Suo - Mires and peat

Paavo Ojanen. Metsäojituksen vaikutuksesta ilmastoon.

English title: Climatic impacts of forestry on drained boreal peatlands.

Original keywords: turvemaa; ojitus; hiilidioksidi; metaani; kasvihuonekaasut; typpioksiduuli; suometsätalous

English keywords: peat; peatland forestry; ditching; Carbon dioxide; methane; nitrous oxide; greenhouse gases

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Metsäojitus vähentää merkittävästi soiden metaanipäästöjä. Rehevien ruoho- ja mustikkaturvekankaiden maaperä on kuitenkin merkittävä hiilidioksidin lähde ilmakehään turpeen vähenemisen takia. Karujen puolukka- ja varputurvekankaiden turve ei näyttäisi nykyisin merkittävästi vähenevän. Puustobiomassan merkittävän suurenemisen ansiosta Suomen metsäojitetut suot ovat tällä hetkellä kasvihuonekaasujen nettonielu. Ilmastonmuutoksen hillitsemisen kannalta metsänkasvatuksen jatkaminen lienee paras maankäyttömuoto metsäojitetuille soille lähivuosikymmenten aikana. Vaikka laajamittaisella ennallistamisella voitaisiin estää rehevien soiden turpeen väheneminen, samalla kuitenkin puuston kasvu vähenisi ja metaanipäästö kasvaisi. Ennallistamisen jälkeen kestänee vähintään kymmeniä tai satoja vuosia, ennen kuin saavutetaan ilmaston kannalta metsänkasvatuksen jatkamista parempi tilanne. Pitkällä aikavälillä rehevien soiden ennallistaminen on kuitenkin ilmaston kannalta parempi vaihtoehto, koska jo muutaman kymmenen senttimetrin paksuisen turvekerroksen häviäminen vapauttaa enemmän hiiltä ilmakehään kuin kookaskaan puusto pystyy sitomaan itseensä. Metsäojitettujen soiden kasvihuonekaasutaseista on viime vuosina kertynyt melko kattavasti tietoa. Jotta metsätalouden jatkamisen tai mahdollisen puuston kasvamaan jättämisen tai suon ennallistamisen ilmastovaikutuksen suuruutta voidaan täsmällisesti arvioida, tarvitaan vertailulaskelmia eri vaihtoehtojen kasvihuonekaasupäästöistä. Suuren kokonaispinta-alan takia metsäojitettujen soiden tulevalla käytöllä voi olla suuri vaikutus Suomen kasvihuonekaasupäästöihin.

Ojanen, Luonnonvarakeskus (LUKE) Sähköposti: paavo.ojanen@helsinki.fi

Kimmo Tolonen, Markku Suoknuuti. Keidassuon pintakuvioituksen muutokset viimeisten 82 vuoden aikana Pyhtään Munasuolla.

English title: Changes in the surface patterning in the raised bog Munasuo, SE Finland during the past 82 years.

Original keywords: keidassuo; kermi; kulju; allikko; ruoppakulju; välipinta; progressiivinen kehitys; ilmaston muutos; hiilen sidonta

English keywords: raised bog; mud-bottom hollow; mud-bottom pool; carbon sequestration; hummock ridge; progressive development of mire

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Työssä tarkastellaan tyypillisen kaakkoissuomalaisen laakiokeitaan, Pyhtään Munasuon, kasvillisuuden ja pintarakenteiden muutoksia 82 vuoden ajanjaksolla 1941–2022. Aineisto perustuu ilmakuviin ja maastohavaintoihin. Täydennyksenä esitetään muutamia havaintoja myös Munasuon itäpuolisen Valkmusan-Kananiemensuon suokompleksin alueelta. Pohdimme tekijöitä, jotka mahdollisesti selittävät havaittuja muutoksia. Työmme liittyy ajankohtaiseen tutkimukseen, jossa selvitetään ilmastonmuutoksen vaikutuksia soiden kasvillisuuteen.
Työssä käytetty ImageJ-ohjelmisto osoittautui käyttökelpoiseksi työkaluksi suoallikoiden, ruoppakuljujen ja keidassuon pintarakenteiden, kuljujen ja mättäiden, sekä suurempien puiden havaitsemiseen ilmakuvissa. Pintatopografiassa mättäät ja kermit osoittautuivat varsin pysyviksi, kun taas kuljuissa, ruoppakuljuissa ja allikoissa oli enemmän vaihtelua. Mättäiden rahkasammalten, erityisesti rusorahkasammalen (Sphagnum rubellum) suhteellisen peittävyyden lisääntyminen kuljusammallajiston kustannuksella sekä allikoiden avovesipinnan nopea pienentyminen saattaa osaltaan ilmentää hiilensidonnan merkittävää viimeaikaista kasvua Munasuon keidassuoekosysteemissä.

