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Debella-Gilo M.,Norwegian Institute of Bioeconomy Research NIBIO As
International Journal of Remote Sensing | Year: 2016

A method of extracting bare-earth points from photogrammetric point clouds by partially using an existing lower resolution digital terrain model (DTM) is presented. The bare-earth points are extracted based on a threshold defined by local slope. The local slope is estimated from the lower resolution DTM. A gridded DTM is then interpolated from the extracted bare-earth points. Five different interpolation algorithms are implemented and evaluated to identify the most suitable interpolation method for such non-uniformly scattered data. The algorithm is tested on four test sites with varying topographic and ground cover characteristics. The results are evaluated against a reference DTM created using aerial laser scanning. The deviations of the extracted bare-earth points, and the interpolated DTM, from the reference DTM increases with increasing forest canopy density and terrain roughness. The DTM created by the method is significantly closer to the reference DTM than the lower resolution national DTM. The ANUDEM (Australian National University Digital Elevation Modelling) interpolation method is found to be the best performing interpolation method in terms of reducing the deviations and in terms of modelling the terrain realistically with minimum artefacts, although the differences among the interpolation methods are not considerably large. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Dalsgaard L.,Norwegian Institute of Bioeconomy Research NIBIO As | Astrup R.,Norwegian Institute of Bioeconomy Research NIBIO As | Anton-Fernandez C.,Norwegian Institute of Bioeconomy Research NIBIO As | Borgen S.K.,Norwegian Institute of Bioeconomy Research NIBIO As | And 4 more authors.
PLoS ONE | Year: 2016

Boreal forests contain 30% of the global forest carbon with the majority residing in soils. While challenging to quantify, soil carbon changes comprise a significant, and potentially increasing, part of the terrestrial carbon cycle. Thus, their estimation is important when designing forest-based climate change mitigation strategies and soil carbon change estimates are required for the reporting of greenhouse gas emissions. Organic matter decomposition varies with climate in complex nonlinear ways, rendering data aggregation nontrivial. Here, we explored the effects of temporal and spatial aggregation of climatic and litter input data on regional estimates of soil organic carbon stocks and changes for upland forests. We used the soil carbon and decomposition model Yasso07 with input from the Norwegian National Forest Inventory (11275 plots, 1960-2012). Estimates were produced at three spatial and three temporal scales. Results showed that a national level average soil carbon stock estimate varied by 10% depending on the applied spatial and temporal scale of aggregation. Higher stocks were found when applying plot-level input compared to country-level input and when long-term climate was used as compared to annual or 5-year mean values. A national level estimate for soil carbon change was similar across spatial scales, but was considerably (60-70%) lower when applying annual or 5-year mean climate compared to long-term mean climate reflecting the recent climatic changes in Norway. This was particularly evident for the forest-dominated districts in the southeastern and central parts of Norway and in the far north. We concluded that the sensitivity of model estimates to spatial aggregation will depend on the region of interest. Further, that using long-term climate averages during periods with strong climatic trends results in large differences in soil carbon estimates. The largest differences in this study were observed in central and northern regions with strongly increasing temperatures. Copyright © 2016 Dalsgaard et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Nussbaumer A.,Swiss Federal Institute of forest | Waldner P.,Swiss Federal Institute of forest | Etzold S.,Swiss Federal Institute of forest | Gessler A.,Swiss Federal Institute of forest | And 13 more authors.
Forest Ecology and Management | Year: 2016

Occurrence of mast years, i.e. the synchronous production of vast amounts of fruits or seeds, has an important impact on forest ecosystems, their functioning and their services. We investigated the mast patterns of the forest tree species common beech, common and sessile oak, Norway spruce and Scots pine in Central and Northern Europe over the last two to three decades. We analysed data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and additional Danish, German, Flemish and Swiss datasets.Within-plot synchrony of fructification intensity in individual trees was high in beech and spruce and lower in oak species and pine. Mast frequency increased in most regions for beech, whereas the other species showed mixed or no trends. Beech, oak species and spruce showed strong mast year (MY) synchrony, but pine did not. MY synchrony between species was only significant in Bavaria, in Switzerland and between beech, oak species and spruce in Denmark. The deciduous species showed bimodal normal masting, while the conifers had switching normal masting. Oak species and the conifers supported the large seed and the accessory costs hypotheses, and beech and spruce supported the economy of scale, predator satiation and resource allocation hypotheses. © 2015 Elsevier B.V..

Ma X.,Heilongjiang Academy of Agricultural science | Ma X.,Norwegian Institute of Bioeconomy Research NIBIO As | Zhou B.,Heilongjiang Academy of Agricultural science | Budai A.,Norwegian Institute of Bioeconomy Research NIBIO As | And 5 more authors.
Communications in Soil Science and Plant Analysis | Year: 2016

Biochar is a carbon-rich solid product obtained by pyrolysis of biomass. Here, we investigated multiple biochars produced under slow pyrolysis (235–800 °C), flash carbonization, and hydrothermal carbonization (HTC), using Scanning Electron Microscope—Energy Dispersive X-ray Spectroscopy (SEM-EDX) in order to determine whether SEM-EDX can be used as a proxy to characterize biochars effectively. Morphological analysis showed that feedstock has an integrated structure compared to biochar; more pores were generated, and the size became smaller when the temperature increased. Maximum carbon content (max. C) and average carbon content (avg. C) obtained from SEM-EDX exhibited a positive relationship with pyrolysis temperature, with max. C correlating most closely with dry combustion total carbon content. The SEM-EDX O/C ratios displayed a consistent response with the highest treatment temperature (HTT). The study suggests that SEM-EDX produces highly consistent C, oxygen (O), and C/O ratios that deserve further investigation as an operational tool for characterization of biochar products. © 2016 Taylor & Francis

Gundersen V.,Norwegian Institute for Nature Research | Clarke N.,Norwegian Institute of Bioeconomy Research NIBIO As | Dramstad W.,Norwegian Institute of Bioeconomy Research NIBIO As | Fjellstad W.,Norwegian Institute of Bioeconomy Research NIBIO As
Scandinavian Journal of Forest Research | Year: 2016

Increased forest biomass production for bioenergy will have various consequences for landscape scenery, depending on both the landscape features present and the character and intensity of the silvicultural and harvesting methods used. We review forest preference research carried out in Finland, Sweden and Norway, and discuss these findings in relation to bioenergy production in boreal forest ecosystems. Some production methods and related operations incur negative reactions among the public, e.g. stump harvesting, dense plantation, soil preparation, road construction, the use of non-native species, and partly also harvest of current non-productive forests. Positive visual effects of bioenergy production tend to be linked to harvesting methods such as tending, thinning, selective logging and residue harvesting that enhance both stand and landscape openness, and visual and physical accessibility. Relatively large differences in findings between studies underline the importance of local contextual knowledge about landscape values and how people use the particular landscape where different forms of bioenergy production will occur. This scientific knowledge may be used to formulate guiding principles for visual management of boreal forest bioenergy landscapes. © 2015 Taylor & Francis.

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