Browsing by Subject "117 Geography, Environmental sciences"

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  • Kozlovskaya, E.; Elo, S.; Hjelt, S.-E.; Yliniemi, J.; Pirttijärvi, M.; SVEKALAPKO Seismic Tomography Work (2004)
  • Hagner, Marleena; Penttinen, Olli-Pekka; Pasanen, Tiina; Tiilikkala, Kari; Setala, Heikki (2010)
  • Plyusnin, Ilya; Evans, Alistair R; Karme, Aleksis; Gionis, Aristides; Jernvall, Jukka (2008)
  • Partanen, Pasi; Hultman, Jenni; Paulin, Lars; Auvinen, Petri; Romantschuk, Martin (2010)
  • Mikola, Juha; Setälä, Heikki; Virkajärvi, P; Saarijärvi, K; Ilmarinen, K; Voigt, W; Vestberg, M (2009)
    Large herbivores can influence plant and soil properties in grassland ecosystems, but especially for belowground biota and processes, the mechanisms that explain these effects are not fully understood. Here, we examine the capability of three grazing mechanisms-plant defoliation, dung and urine return, and physical presence of animals (causing trampling and excreta return in patches)-to explain grazing effects in Phleum pratense-Festuca pratensis dairy cow pasture in Finland. Comparison of control plots and plots grazed by cows showed that grazing maintained original plant-community structure, decreased shoot mass and root N and P concentrations, increased shoot N and P concentrations, and had an inconsistent effect on root mass. Among soil fauna, grazing increased the abundance of fungivorous nematodes and Aporrectodea earthworms and decreased the abundance of detritivorous enchytraeids and Lumbricus earthworms. Grazing also increased soil density and pH but did not affect average soil inorganic-N concentration. To reveal the mechanisms behind these effects, we analyzed results from mowed plots and plots that were both mowed and treated with a dung and urine mixture. This comparison revealed that grazing effects on plant attributes were almost entirely explained by defoliation, with only one partly explained by excreta return. Among belowground attributes, however, the mechanisms were more mixed, with effects explained by defoliation, patchy excreta return, and cow trampling. Average soil inorganic-N concentration was not affected by grazing because it was simultaneously decreased by defoliation and increased by cow presence. Presence of cows created great spatial heterogeneity in soil N availability and abundance of fungivorous nematodes. A greenhouse trial revealed a grazing-induced soil feedback on plant growth, which was explained by patchiness in N availability rather than changes in soil biota. Our results show that grazing effects on plant attributes can be satisfactorily predicted using the effects of defoliation, whereas those on soil fauna and soil N availability need understanding of other mechanisms as well. The results indicate that defoliation-induced changes in plant ecophysiology and the great spatial variation in N availability created by grazers are the two key mechanisms through which large herbivores can control grassland ecosystems.
  • Lehtiniemi, Maiju; Pääkkönen, Jari-Pekka; Flinkman, Juha; Katajisto, Tarja; Gorokhova, Elena; Karjalainen, Miina; Viitasalo, Satu; Björk, Heidi (2007)
  • Setälä, Heikki (EASAC Secretariat, The Royal Society, 2009)
    EASAC policy report
  • Hagner, Marleena; Pasanen, Tiina; Lindqvist, Bengt; Lindqvist, Isa; Tiilikkala, Kari; Penttinen, Olli-Pekka; Setala, Heikki (2010)
  • Hietanen, Susanna; Lukkari, Kaarina (2007)
    Whether sediments act as sinks or sources of nutrients depends partly on the oxygen conditions at the seafloor. Laboratory experiments on coastal Gulf of Finland (Baltic Sea) sediment tested the sensitivity of denitrification to a 2 wk anoxia exposure and subsequent reoxidation of the bottom waters. At the same time we followed the rapidly (1 d) and more slowly (9 d) emerging changes in different forms of sediment P after oxic conditions were restored. The total denitrification rate (Dtot) did not change during anoxic incubation, but shifted from coupled nitrification-denitrification (Dn) towards water column nitrate dependence (Dw). As the Dn rate did not decrease at the same rate as the Dw rate increased, the overall effect of 2 wk exposure to anoxia was an increase in Dtot rate. Nitrification was enhanced in the manipulated sediment compared to natural conditions, despite anoxia. Anoxia quickly caused a release of dissolved P from its 2 most labile forms. The effect was readily reversible, but in nature the replenishment of oxygen stores is usually linked to an intense mixing of the water column, and it is possible that part of the P released during anoxia reaches the productive layer. In our experiments, anoxia affected P cycling more than N cycling.
