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.
2025
Authors
Jian Liu Faruk Djodjic Barbro Ulén Helena Aronsson Marianne Bechmann Lars Bergström Tore Krogstad Katarina KyllmarAbstract
No abstract has been registered
2024
Authors
Kathrine Presthus FylkesnesAbstract
Microalgae are important primary producers of marine ecosystems. Many species require cobalamin (Vitamin B12), which is primarily related to the synthesis of methionine, where cobalamin is cofactor for the enzyme methionine synthase (METH). A gap of knowledge is the required amount of cobalamin needed for growth of cobalamin-dependent organisms and the potential environmental factors that can inactivate cobalamin. Nitrous oxide (N2O) has shown to be a potent inactivator of cobalamin in clinical studies. The greenhouse gas is biologically produced by marine microorganisms, and it is not known whether the concentrations of N2O usually found in marine environments can inhibit growth of cobalamin-dependent microalgae. The aim of this thesis was to investigate the effect of cobalamin depletion and N2O exposure on growth of cobalamin-dependent microalgae. The effect of different concentrations of N2O on growth of cobalamin-dependent E.coli was established in an E.coli model system. Further, the potential for N2O production from microbiota of enriched sediments was investigated in air-tight vials. Growth of cobalamin-dependent I.galbana and T.lutea upon cobalamin depletion was investigated by growing the microalgae in medium without cobalamin. Lastly, N2O effect on algal cultures were tested through injecting growing cultures into air-tight vials containing N2O, followed by measurements of oxygen levels. It was found inactivation of growth of cobalamin-dependent E.coli when presence of saturated concentrations of N2O. This concentration was substantially above the N2O concentrations associated with marine environments and the observed accumulation from enriched sediments. The growth of the cobalamin-dependent microalgae was surprisingly not affected by the absence of cobalamin in medium. Through 16S rRNA analysis, the presence of bacteria was detected in the cultures of these microalgae. Lastly, it was not succeeded to evaluate the effect of N2O on oxygen production from microalgae with the current experimental set-up. In conclusion, saturated concentrations of N2O was shown to inactivate growing cobalamin-dependent E.coli, but the exact inactivation concentration remains undetermined and requires further investigation. As the observed inactivation level was far above the N2O concentrations associated with marine environments, the results suggests that the N2O concentrations usually found in such environments are insufficient to impact the growth of resident cobalamin-dependent organisms. Further, if the non-observed effect of cobalamin depletion on growth of cobalamin-dependent microalgae is caused by the presence of cobalamin-producers or other factors could be investigated further. Lastly, as it was not possible to evaluate the effect of N2O on microalgal growth, this should be investigated further.
Authors
Tatiana F. Rittl Anne de Boer Reidun Pommeresche Anne-Kristin LøesAbstract
Data paper
Authors
Mostafa Hoseini Helle Ross Gobakken Stephan Hoffmann Csongor Horvath Johannes Rahlf Jan Bjerketvedt Stefano Puliti Rasmus AstrupAbstract
No abstract has been registered
Abstract
Large clear-cut areas as a consequence of drought and bark beetle infestations necessitate extensive replanting efforts in German forests, leading to an increased interest in efficient planting systems. In addition to manual planting, mechanized and semi-mechanized systems utilizing surplus forest machine capacities available after completion of salvage logging operations are likely required for timely reforestation of the clear-cut areas. A semi-mechanized system utilizing a standard forwarder with a grapple-actuated soil borer for both, the transport of planting material and the preparation of planting pits, combined with two workers carrying out manual planting, was investigated in a time-and-motion study. The frequency method was used after video recording of a planting operation that covered an area of approximately 1.2 hectares. A total of 815 alder saplings (Alnus glutinosa L.) with heights of 1.2–1.5 m were planted. Observed productivity was 93 saplings per system work hour (SWH). With additional placement of stakes for stabilizing the plants, the productivity decreased to 42 saplings per SWH. While directly comparable results were not found in the literature, available productivity figures of purely manual planting systems do not suggest an increased productivity of this semi-mechanized system. Considering ergonomics, however, forwarder utilization provides reduced workload not only in plant hole preparation but also with material transport and clearing of planting spots. Both the ergonomic aspects of the system and, in particular, the suitability of the soil borer for different soil textures should be further investigated.
Abstract
Background: Small-scale forests (woodlots) increasingly account for a greater proportion of the total annual harvest in New Zealand. There is limited information on the extent of infrastructure required to harvest a woodlot; road density (trafficable with log trucks), landing size, or the average harvest area that each landing typically services. Methods: This study quantified woodlot infrastructure averages and evaluated influencing factors. Using publicly available aerial imagery, roads and landings were mapped for a sample of 96 woodlots distributed across the country. Factors such as total harvest area, average terrain slope, length/width ratio, boundary complexity and extraction method were recorded and investigated for correlations. Results: The average road density was 25 m/ha, landing size was 3000 m2 and each landing was serviced on average 12.8 ha. Notably, 15 of the 96 woodlots had no internal infrastructure, with the harvest completed using roads and landings located outside of the woodlot boundary. Factors influencing road density were woodlot length/width ratio, average terrain slope and boundary complexity. Landing size was influenced by average terrain slope, woodlot length/width ratio, and woodlot area. Conclusion: The results provide a contemporary benchmark of the current infrastructure requirements when harvesting a small-scale forests in New Zealand. These may be used at a high level to infer the total annual infrastructure investment in New Zealand's woodlot estate and also project infrastructure requirements over the foreseeable future. Keywords: forest infrastucture, small-scale forestry
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Helle Ross Gobakken Mostafa Hoseini Stephan Hoffmann Jan Bjerketvedt Johannes Rahlf Rasmus AstrupAbstract
No abstract has been registered
Abstract
Point clouds from laser scanning are a standard data source in forest research, but the lack of clear and robust workflows has limited the translation of experimental knowledge into operational tools. We present a novel machine learning-based workflow that uses individual-tree point clouds from drone laser scanning to predict wood quality parameters. Unlike object reconstruction methods, our approach is based on simple metrics computed on vertical slices that summarize information of point distances, angles, and geometric attributes of the empty space between and around the points. Our models use these slice metrics as predictors and achieve high accuracy for predicting diameter of the largest branch per whorl (DLBw) and stem diameter at different heights (DSi) from survey-grade drone laser scans. We show that our models are also robust and accurate when tested on suboptimal versions of the data generated by reductions in the number of points or emulations of suboptimal segmentation scenarios. Our approach provides a simple, clear, and scalable solution that can be adapted to different situations and has the potential to revolutionize forest management and monitoring