Artikkelit jotka sisältää sanan 'global change'

Jari Huttunen, Hannu Nykänen, Jukka Turunen, Olli Nenonen, Pertti Martikainen. Typpioksiduulivirrat suunnitellun Vuotoksen tekojärven alueen soilta.
English title: Fluxes of nitrous oxide on natural peatlands in Vuotos, an area projected for a hydroelectric reservoir in northern Finland.
Avainsanat: global change; Northern boreal peatlands; climate warming; flooding; greenhouse gas emission; hydro dam
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Nitrous oxide (N2O) fluxes were measured on ten natural minerotrophic peatlands in an area planned for a hydroelectric reservoir (Vuotos) in northern Finland. The mean N2O fluxes from the sites with mean water tables from –25 to 3.4 cm (negative below the peat surface) ranged from –30 to 230 µg m–2 d–1 during summer 1994. At the driest site, the herb-grass spruce mire with the mean water table at –38 cm, the mean summertime N2O emission was 940 µg m-2 d-1 in 1994, attributable to the increased N2O release at low peat temperatures in autumn. A similar increase in the N2O emissions was not found in 1995, as the measurements were finished before the peat started to freeze. The mean N2O fluxes at the sites correlated negatively with the mean water table levels. The peatlands in the northern boreal zone are unlikely important sources of atmospheric N2O in their natural state. The planned reservoir would barely have large long-term N2O emissions from the pelagic zone, but the importance of temporally flooded areas in the postflood N2O release is uncertain similar to the short-term emissions following the flooding.
  • Huttunen, Research and Development Unit of Environmental Health, Department of Environmental Sciences, Bioteknia 2, University of Kuopio, PO Box 1627, FIN-70211 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Nykänen, Sähköposti: ei.tietoa@nn.oo
  • Turunen, Sähköposti: ei.tietoa@nn.oo
  • Nenonen, Sähköposti: ei.tietoa@nn.oo
  • Martikainen, Sähköposti: ei.tietoa@nn.oo
Patrick Crill, Karen Bartlett, Nigel Roulet. Methane flux from boreal peat-lands.
Avainsanat: global change; Carbon; climate change
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The peatlands found in the boreal zone (roughly 45°-60°N) store a significant reservoir of carbon, much of which is potentially available for exchange with the atmosphere. The anaerobic conditions that cause these soils to accumulate carbon also makes wet, boreal peatlands significant sources of methane (CH4) to the global troposphere. We estimate that boreal wetlands contribute approximately 19.5 Tg CH4 yr-1. The data available on the magnitude of boreal CH4 emissions have rapidly accumulated in the past twenty years. This paper offers a short review of the flux measurements (which range from roughly I to 2 000 mg CH4 m-2 d-1'), considers environmental controls of the flux and briefly discusses how climate change might affect future fluxes. Keywords: Carbon, climate change, global change
  • Crill, Complex Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, New Hampshire, U.S.A. 03824 Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Bartlett, Sähköposti: ei.tietoa@nn.oo
  • Roulet, Sähköposti: ei.tietoa@nn.oo
Elon S. Verry, Noel R. Urban. Nutrient cycling at Marcell Bog, Minnesota.
Avainsanat: Minnesota; peatlands; global change; Carbon cycling; nutrient budgets
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Fourteen kg ha-1 yr-1 of N enter the mire acrotelm, and 12 are sequestered in the catotelm peat. However, 66 kg ha-1 yr-1 cycle between plant growth and decay in the acrotelm each year, primarily as ammonium and organic N. Fifty eight percent of the sulfate inputs to the mire are retained, but the export of organic sulfur (1.5 kg ha-1 yr-1) yields a total sulfur retention of 37%. As with N, recycling within the acrotelm and vegetation layer is large (12.5 kg ha-1 yr-1). The proton cycle in the mire is dominated by nutrient uptake and plant decay (about 80% of the 1 044 meq m-2 yr-1). Organic acid production is the major source of free acidity (263 meq m-2 yr-1) and buffers the water near pH 4. About half of the metals entering the mire are retained, and about 60% of the P is retained. Retention of P is particularly high (about 80%) during the spring snowmelt season. The carbon cycle at the Marcell mire consists of about 655 g C m-2 yr-1entering and leaving the acrotelm and vegetation. Eighteen to 28 g C m-2 yr-1are sequestered each year in the catotelm (true and apparent rate of accumulation). Net primary production in the moss, tree, and herbaceous layers accounts for about 385 g C m-2 yr-1, while C02 losses in soil and plant respiration account for about 589g C m-2 yr-1. Root net primary productivity (unmeasured) is estimated at 152 g C m-2 yr-1. Water export of C is 37 and methane losses are about 6 g C m-2 yr-1. Keywords: Carbon cycling, global change, Minnesota, nutrient budgets, peatlands
  • Verry, USD A- Forest Service, North Central Forest Exp. Stn., 1831 Highway 169 East, Grand Rapids, MN, USA. Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Urban, Sähköposti: ei.tietoa@nn.oo
Eville Gorham, Jan A. Janssens. The paleorecord of geochemistry and hydrology in northern peatlands and its relation to global change.
Avainsanat: peatlands; Geochemistry; global change; hydrology; paleorecord
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Evidence is presented to show the utility of peatland paleorecords in determining (1) variations in the time of initiation as well as the rate of accumulation of peat and biophilic elements, (2) the history of changes in surface-water acidity and water-table depth, (3) shifts in ground-water influence upon plant communities and the chemistry of the water in which they grow, and (4) alterations in the rate of deposition of diverse pollutants from the atmosphere. This evidence constitutes background information of great value for investigations of the ecological and biogeochemical consequences of global change. Keywords: Geochemistry, global change, hydrology, paleorecord, peatlands
  • Gorham, Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, U.S.A. Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Janssens, Sähköposti: ei.tietoa@nn.oo

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