasets, namely the SRTM acquired in 2000 and TanDEM-X acquired around 2012 based on Interferometric SAR (InSAR) and based on the height of the phase center. Errors in the form of bias, as well as parallel lines and belts having a certain height shift in the SRTM DEM were removed, and the penetration difference between X- and C-band SAR into the forest canopy was corrected. On average, we estimated X-band InSAR height to decrease by 7 cm during the period 2000–2012, corresponding to an estimated annual CO2 emission of 5 Mt for the entirety of Uganda. The uncertainty of this estimate given as a 95% confidence interval was 2.9–7.1 Mt. The presented method has a number of issues that require further research, including the particular SRTM biases and artifact errors; the penetration difference between the X- and C-band; the final height adjustment; and the validity of a linear conversion from InSAR height change to AGB change. However, the results corresponded well to other datasets on forest change and AGB stocks, concerning both their geographical variation and their aggregated values.
Authors
Jonathan Rizzi Clara Antón Fernández Paulo Jorge de Almeida Borges Ryan Bright Rasmus AstrupAbstract
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Authors
Tonje Økland Jørn-Frode Nordbakken Holger Lange Ingvald Røsberg Kjersti Holt Hanssen Nicholas ClarkeAbstract
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Climate change could increase fire risk across most of the managed boreal forest. Decreasing this risk by increasing the proportion of broad-leaved tree species is an overlooked mitigation–adaption strategy with multiple benefits.