CH4 production and oxidation processes in a boreal fen ecosystem after long‐term water table drawdown

Fens, which extend over vast areas in the Northern hemisphere, are sources of the greenhouse gas CH₄. Climate change scenarios predict a lowering water table (WT) in mires. To study the effect of WT drawdown on CH₄ dynamics in a fen ecosystem, we took advantage of a WT drawdown gradient near a ground water extraction plant. Methane fluxes and CH₄ production and oxidation potentials were related to microbial communities responsible for the processes in four mire locations (wet, semiwet, semidry, and dry). Principal component analyses performed on the vegetation, pH, CH₄, and WT results clearly separated the four sampling locations in the gradient. Long‐term lowering of WT was associated with decreased coverage of Sphagnum and aerenchymatic plants, decreased CH₄ field emissions and CH₄ production potential. Based on mcrA terminal restriction fragment length polymorphism the methanogen community structure correlated best with the methane production and coverage of aerenchymatic plants along the gradient. Methanosarcinaceae and Methanocellales were found at the pristine wet end of the gradient, whereas the Fen cluster characterized the dry end. The methane‐oxidizing bacterial community consisted exclusively of Methylocystis bacteria, but interestingly of five different alleles (T, S, R, M, and O) of the particulate methane monooxygenase marker gene pmoA. The M allele was dominant in the wet locations, and the occurrence of alleles O, S, and T increased with drainage. The occurrence of the R allele that characterized the upper peat layer correlated with CH₄ oxidation potential. These results advance our understanding of mire dynamics after long‐term WT drawdown and of the microbiological bases of methane emissions from mires.     

Transplantation of organic surface horizons of boreal soils into warmer regions alters microbiology but not the temperature sensitivity of decomposition

Changes in soil carbon, the largest terrestrial carbon pool, are critical for the global carbon cycle, atmospheric CO₂ levels and climate. Climate warming is predicted to be most pronounced in the northern regions and therefore the large soil carbon pool residing in boreal forests will be subject to larger global warming impact than soil carbon pools in the temperate or the tropical forest. A major uncertainty in current estimates of the terrestrial carbon balance is related to decomposition of soil organic matter (SOM). We hypothesized that when soils are exposed to warmer climate the structure of the ground vegetation will change much more rapidly than the dominant tree species. This change will alter the quality and amount of litter input to the soil and induce changes in microbial communities, thus possibly altering the temperature sensitivity of SOM decomposition. We transferred organic surface soil sections from the northern borders of the boreal forest zone to corresponding forest sites in the southern borders of the boreal forest zone and studied the effects of warmer climate after an adaptation period of 2 years. The results showed that initially ground vegetation and soil microbial community structure and community functions were different in northern and southern forest sites and that 2 years of exposure to warmer climate was long enough to cause changes in these ecological indicators. The rate of SOM decomposition was approximately equally sensitive to temperature irrespective of changes in vegetation or microbial communities in the studied forest sites. However, as temperature sensitivity of the decomposition increases with decreasing temperature regime, the proportional increase in the decomposition rate in northern latitudes could lead to significant carbon losses from the soils.     

Cultivation of a perennial grass for bioenergy on a boreal organic soil – carbon sink or source?

The area under the cultivation of perennial bioenergy crops on organic soils in the northern countries is fast increasing. To understand the impact of reed canary grass (RCG, Phalaris arundinaceae L.) cultivation on the carbon dioxide (CO₂) balance of an organic soil, net ecosystem CO₂ exchange (NEE) was measured for four years in a RCG cultivated cutover peatland in eastern Finland using the eddy covariance technique. There were striking differences among the years in the annual precipitation. The annual precipitation was higher during 2004 and 2007 and lower during 2005 and 2006 than the 1971–2000 regional mean. During wet growing seasons, moderate temperatures, high surface soil moisture and low evaporative demand favoured high CO₂ uptake. During dry seasons, owing to soil moisture and atmospheric stress, photosynthetic activity was severely restricted. The CO₂ uptake [gross primary productivity (GPP)] was positively correlated with soil moisture, air temperature and inversely with vapour pressure deficit. Total ecosystem respiration (TER) increased with increasing soil temperature but decreased with increasing soil moisture. The relative responses of GPP and TER to moisture stress were different. While changes in TER for a given change in soil moisture were moderate, variations in GPP were drastic. Also, the seasonal variations in TER were not as conspicuous as those in GPP implying that GPP is the primary regulator of the interannual variability in NEE in this ecosystem. The ecosystem accumulated a total of 398 g C m^?2 from the beginning of 2004 until the end of 2007. It retained some carbon during a wet year such as 2004 even after accounting for the loss of carbon in the form of harvested biomass. Based on this CO₂ balance analysis, RCG cultivation is found to be a promising after‐use option on an organic soil.     

