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Siglufjordur, Iceland

The Agricultural University of Iceland is an educational and research institution focusing on agricultural and environmental science, founded in 2005. The university's facilities are mainly located at Hvanneyri, near Borgarnes, Iceland but it also operates research stations in Reykjavík, Árnessýsla and Eyjafjarðarsýsla. Wikipedia.

Thorarinsdottir E.F.,Soil Conservation Service | Arnalds O.,Agricultural University of Iceland
Aeolian Research | Year: 2012

Iceland has extensive areas with intense aeolian processes, in spite of humid climate. We measured wind erosion in a 110km 2 heterogeneous sandy area near the Mt. Hekla volcano in South Iceland. The area is sparsely vegetated and covered by volcanic materials. Measurements were made during two summer seasons in 2008-2009 with dust traps at 25 locations employing a 'single dust trap method' after characterizing sediment height profiles. Sets of electronic equipment that measured wind erosion and several weather parameters were placed at two locations. The results show a large variation in sediment transport with maximum transport in storms ranging from 0 to 1788kgm -1 at each site and maximum average transport during storm reaching 244kgm -1h -1. The aeolian transport each summer ranged from 1 to 2981kgm -1. Amount of loose sandy sediments on the surface, sediment texture and proximity to water channels are important factors explaining site differences. Wind erosion was most intense in the north-eastern part of the area, with >80% loose sand on the surface but less intense closest to the volcano where coarse pumice characterizes the surface. The research shows a pathway of sediment transport on a landscape scale with north-easterly winds, into the Thjorsa river, enhanced by landscape characteristics and seasonally active water channel. Pumice grains >8mm in diameter were transported by saltation. Grains >1mm were commonly >20% of materials collected at 30cm height, which is explained by low density of the volcanic materials and high wind velocities. © 2012 Elsevier B.V.. Source

Arnalds O.,Agricultural University of Iceland
Advances in Agronomy | Year: 2013

Volcanic eruptions affect a large proportion of Earth's ecosystems, ranging from subtle dust inputs to thick deposits near the volcanoes. In this chapter, multiple influences of tephra deposition on land are investigated, using examples of recent volcanic eruptions. "Tephra" is the collective term for airborne volcanic materials, while ash is restricted to materials <2mm in grain size. Impacts of tephra is depended on the nature of the tephra, including crystallinity, chemical composition, and grain size. The interaction between vegetation height and the deposition depth has a major influence on impacts, while surface roughness and other factors are also important. Low growing Arctic, alpine, and desert ecosystems are much more sensitive than higher vegetation and forests. Recovery time ranges from few to >1000 years. Alien species can severely interfere with ecosystem recovery. Erosion processes contribute to volcanic impacts by redistributing tephra, thus reducing tephra thicknesses in some places, but can also cause erosion rates exceeding 100,000tkm-2 year-1. Wind erosion of tephra affects ecosystems, agriculture, and health but can provide beneficial dust inputs afar. Thick tephra deposits have pronounced impacts on agriculture, and F toxicity is common in volcanic areas. Soils that form in parent materials dominated by volcanic ash are mostly Andisols with the colloidal fraction dominated by short range order minerals and metal-humus complexes. Andisols are often fertile soils with a high capacity to accumulate carbon. There is a need for multidisciplinary long-term research on impacts and responses to volcanic eruptions. © 2013 Elsevier Inc. Source

Vesterdal L.,Copenhagen University | Clarke N.,Norwegian Forest And Landscape Institute | Sigurdsson B.D.,Agricultural University of Iceland | Gundersen P.,Copenhagen University
Forest Ecology and Management | Year: 2013