Tolonen, Sepänkatu 4 as 2, 24240 Salo Sähköposti: kimmotolonen38@gmail.com
Suoknuuti, Heinäkorvenkuja 146, 48910 Kotka Sähköposti: markku.suoknuuti@kymp.net

Mirva Leppälä, Anna M. Laine, Eeva-Stiina Tuittila. Talviaikainen hiilivuo boreaaliselta suosukkessiogradientilta seuraa kesäaikaisen hiilidynamiikan vaihtelua.

English title: Winter carbon losses from a boreal mire succession sequence follow summertime patterns in carbon dynamics.

Original keywords: sukkessio; suon kehitys; primaarisoistuminen; hiilidioksidi; metaani; lumikerros; Siikajoki; maankohoamisrannikko

English keywords: Carbon dioxide; methane; Mire development; land uplift coast; mire succession; primary paludification; snow pack; Siikajoki

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Although carbon (C) gas exchange during the summer largely determines the annual C balance of mires, the wintertime fluxes cannot be ignored. Decomposition continues as long as the soil is not frozen and a proportion of the gases produced during summer are also released during winter. We measured carbon dioxide (CO2) and methane (CH4) fluxes along a successional mire sequence during two winters following growing seasons with divergent weather conditions. We studied the successional trends in wintertime C release in boreal mires, and quantified the contribution of wintertime C fluxes to annual fluxes. Wintertime CO2 and CH4 fluxes from the successional mire sequence were related to the flux rates during the previous summer. Average winter CO2 release along the successional sequence varied between 19.5 and 44.9 g CO2-C m–2 winter–1(6-months), and accounted for 8–14% of the annual CO2 release. There was no clear successional trend in CO2 fluxes. Average winter CH4 release along the successional sequence varied between 0.20 and 7.29 CH4-C g m–2 winter–1(6-months).The winter CH4 fluxes accounted for up to 38% of the annual CH4 emissions. Occasional CH4 uptake was detected at the younger successional stages during winter following the dry summer, while after the wet summer all sites emitted CH4. In general, most of the winter C losses were composed of CO2.

Leppälä, Mirva Leppälä, Finnish Forest Research Institute, FIN-91500 Muhos, Finland. Current address: Metsähallitus, Natural Heritage Services Ostrobothnia, BOX 81, FI-90101 Oulu, Finland, email: mirva.leppala@metsa.fi Sähköposti: ei.tietoa@nn.oo
Laine, Sähköposti: ei.tietoa@nn.oo
Tuittila, Sähköposti: ei.tietoa@nn.oo

Markku Mäkilä, Tomasz Goslar. Etelä- ja keskiboreaalisten soiden pintakerroksen hiilidynamiikka.

English title: The carbon dynamics of surface peat layers in southern and central boreal mires of Finland and Russian Karelia.

Avainsanat: Finland; peatland; Acrotelm; peat accumulation; carbon pool; turnover