Breeding success of ducks in relation to different habitat factors

Breeding success of four duck species, Teal Anas crecca , Mallard Anas platyrhynchos , Wigeon Anas penelope and Goldeneye Bucephala clangula , was studied in a boreal watershed in southern Finland during 1988–1991 in relation to habitat type (based on vegetation development) and food abundance. Of the three common breeders, breeding success (broods/ pair) was highest in Teal (1.7) and lower in Mallard (1.4) and Goldeneye (1.2). Over the years, Goldeneye brood densities were less variable than were pair densities, so breeding success varied more among years that did that of Mallard or Teal. In Teal, the yearly numbers of pairs and broods fluctuated together, whereas in Mallard neither varied appreciably. Breeding success by Goldeneye was higher where nektonic invertebrates were more abundant, whereas breeding success of the dabbling ducks had very few significant correlations with environmental factors.     

Visual conditions and habitat shape the coloration of the Eurasian perch (Perca fluviatilis L.): a trade‐off between camouflage and communication?

In theory, selection for effective camouflage (i.e. dull coloration) in fish should be strongest when the conditions for visual predation are most favourable, such as in structurally simple pelagic habitats. By contrast, in more sheltered (e.g. littoral) habitats, selection may favour effective intra‐specific communication (i.e. bright coloration) (at the expense of crypsis). Poor transparency, as in highly humic waters, should constrain colour adaptations. We investigated phenotypic variation in body coloration of Eurasian perch (Perca fluviatilis L.) in littoral and pelagic habitats of four humic boreal lakes. Perch from the most transparent lake had the lightest and less coloured belly and perch were more colourful in the littoral habitats than in the pelagic areas, with the pattern being clearest in the most transparent lake. In addition, perch in the most transparent lake exhibited sexual dichromatism, with males having a more colourful belly than the females, whereas no indications of sexual dichromatism were found in more humic lakes. Moreover, in the most transparent lake, the condition of fish correlated with bright belly coloration in the littoral, but with dull belly coloration in the pelagic habitat. The results obtained in the present study suggest that selection on perch coloration may differ between lakes as a result of visual properties of the water, and within lakes as a result of divergent selection for camouflage and communication in pelagic and littoral habitats. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 47–59.     

Offspring performance is linked to parental identity and male breeding ornamentation in whitefish

The 'good genes' hypothesis predicts that males advertise their quality with different sexual ornaments and that females are able to recognize the genetic quality of males by evaluating these characteristics. In the present study, we investigated the parental effects on offspring performance (feeding and swimming ability of newly-hatched larvae) and examined whether male ornamentation indicates offspring success in performance trials of whitefish ( Coregonus lavaretus Linnaeus). Offspring first-feeding success had a strong paternal effect and it was also positively correlated with the size of male breeding tubercles, indicating that breeding ornamentation of males can function as an honest indicator of their genetic quality. In addition, the observed positive correlation between male tubercle size and condition factor suggests that highly ornamented males are efficient foragers and that this trait may have a heritable basis. By contrast to feeding success, only a maternal effect was found in the swimming ability of the larvae. Clear family-specific differences observed in both measures of performance strongly suggest that parental identity may have important effects on larval survival in the wild.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 532–539.