Browsing by Subject "annual cycle"

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  • Kolari, Pasi; Chan, Tommy; Porcar-Castell, Albert; Back, Jaana; Nikinmaa, Eero; Juurola, Eija (2014)
  • Yang, Yu; Zhijun, Li; Leppäranta, Matti; Cheng, Bin; Shi, Liqiong; Lei, Ruibo (2016)
    Landfast sea ice forms and remains fixed along the coast for most of its life time. In Prydz Bay, landfast ice is seasonal due to melting, mechanical breakage and drift of ice in summer. Its annual cycle of thickness and temperature was examined using a one-dimensional thermodynamic model. Model calibration was made for March 2006 to March 2007 with forcing based on the Chinese National Antarctic Research Expedition data, which consisted of in situ ice and snow observations and meteorological records at the Zhongshan Station. The observed maximum annual ice thickness was 1.74 m. The ice broke and drifted out in summer when its thickness was 0.5-1.0 m. Oceanic heat flux was estimated by tuning the model with observed ice thickness. In the growth season, it decreased from 25 Wm(-2) to 5W m(-2), and in summer it recovered back to 25 W m(-2). Albedo was important in summer; by model tuning the estimated value was 0.6, consistent with the ice surface being bare all summer. Snow cover was thin, having a minor role. The results can be used to further our understanding of the importance of landfast ice in Antarctica for climate research and high-resolution ice-ocean modelling.
  • Korpilahti, Eeva (Suomen metsätieteellinen seura, 1988)
    Data were collected over 3 yr during the growing season in a 20-yr-old stand at the Forestry Field Station of the University of Helsinki, Finland, to study the relations of photosynthesis and transpiration to environmental factors (irradiance, temperature, water content of soil and air) and metabolic processes.
  • Haraguchi, Lumi; Moestrup, Øjvind; Jakobsen, Hans Henrik; Lundholm, Nina (International Phycological Society, 2022)
    Phycologia
    Identification of planktonic flagellates is challenging, and multiple species are often lumped together, limiting our understanding of their diversity and ecology. Our aim was to investigate changes in the phytoplankton community composition over the annual cycle in Roskilde Fjord, Denmark, focusing on the identification of organisms smaller than 20 µm. Weekly microscope and pigment data indicated a low contribution of diatoms and dinoflagellates and the importance of cryptophytes, euglenophytes and green algae, with high contributions of alloxanthin and chlorophyll b. Community composition using Serial Dilution Cultures (SDC) confirmed the high contribution of cryptophytes, prasinophytes and euglenophytes in the phytoplankton community. In contrast, diatoms only played a minor role. Seasonal changes were observed within cryptophytes, with Teleaulax dominance during cold months shifting to Hemiselmis in summer. Small prasinophytes and pico-eukaryotes were always present but had a low relative contribution to the total phytoplankton biomass. Cultured organisms enabled the identification of Hemiselmis cf. cryptochromatica, recorded for the first time in European waters, and an undescribed Pyramimonas species. We describe the new species as Pyramimonas octopora sp. nov., placed within Pyramimonas subg. Vestigiferae, based on morphological and molecular (SSU rDNA) data. The distinctive features of the new species are the eight irregularly rounded perforations arranged in a square box with rounded corners around the centre of the base plate of the box scales, and the complex crown scales, not observed in previously described Pyramimonas species.
  • Luomajoki, Alpo (Suomen metsätieteellinen seura, 1986)
    A study of 16 tree species showed that, including yearly and latitudinal variation, the tetrad phase was reached from late March to early June in conifers and Populus tremula (correlated with heat sums) and in late July to mid-Aug. in Betulaceae (correlated with daylength). These differences were thought to be associated with seasonal adaptive strategies rather than taxonomic relationships.
  • Leisiö, Larisa; Lublinskaya, Marina (Helsingin yliopiston kirjasto, 2022)
    In this paper we discuss the names of the periods of the annual cycle of the Northern Samoyeds, the words for year, the seasons and the months. We show that these names are nature-centered and that the symbiosis with nature was the basis of life and livelihood of the Northern Samoyeds.