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The carbon pool of surface layers (up to 500 years old) in 73 boreal mires was investigated in order to assess its significance in the carbon cycle. Peat columns were collected from mires of varying depth, age and degree of natural state in the aapa mire and raised bog regions and coastal mires of southern and central Finland and Russian Karelia. The quantities of carbon sequestered during recent centuries and over the entire lifetimes of the mires were determined using a total of 367 dates (186 14C AMS and 181 conventional dates) and age-depth models derived from bulk density measurements. Particular attention was paid to accumulation over the last 100 and 300 years, as these periods encompass the best estimates of the acrotelm age across the range of sites investigated. The average carbon pool of layers younger than 300 years was determined as 101 ± 8 tonnes ha-1 in the aapa mire region, 115 ± 9 tonnes ha-1 in the raised bog region and 184 ± 20 tonnes ha-1 in coastal mires. Overall, the mean carbon pool of layers younger than 300 years was calculated to be 121 ± 7 tonnes ha-1 (range 44–259 tonnes ha-1) and of layers younger than 100 years 63 ± 4 tonnes ha-1 (range 17–141 tonnes ha-1). The size and dynamics of the carbon pool represented by these surface layers depends upon the mire site type, vegetation and natural state; variations reflect differences in plant communities as well as factors that affect biomass production and decay rates. The high carbon accumulation in surface layers is temporary and mainly related to the development of the mire. The surface layers are still undergoing a rapid carbon cycle. A relatively rapid accumulation and turnover of carbon is taking place in surface layers (<300 years) in the same way as in a growing forest. Therefore, this "pre-peat" in the surface layers of mires should be distinguished as a separate class from the peat underneath. Our results indicate how important it is to understand the carbon accumulation rates of surface layers and the long-term dynamics of mire carbon accumulation in order to set the current flux estimates in perspective.

Mäkilä, Geological Survey of Finland, P.O. Box, 96, 02151 Espoo, Finland Sähköposti: ei.tietoa@nn.oo
Goslar, Sähköposti: ei.tietoa@nn.oo

Jukka Turunen. Luonnontilaisten soiden pitkänajan- ja nykykertymät boreaalisella ja subarktisella kasvillisuusvyöhykkeellä: katsaus.

English title: Past and present carbon accumulation in undisturbed boreal and subarctic mires: a review.

Avainsanat: fens; climate change; carbon accumululation; bogs; boreal region; subarctic region; Holocene

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This review integrates the results from several recent studies on carbon (C) accumulation in undisturbed boreal and subarctic mire ecosystems in Finland, Sweden, Russia, Canada, and USA. Generally, a large variation in the average long-term apparent rate of carbon accumulation (LORCA) has been found among mires based on the mire type, age and geographical location. The differences in LORCA between the raised bog region and the aapa mire regions were found to be significant. The updated LORCA for undrained boreal and subarctic mire regions has been estimated at 13–20 g C m–2 a–1 throughout the Holocene, which is clearly lower than previous estimates for these northern mire regions. The age of the peat column is an important predictor of C accumulation and has to be taken into account when comparing results. The results indicate a rapid mire expansion in southern Finland from ca. 10 500 to 8500 cal. year BP, from 5000 to 3000 cal. year BP and around 2000 cal. year BP. In northern Finland the extensive mire expansion occurred from ca. 10500 to 8000 cal. year BP. The recent apparent rate of C accumulation (RERCA) in boreal and subarctic mire regions over the past 100 to 200 years ranges from 30 to 120 g C m-2 a-1. The future C balance scheme of mires is also briefly discussed. Key words: carbon accumulation, bogs, fens, boreal region, subarctic region, Holocene, climate change

Turunen, Geological Survey of Finland, Kuopio Unit, P.O. Box 1237, 70211 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo

Roy Tomlinson, Laoise Davidson. Estimates of carbon stores in four Northern Irish lowland raised bogs.

Avainsanat: peat bulk density; peat carbon density; peat carbon stores

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Soils store more carbon (C) than does vegetation and in Northern Ireland peat has been estimated to account for about 42% of the soil C store. This estimate, however, was based on incomplete field evidence, including uncertainty on peat depths and peat bulk density. This paper aims to show how the estimate might be improved, taking into account bulk density and carbon density measurement. Trial 3-D models are presented to estimate total C content of individual bogs. Results suggest that C stores in northern Irish lowland raised bogs are lower than previously estimated primarily because of low bulk densities which showed no consistent increase with peat depth. Bulk density varied within and between bog profiles on the same bog and between bogs leading to different estimates of C stores. The research indicates a need for more precise modelling of bogs based on stratigraphy and dating of layers and a need for standardised measurement of peat bulk density and carbon storage. The findings, particularly if they apply to the extensive blanket bog, affect local and national totals of soil C stores and have implications for national policies on increasing/preserving C stores.

Tomlinson, School of Geography, The Queen’s University of Belfast, BT7 1NN, Northern Ireland Sähköposti: ei.tietoa@nn.oo
Davidson, Sähköposti: ei.tietoa@nn.oo

Kimmo Tolonen, Goran Possnert, Högne Jungner, Eloni Sonninen, Jukka Alm. High resolution 14C dating of surface peat using the AMS technique.

