| 1. |
- Dagsson-Waldhauserova, P., et al.
(författare)
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Physical properties of suspended dust during moist and low wind conditions in Iceland
- 2014
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Ingår i: Icelandic Agricultural Sciences. - 1670-567X. ; 27, s. 25-39
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Tidskriftsartikel (refereegranskat)abstract
- We measured a dust event which occurred during wet and low wind/windless conditions as the result of surface heating in August 2013. Maximum particle number concentration (PM similar to 0.3-10 mu m) reached 149,954 particles cm(-3) min(-1) while mass concentration (PM<10 m) was 1757 g m-3 min-1. The suspended dust was very fine with the highest number of particles in the size range 0.3-0.337 mu m, followed by particles 1.5-5 mu m in diameter. Close-to-ultrafine particle size distributions showed a significant increase in number with the severity of the measured dust event (during dust peaks). Number concentrations were well correlated with mass concentrations. The mineralogy and geochemical compositions showed that glaciogenic dust contains sharp-tipped shards with bubbles and 80 % of the particulate matter is volcanic glass rich in heavy metals. Wet dust particles were mobilized within < 4 hours. This is the first scientific study of particle size distributions in an Icelandic dust event including findings on initiation of dust suspension.
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| 2. |
- Granquist, Sandra M., et al.
(författare)
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Diet of harbour seals in a salmon estuary in North-West Iceland
- 2016
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Ingår i: Icelandic Agricultural Sciences. - 1670-567X. ; 29, s. 7-19
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Tidskriftsartikel (refereegranskat)abstract
- The effect of harbour seal predation on salmonids has been frequently debated, although interactions between these species have never been thoroughly investigated in Icelandic waters prior to this study. We investigated the diet of harbour seals in a salmon estuary in NW Iceland between 2009 and 2011, using hard part analysis from collected faeces. No evidence of seal predation on salmonids was found in the study. The reconstructed weight and estimated energy content of prey species showed that flatfish was the most important species group, followed by Ammodytidae. The species group found in the highest proportion of samples during the three years combined was also Ammodytidae (45% of the samples). Ammodytidae, flatfishes and capelin dominated by numerical occurrences. However, inter- and intra-annual variation was found regarding the diet.
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| 3. |
- Jägerbrand, Annika K.
(författare)
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Patterns of species richness and vegetative performance in heath ecosystems at Thingvellir, Southwest Iceland
- 2004
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Ingår i: Icelandic Agricultural Sciences. - : Agricultural University of Iceland. - 1670-567X. ; 16-17, s. 29-38
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Tidskriftsartikel (refereegranskat)abstract
- The Racomitrium lanuginosum (Hedw.) Brid. moss heath is a unique environment and is of great importance for co-occurring established vascular plants. A thick moss carpet can prevent or restrict the growth of vascular plants as they are exposed to more unfavourable growth conditions, but the effect on species richness and abundance is less known. To investigate the negative effects of a well-developed moss carpet on established vascular plants, patterns of species richness, shoot density, and number of leaves (Carex bigelowii Schwein. and Thalictrum alpinum L.) were studied in two different vegetation types, Racomitrium lanuginosum moss heath, and dwarf shrub heath in Þingvellir National Park, Southwest Iceland.Species richness was higher in dwarf shrub heath and increased proportionally with the size of the shrub patches. Total species richness and plant functional dominance did not differ between vegetation types. There were no differences found in shoot density, percentage of flowering and juveniles, number of leaves in Carex bigelowii, or shoot density, flowering percentage or number of leaves in Thalictrum alpinum between the vegetation types. However, leaf length of Carex bigelowii was higher in the dwarf shrubs heath, indicating more favourable growth conditions, shade or shelter effects. It is possible that translocation is taking place between the shoots of the clonal vascular plants in this study so that the plants themselves are counteracting unfavourable effects in the different vegetation types. The effect of global climatic change on moss heaths in Iceland is briefly discussed.
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| 4. |
- Nyström, Kenneth
(författare)
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Stem volume and above ground biomass models for Sitka spruce (Picea sitchensis (Bong.) Carr.) in Iceland
- 2023
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Ingår i: Icelandic Agricultural Sciences. - 1670-567X .- 2298-786X. ; 36, s. 69-80
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Tidskriftsartikel (refereegranskat)abstract
- The prediction of tree biomass and stem volume is necessary for monitoring and assessing of national forest biomass, carbon stock and sustainable forest management. Such predictions of biomass or carbon stocks are generated by using either allometric models or applying biomass expansion factors (BEFs), where the former is a better method. Volume models are generated by using allometric models. The data for development of the new volume and biomass models for Iceland presented in this paper were collected between years 2000-2021, from 48 locations in even aged stands that were planted between 1942-1983. Because of the young age of forest plantations in Iceland, existing biomass and volume models need to be updated regularly as trees get older and larger. The new models use the same independent variables as the previous ones for Iceland but use a wider approach and have a different form than the older ones. Using the previous Icelandic models outside their data range results in underestimation for both aboveground biomass and stem volume.
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| 5. |
- Sigurdsson, Bjarni D., et al.
(författare)
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Geothermal ecosystems as natural climate change experiments : The ForHot research site in Iceland as a case study
- 2016
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Ingår i: Icelandic Agricultural Sciences. - 1670-567X. ; 29:1, s. 53-71
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Tidskriftsartikel (refereegranskat)abstract
- This article describes how natural geothermal soil temperature gradients in Iceland have been used to study terrestrial ecosystem responses to soil warming. The experimental approach was evaluated at three study sites in southern Iceland one grassland site that has been warm for at least 50 years (GO), and another comparable grassland site (GN) and a Sitka spruce plantation (FN) site that have both been warmed since an earthquake took place in 2008. Within each site type, five ca. 50 m long transects, with six permanent study plots each, were established across the soil warming gradients, spanning from unwarmed control conditions to gradually warmer soils. It was attempted to select the plots so the annual warming levels would be ca. +1, +3, +5, +10 and +20 °C within each transect. Results of continuous measurements of soil temperature (Ts) from 2013-2015 revealed that the soil warming was relatively constant and followed the seasonal Ts cycle of the unwarmed control plots. Volumetric water content in the top 5 cm of soil was repeatedly surveyed during 2013-2016. The grassland soils were wetter than the FN soils, but they had sometimes some significant warming-induced drying in the surface layer of the warmest plots, in contrast to FN. Soil chemistry did not show any indications that geothermal water had reached the root zone, but soil pH did increase somewhat with warming, which was probably linked to vegetation changes. As expected, the potential decomposition rate of organic matter increased significantly with warming. It was concluded that the natural geothermal gradients at the ForHot sites in Iceland offered realistic conditions for studying terrestrial ecosystem responses to warming with minimal artefacts.
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