Artikkelit jotka sisältää sanan 'ecology'

The effects of substrate concentrations on temperature sensitivity of methanogenesis and butyrate metabolism was investigated in sediment slurries from a permanently waterlogged swamp. Temperature sensitivity decreased with decreasing substrate concentrations parallelling results obtained with axenic methanogenic cultures. H2 concentrations decreased with decreasing temperatures while the concentration of volatile fatty acids remained fairly unaffected by incubation temperature. The possibility of butyrate metabolism at in situ conditions was verified by temperature compensated thermodynamic calculations. Key words: Methanogenesis, microbiology, wetland ecology

• Westermann, Dept. of General Microbiology, Univ. of Copenhagen, Solvegaden 83H, DK-1307 Copenhagen K, Denmark Sähköposti: ei.tietoa@nn.oo

Cushions of Sphagnum fuscum and S. angustifolium were grown in the laboratory in four different C02 concentrations (350, 700, 1 000, and 2 000 ppm) and N deposition levels (0, 10, 30, and 100 kg ha-1 a-1). The same N deposition levels were also applied in the field. C02 concentration increased both the shoot density and dry mass of S. fuscum but decreased the length increment. There was no net effect on production. For S. angustifolium, shoot density did not alter with elevated C02 con-centration but the C02 induced increment in dry mass and length caused increased production. S. angustifolium suffered from nutrient deficiency on the 0 kg N ha-1a-1 treatment and S. fuscum had difficulties to survive at the heaviest N load. No clear trends in length increment or cover was noticed in the field study during the first year. Keywords: Bryophyte ecology, climate change, peatlands, production

• Jauhiainen, University of Joensuu, Department of Biology, P.O. Box 111, FIN-80I0I Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
• Vasander, Sähköposti: ei.tietoa@nn.oo
• Silvola, Sähköposti: ei.tietoa@nn.oo

Two main factors control the rates of methane production in peat (in senso microbial formation of methane): the water table level and the chemical characteristics of the peat material. The water table restricts oxygen penetration into the peat because of the much slower diffusion of gases in water compared to gaseous phases. The oxygen distribution will govern the location of the strictly anaerobic, methanogenic bacteria in the peat profile. The degree of waterlogging will also influence the availability of the peat plant material for microbial decomposition, when it reaches the anaerobic zone. In waterlogged environments, the surface litter will quickly enter anoxic conditions. In such environments, high methane formation potentials are often found in the uppermost peat layers. Where the water table is positioned further down in the peat profile, a higher proportion of the easily degradable compounds are degraded under oxic conditions and therefore gone by the time the litter enters the anoxic layers. Lignified organic matter reaching the anaerobic zone will be little further degraded. This effect is most likely to be compounded if the nitrogen content of the litter is low. The net flux of methane from peat surfaces is highly dependent on the extent of microbial methane oxidation in the peat profile. Methane oxidizing bacteria need oxygen for the primary oxidation of methane and for their oxygen dependent respiration. The oxygen distribution, and hence the water table position, will therefore also affect the activity of the methanotrophic bacteria. Typically, highest methane oxidation activity is found around the most frequent position of the water table. At this level, high concentrations of methane meet oxygen diffusing down from the peat surface. Methane oxidation potentials in peat have been observed to correlate with the level of the water table, the concentration of methane just below this level, and in some sub-habitats, with the emissions of methane. Field studies have also shown that comparatively dry environments with fluctuating water table levels may act as sinks as well as sources for atmospheric methane. Some habitats show diurnal rhythms, with higher emissions during night. This is probably due to temperature limitation of the methanotrophic bacteria during the night. Keywords: Carbon flow, methanogenic bacteria, methanotrophic bacteria, mire ecology

• Svensson, Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, S-750 07 Uppsala, Sweden Sähköposti: ei.tietoa@nn.oo
• Sundh, Sähköposti: ei.tietoa@nn.oo

The relations between Sphagnum species, vegetation, and the macrotopographical and microtopographical environmental gradients of a plateau bog located on the southern coast of Finland were studied. A profile was levelled from the mire margin to the mire centre and 16 sample plots were located along the profile. The vegetation of each sample plot was described using coverage percentages. The mire water level, pH, and specific conductivity were measured for each plot. Samples of the capitula of different species of Sphagnum were taken and they were measured for water content. Hummock surfaces were predominant in the mire centre. The hollows were relatively dry ombrotrophic small sedge bogs. The mire margin fen was mostly mesotrophic. In the northern part of the mire there was also a eutrophic flark fen. In the mire centre the pH was 4 or less and the specific conductivity ranged from 10 to 25 µS/cm. In the mire margin fen the pH ranged from 4.7 to 5.7 and the specific conductivity was c. 50 µS/cm. The water content of the capitula of the Sphagna was in general high, ranging from 300 to 3000 %. In the hollows of the mire centre the water content of Sphagnum tenellum was as low as 15 %. Key words: mire vegetation, ecology, plateau bog, water content, Sphagnum.

• Heikkilä, Department of Geography, University of Helsinki, Hallituskatu 11, SF-00100 Helsinki, Finland Sähköposti: ei.tietoa@nn.oo
• Löytönen, Sähköposti: ei.tietoa@nn.oo