Avainsanat: Sphagnum; peatlands; Moss increment dating; radiocarbon

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In an AMS (accelerator mass spectrometric) determination of 14C from moss-increment dated samples from a Sphagnum fuscum hummock, a clear peak representing the time of high 14C activity in the atmosphere due to nuclear bomb tests was found. The 14C activities in the peat profile at deeper levels, corresponding to the period down to 1600 BP, showed similar variations as the atmospheric values. The time-scale obtained from radiocarbon dating fitted well with results from moss-increment counting, pollen analysis and dendrochronological dating of a fire horizon. Using the bomb activity peak, the fraction of carbon emanating from deeper layers and refixed into growing peat was estimated. The fraction of soil carbon dioxide taken up by the contemporary Sphagnum sward was thus found to be in the order of 20%. Keywords: Moss increment dating, peatlands, radiocarbon, Sphagnum

Tolonen, Dept. of Biology, Univ. Joensuu, P.O. Box III, FIN-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
Possnert, Sähköposti: ei.tietoa@nn.oo
Jungner, Sähköposti: ei.tietoa@nn.oo
Sonninen, Sähköposti: ei.tietoa@nn.oo
Alm, Sähköposti: ei.tietoa@nn.oo

Ingvar Sundh, Mats Nilsson, Bo H. Svensson. Depth distribution of methane production and oxidation in a Sphagnum peat bog.

Avainsanat: peatlands; Carbon flow; methane oxidation; methane production

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The anaerobic production and potential aerobic oxidation of methane were assessed in a Sphagnum-dominated peatland in Sweden. Peat from four depths in the 0-40 cm (below the vegetation surface) layer was collected in three different plant communities. The rate measurements were made with peat slurries in flasks. The ratio between the mean production and mean oxidation activities was more than ten-fold higher in the two wetter than in the driest community. The within profiles depth distributions of methanogenic and methane-oxidizing activity were similar, showing that a particular level may act as a net source or a net sink for methane, depending on prevailing environmental conditions (primarily the oxygen distribution). The results also suggest that methane production and consumption processes can occur in anaerobic and aerobic micro-zones in very close proximity to each other. Key words: Carbon flow, methane oxidation, methane production, peatlands

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

Jouko Silvola, Pertti Martikainen, Hannu Nykänen. A mobile automatic gas chromatograph system to measure C02, CH4 and N2O fluxes from soil in the field.

Avainsanat: peatland; Carbon dioxide; methane; Automated measuring; nitrous oxide

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A caravan has been converted into a mobile laboratory for measuring fluxes of C02, CH4 and N2O from the soil in the field. The caravan is equipped with a gas chromatograph fitted with TC-, FI- and EC-detectors, and a PC controlled data logger. The gas collecting chambers can be used up to 50 m from the caravan. The closing and opening of the chambers, as well as the flows of sample gases from chambers to the gas chromatograph, is pneumatically regulated. Simultaneous recordings of temperature, light intensity and the depth of water table are made. The system has been used for two months in 1992, and some preliminary results are presented. Keywords: Automated measuring, carbon dioxide, methane, nitrous oxide, peatland

Silvola, Department of Biology, University of Joensuu, P.O. Box III, FIN-80I0I Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
Martikainen, Sähköposti: ei.tietoa@nn.oo
Nykänen, Sähköposti: ei.tietoa@nn.oo

Jouko Silvola, Alm Jukka, Urpo Ahlholm. The effect of plant roots on C02 release from peat soil.

Avainsanat: Decomposition; Carbon allocation; soil respiration

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The contribution of roots to the release of C02 from peat has been examined in both field and laboratory experiments. In the field experiment, columns of peat were isolated from the surrounding peat and the green parts of the plants were continually removed in order to exhaust the living roots contained within the column. The isolated columns released c. 10-20% less C02 than the reference spots where only the growth of the green parts was restrained. C02 production in isolated columns was thereby reduced mostly in mire site types with largest dwarf shrub root biomass. In the greenhouse experiment, C02 release was c. 36% greater from containers containing willow (Salix phylicifolia) roots than from bare peat reference containers. Keywords: Carbon allocation, decomposition, soil respiration

Silvola, Department of Biology, University of Joensuu, P.O. Box 111, FIN-80J0/ Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
Jukka, Sähköposti: ei.tietoa@nn.oo
Ahlholm, Sähköposti: ei.tietoa@nn.oo

Jukka Laine, Harri Vasander, Antti Puhalainen. A method to estimate the effect of forest drainage on the carbon store of a mire.