Information on tree species effects on soil organic carbon (SOC) stocks is scattered and there have been few attempts to synthesize results for forest floor and mineral soil C pools. We reviewed and synthesized current knowledge of tree species effects on SOC stocks in temperate and boreal forests based on common garden, retrospective paired stand and retrospective single-tree studies. There was evidence of consistent tree species effects on SOC stocks. Effects were clearest for forest floor C stocks (23 of 24 studies) with consistent differences for tree genera common to European and North American temperate and boreal forests. Support for generalization of tree species effects on mineral soil C stocks was more limited, but significant effects were found in 13 of 22 studies that measured mineral soil C.Proportional differences in forest floor and mineral soil C stocks among tree species suggested that C stocks can be increased by 200-500% in forest floors and by 40-50% in top mineral soil by tree species change. However, these proportional differences within forest floors and mineral soils are not always additive: the C distribution between forest floor and mineral soil rather than total C stock tends to differ among tree species within temperate forests. This suggests that some species may be better engineers for sequestration of C in stable form in the mineral soil, but it is unclear whether the key mechanism is root litter input or macrofauna activity. Tree species effects on SOC in targeted experiments were most consistent with results from large-scale inventories for forest floor C stocks whereas mineral soil C stocks appeared to be stronger influenced by soil type or climate than by tree species at regional or national scales. Although little studied, there are indications that higher tree species diversity could lead to higher SOC stocks but the role of tree species diversity per se vs. species identity effects needs to be disentangled in rigorous experimental designs.For targeted use of tree species to sequester soil C we must identify the processes related to C input and output, particularly belowground, that control SOC stock differences. We should also study forms and stability of C along with bulk C stocks to assess whether certain broadleaves store C in more stable form. Joint cooperation is needed to support syntheses and process-oriented work on tree species and SOC, e.g. through an international network of common garden experiments. © 2013 Elsevier B.V. Source

Sigurdsson B.D.,Agricultural University of Iceland | Magnusson B.,Icelandic Institute of Natural History
Biogeosciences | Year: 2010

When Surtsey rose from the North Atlantic Ocean south of Iceland in 1963, it became a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structures and functions. In July, 2004, ecosystem respiration rate (Re), soil properties and surface cover of vascular plants were measured in 21 permanent research plots distributed among the juvenile communities of the island. The plots were divided into two main groups, inside and outside a seagull (Larus spp.) colony established on the island. Vegetation cover of the plots was strongly related to the density of gull nests. Occurrence of nests and increased vegetation cover also coincided with significant increases in Re, soil carbon, nitrogen and C:N ratio, and with significant reductions in soil pH and soil temperatures. Temperature sensitivity (Q10 value) of Re was determined as 5.3. When compared at constant temperature the Re was found to be 59 times higher within the seagull colony, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The amount of soil nitrogen, mainly brought onto the island by the seagulls, was the critical factor that most influenced ecosystem fluxes and vegetation development on Surtsey. The present study shows how ecosystem activity can be enhanced by colonization of animals that transfer resources from a nearby ecosystem. © 2010 Author(s). Source

Oskarsson U.,Agricultural University of Iceland
Scandinavian Journal of Forest Research | Year: 2010

The importance of nursery practices for seedling mycorrhization and field performance was investigated under nursery and field conditions on nutrient-deficient land in a reclamation area in Iceland. Containerized downy birch (Betula pubescens Ehrh.) seedlings were grown with or without ectomycorrhizal inoculum in two potting substrates (commercial Sphagnum peat moss and local sedge peat). Seedlings were, furthermore, subjected to two fertilizer regimes: constant nutrient strength and initially dilute but escalating nutrient strength. In the nursery, seedlings in Sphagnum peat moss fed with constant nutrient strength grew better than plants in other treatments. Sedge peat, escalating nutrient strength and inoculum was the only treatment combination that provided conditions for prolific mycorrhization in the nursery. In the field, seedlings subjected to mycorrhizal inoculation and/or escalating nutrient strength survived better and had less shoot dieback than seedlings of contrasting treatments. Furthermore, seedlings raised in sedge peat substrate grew better in the field than seedlings raised in Sphagnum peat moss. Seedling mycorrhization at planting correlated positively with seedling field survival and growth and negatively with shoot dieback. The results illustrate that biological and chemical substrate conditions in the nursery can be decisive for the mycorrhizal development and field performance of tree seedlings. © 2010 Taylor & Francis. Source

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