  • Gaillard, M. -J.; Sugita, S.; Mazier, F.; Trondman, A. -K.; Brostrom, A.; Hickler, T.; Kaplan, J. O.; Kjellstrom, E.; Kokfelt, U.; Kunes, P.; Lemmen, C.; Miller, P.; Olofsson, J.; Poska, A.; Rundgren, M.; Smith, B.; Strandberg, G.; Fyfe, R.; Nielsen, A. B.; Alenius, T.; Balakauskas, L.; Barnekow, L.; Birks, H. J. B.; Bjune, A.; Bjorkman, L.; Giesecke, T.; Hjelle, K.; Kalnina, L.; Kangur, M.; van der Knaap, W. O.; Koff, T.; Lageras, P.; Latalowa, M.; Leydet, M.; Lechterbeck, J.; Lindbladh, M.; Odgaard, B.; Peglar, S.; Segerstrom, U.; von Stedingk, H.; Seppä, H. (2010)
  • Conley, Daniel J; Björk, Svante; Bonsdorff, Erik; Carstensen, Jacob; Destouni, Georgia; Gustafsson, Bo G; Hietanen, Susanna; Kortekaas, Marloes; Kuosa, Harri; Meier, H. E. Markus; Muller-Karulis, Baerbel; Nordberg, Kjell; Norkko, Alf; Nurnberg, Gertrud; Pitkänen, Heikki; Rabalais, Nancy N; Rosenberg, Rutger; Savchuk, Oleg P; Slomp, Caroline P; Voss, Maren; Wulff, Fredrik; Zillen, Lovisa (2009)
    Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in bottom waters, are important constraints on the formation and maintenance of hypoxia. Climate controlled inflows of saline water from the North Sea through the Danish Straits is a critical controlling factor governing the spatial extent and duration of hypoxia. Hypoxia regulates the biogeochemical cycles of both phosphorus (P) and nitrogen (N) in the water column and sediments. Significant amounts of P are currently released from sediments, an order of magnitude larger than anthropogenic inputs. The Baltic Sea is unique for coastal marine ecosystems experiencing N losses in hypoxic waters below the halocline. Although benthic communities in the Baltic Sea are naturally constrained by salinity gradients, hypoxia has resulted in habitat loss over vast areas and the elimination of benthic fauna, and has severely disrupted benthic food webs. Nutrient load reductions are needed to reduce the extent, severity, and effects of hypoxia.
  • Arppe, Laura (University of Helsinki, 2009)
    Publications of the Department of Geology. D.
  • Heinonen, Jussi S.; Luttinen, Arto V. (2008)
    "Ferropicrites and their differentiates make up a geochemically distinctive group of dikes that crosscut Jurassic continental flood basalts of the Karoo large igneous province at Vestfjella, western Dronning Maud Land. Antarctica. The Vestfjella ferropicrites can be divided into two geochemical types: The depleted ferropicrites have (La/Sm)(N) of 1.2-1.3, (Sm/Yb)(N) of 4.5, initial epsilon(Nd) from +7 to +8, initial epsilon(Sr) from -18 to -19, and show relative depletion of highly incompatible elements, but pronounced enrichment of V; The enriched ferropicrites have (La/Sm)(N) of 1.7, (Sm/Yb)(N) of 5.1-5.4, initial epsilon(Nd) from +3 to +4, initial epsilon(Sr) from 0 to + 1, and show general enrichment of incompatible trace elements. The immobile incompatible element signatures of the ferropicrites have not been significantly affected by alteration, fractional crystallization, or contamination. Based on primitive olivine phenocrysts (Fo(79-88)) and high epsilon(Nd) values, the depleted ferropicrites represent near-primary melts derived from anomalous hot mantle sources. Overall, geochemical compositions favor a pyroxenite source for the ferropicrites. Unusually high (V/Lu)(N) values of the depleted ferropicrites indicate an affinity to oceanic Fe-Ti gabbros and geochemical modeling favors such a recycled mantle source component in them. The enriched ferropicrites probably represent near-primary melts, but this cannot be confirmed. They may also record an exceptionally Fe-rich source component, but their high Fe contents stem at least partly from relatively low-degree melting at high pressures, as indicated by the high (La/Sm)(N) and (Sm/Yb)(N) rados. Examination of a global ferropicrite dataset reveals that the recycled Fe-Ti gabbro component is detectable in many ferropicrites. (C) 2008 Elsevier B.V. All rights reserved."
  • Suutari, Milla; Majaneva, Markus; Fewer, David Peter; Voirin, Bryson; Aiello, Annette; Friedl, Thomas; Chiarello, Adriano G; Blomster, Jaanika (2010)
  • Hietanen, Susanna; Kuparinen, Jorma (2008)
    Benthic processes were measured at a coastal deposition area in the northern Baltic Sea, covering all seasons. The N-2 production rates, 90-400 mu mol N m(-2) d(-1), were highest in autumn-early winter and lowest in spring. Heterotrophic bacterial production peaked unexpectedly late in the year, indicating that in addition to the temperature, the availability of carbon compounds suitable for the heterotrophic bacteria also plays a major role in regulating the denitrification rate. Anaerobic ammonium oxidation (anammox) was measured in spring and autumn and contributed 10% and 15%, respectively, to the total N-2 production. The low percentage did, however, result in a significant error in the total N-2 production rate estimate, calculated using the isotope pairing technique. Anammox must be taken into account in the Gulf of Finland in future sediment nitrogen cycling research.