Avainsanat: peatland forestry; Carbon stores; Boreal zone

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Mires are sinks for carbon. Drainage enhances the aerobic microbial decomposition of the surface peat, which may transform mires into net sources of carbon to the atmosphere. However, the increase in the growth of the tree stand and consequent fixation of carbon after drainage may be expected to have a compensating effect. The effects of drainage on the carbon stores of a mire are not easy to establish. This paper discusses a method that can be used to assess the changes in cases where part of the mire has been left in the virgin condition. The method is based on bulk density and carbon content profiles measured along a transect running from the undrained part to the drained part of the mire. The carbon store of the peat in each case is calculated for the peat depth in which drainage is considered to have caused changes. The subsidence at each measuring point on the drained side is subtracted from the original peat depth before carbon store calculations. Keywords: Boreal zone, carbon stores, peatland forestry

Laine, Department of Forest Ecology, P.O. Box 24, FIN-00014 University of Helsinki, Finland Sähköposti: ei.tietoa@nn.oo
Vasander, Sähköposti: ei.tietoa@nn.oo
Puhalainen, Sähköposti: ei.tietoa@nn.oo

Pirkko Kortelainen, Sari Saukkonen. Leaching of organic carbon and nitrogen from peatland-dominated catchments.

Avainsanat: peatlands; leaching; hydrology; organic carbon; runoff

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The area of 13 study catchments is 2.5-56.3 km2 and 37-87% of the catchments is covered by peatlands. Ditching intensities varied from 0 to 100%. Median total organic carbon (TOC) in runoff waters from the catchments was 10-30 mg l-1 and median total nitrogen (Ntot) 380-1 000 µg l-1. The annual leaching of TOC and N tot was calculated for five catchments for which daily runoff data was available. The range for mean annual leaching of TOC and Ntot from the catchments was 4 700 to 7 300 kg km-2 a-1 and 190-250 kg km-2 a-1, respectively. The variation between different years was high and annual leaching was closely related to annual runoff. The regional variation in the leaching of TOC and N tot was small compared to the annual variation. Keywords: Hydrology, leaching, organic carbon, peatlands, runoff

Kortelainen, National Board of Waters and the Environment, Water and Environment Research Institute, P.O. Box 250, FlN-00101 Helsinki, Finland S Sähköposti: ei.tietoa@nn.oo
Saukkonen, Sähköposti: ei.tietoa@nn.oo

Daniel J. Charman, Ramon Aravena, Barry G. Warner. Isotope geochemistry of gas and water samples from deep peats in boreal Canada.

Avainsanat: Carbon dioxide; carbon isotopes; methane; tritium; water movement

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A number of determinations of carbon isotopes of gas from deep peats in northern Ontario, Canada are presented, 14C contents of both C02 and CH4 are higher than in adjacent peats indicating younger sources of carbon for their production with transport of these sources or of the gases themselves. High tritium levels indicate the presence of water derived from relatively recent precipitation and hydraulic gradients within the peat show that significant vertical water movement is possible. These preliminary results suggest that the carbon dynamics of boreal peatlands are far more complex than is generally realised. Keywords: Carbon dioxide, carbon isotopes, methane, tritium, water movement

Charman, University of Plymouth, Plymouth, Devon, PL4 8AA. UK Sähköposti: ei.tietoa@nn.oo
Aravena, Sähköposti: ei.tietoa@nn.oo
Warner, Sähköposti: ei.tietoa@nn.oo

A. Russel Anderson, D. Graham Pyatt, Joanne M. Sayers, Stuart R. Blackhall, Helen D. Robinson. Volume and mass budgets of blanket peat in the north of Scotland.

Avainsanat: peatland forestry; Carbon stores; Pinus contorta

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The ground surface was 0.5 m lower under a 22-year-old lodgepole pine (Pinus contorta) plantation than in the adjacent unplanted ride. The peat was much drier beneath the trees than in the ride. The depth of peat under the trees, adjusted so that each layer had the same dry bulk density as the originally equivalent depths in the ride, effectively reversing shrinkage due to drying, was 2 cm greater than our best estimate of its original depth and the depth in the ride was 8 cm greater than in 1966. The original depths, surveyed in 1966 had too large an uncertainty (± 15 cm) for the changes to be significant. Keywords: Carbon stores, peatland forestry, Pinus contorta

Anderson, Forestry Authority, Northern Research Station, Roslin, Midlothian, EH25 9SY, UK Sähköposti: ei.tietoa@nn.oo
Pyatt, Sähköposti: ei.tietoa@nn.oo
Sayers, Sähköposti: ei.tietoa@nn.oo
Blackhall, Sähköposti: ei.tietoa@nn.oo
Robinson, Sähköposti: ei.tietoa@nn.oo

Jukka Alm, Kimmo Tolonen, Harri Vasander. Determination of recent apparent carbon accumulation in peat using dated fire horizons.

Avainsanat: dating; fire; Carbon accumulation; charcoal; dendrochronology

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Two charcoal layers, originating from two forest fires, were found at between 7 and 58 cm in the peat of Lakkasuo mire. Using dendro-chronological techniques and fire scars on Scots pine {Pinus sylvestris L.) stumps, the date when these two layers was deposited could be estimated. The earlier fire swept over the mire about 1780 A.D. and the later fire, which seems to have been limited to the eastern part of Lakkasuo, occurred in 1845 A.D. Knowing the thickness of the peat layer above the dated charcoal layers, its bulk density and carbon content, the rate of carbon accumulation during the last 212-147 years could therefore be calculated for different site types in the Lakkasuo mire complex. These values ranging from 39.8 to 80.7 g C m-2 a-1. can be compared to those (28.5-42.8 g C m-2 a-1 ) 0f the peat layer down to a still older fire horizon dated using the AMS radiocarbon "wiggle matching" technique at 1040 ± 90 B.P. Keywords: Carbon accumulation, charcoal, dating, dendrochronology, fire

Alm, Department of Biology, University of Joensuu, P.O. Box 111, FIN-80100 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
Tolonen, Sähköposti: ei.tietoa@nn.oo
Vasander, Sähköposti: ei.tietoa@nn.oo

Bo H. Svensson, Ingvar Sundh. Factors affecting methane production in peat soils.

Avainsanat: Carbon flow; methanogenic bacteria; methanotrophic bacteria; mire ecology

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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

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
Bartlett, Sähköposti: ei.tietoa@nn.oo
Roulet, Sähköposti: ei.tietoa@nn.oo

Hans Persson. Factors affecting fine root dynamics of trees.

Avainsanat: fertilization; Carbon budget; fine root production; liming; minirhizotron; mycorrhiza; root tip; soil temperature; soil water

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Perhaps the most important function of the fine root system of forest trees is in the uptake of water and mineral nutrients. To perform this function adequately, the root system must be extensive and active enough to meet the needs of the canopy. Literature indicates that fine root production is substantial and that the seasonal pattern of fine root production is different from that of foliage production. Carbon incorporation into the soil in the form of dead roots is an important pathway in the total carbon flow through forest ecosystems. Root growth is sensitive to various climatic factors which are often imposed or strengthened by human activities. Factors that lead to growth suspension may or may not be the same as those that result in root shedding or senescence. The use of minirhizo-trons to study fine root dynamics means that ecologists are no longer justified in claiming that below-ground production is impossible to quantify in forest ecosystems. Keywords: Carbon budget, fine root production, liming, fertilization, minirhizotron, mycorrhiza, root tip, soil temperature, soil water

Persson, Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Box 7072, S-750 07 Uppsala, Sweden 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
Urban, Sähköposti: ei.tietoa@nn.oo

R. S. Clymo. Models of peat growth.

Avainsanat: peatland; Carbon balance; modelling; peat growth

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Models reflect reality but also simplify it. The modeller must choose where the balance lies between simplicity plus understanding and complexity plus realism. (1) Two pictorial and descriptive models of the surface of a peat-forming bog are given, and a third shows why the true rate of peat accumulation must diminish over time. (2) A simple quantitative model of the surface layers is described and leads to the conclusion that the surface layer is in a steady state, fixing carbon, losing some by decay, and passing some on to the underlying peat proper. A similar model for the underlying peat shows that if decay is at a rate that is a constant proportion of what remains then there is an upper asymptotic limit to the depth of peat. But if the rate of decay decreases, because the remaining material is more refractory, then peat accumulation continues indefinitely though at an ever-decreasing rate. (3) A simulation model allowing greater realism but diminished understanding is outlined. (4) Models should be aids, not objects in their own right. Keywords: Carbon balance, modelling, peat growth, peatland

Clymo, School of Biological Sciences, Queen Mary and Westfield College, London El 4NS, UK Sähköposti: ei.tietoa@nn.oo

Kimmo Tolonen. Mitä suoarkistot voivat meille tulevaisuudessa kertoa?

English title: What would be the significance of peat archives in the future?

Avainsanat: Carbon balance; dating; fire; DDT; global warming; heavy metals; PAHs

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An attempt is made to predict the progress of mire palaeoecological research in the near future. The prognosis is made in the light of recent advances in the field. Examples of some multi-faceted topics are given. They include ancient climatic changes for understanding the present changes, the greenhouse-effect, problems and new innovations in dating, organic pollutants such as PAHs and DDT, heavy metals and related air pollutants, man-made radionuclides, initiation of peatlands, peat growth, and fire history. Keywords: Carbon balance, dating, fire, DDT, global warming, heavy metals, PAHs

Tolonen, Department of Biology, University of Joensuu, P.O. Box 111, SF-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo

Jouko Silvola. Ojituksen ja lannoituksen vaikutus turpeen hiilen vapautumiseen ja ravinteiden mineralisoitumiseen.

English title: Effect of drainage and fertilization on carbon output and nutrient mineralization of peat.

Avainsanat: fertilization; Drainage; Carbon balance; nutrient mineralization; peat decomposition

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Carbon dioxide production increased to 2-3 fold from the peat of an oligotrophic sedge pine mire (VSR) after draining had lowered the water table to a depth c, 0.5 m. At two other sites, a mesotrophic sedge pine mire (RhSR) and a spruce swamp (MK), both the fall in the groundwater table and the increase in C02 production were smaller. At the VSR site, the fast-dissolving PK fertilizer and urea each caused a rapid increase while the slow-dissolving PK fertilizer a slow increase in soil respiration. The greatest, steady increase was achieved by treatment with wood ash. At RhSR and MK sites, the use of fertilizers generally led to a decline in soil respiration for 1-2 years, after which the initial level was normally regained. According to a simulation of the C02 production after drainage, the annual decomposition of peat was calculated to be c. 1 000 g (organic matter) m-2 in the VSR site. On the basis of this decomposition rate, the annual amount of nitrogen mineralizated was estimated to be c. 100 kg ha-1 and that of phosphorus c. 5 kg ha-1. Peat contains only a small amount of potassium, and the decomposition of old peat layers increases the amount of soluble potassium in peat very little. Keywords: Carbon balance, drainage, fertilization, nutrient mineralization, peat decomposition

Silvola, Department of Biology, University of Joensuu, P.O. Box 111, SF-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo

Minna Väliranta, Sanna Piilo, Hui Zhang. Viimeisten vuosisatojen lämpimien ja kylmien ilmastovaiheiden vaikutus ikiroutasoiden hiilidynamiikkaan ja hydrologisiin muutoksiin.

English title: Response of permafrost peatland hydrology and carbon dynamics to warm and cold climate phases during the last centuries.

Original keywords: hiilen kertyminen; ilmastonmuutos; hydrologiset muutokset; ikiroutasuot; kasvimakrofossiilit; kuoriamebat

English keywords: climate change; Carbon accumulation; hydrological changes; permafrost peatlands; plant macrofossils; testate amoeba

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Väliranta, Environmental Change Research Unit (ECRU), Ekosysteemit ja ympäristö tutkimusohjelma; Helsinki Institute of Sustainability Science (HELSUS) Sähköposti: minna.valiranta@helsinki.fi
Piilo, Environmental Change Research Unit (ECRU), Ekosysteemit ja ympäristö tutkimusohjelma; Helsinki Institute of Sustainability Science (HELSUS) Sähköposti: sanna.piilo@helsinki.fi
Zhang, Institute for Atmospheric and Earth System Research (INAR), Fysiikan laitos, Helsingin yliopisto Sähköposti: hui.zhang@helsinki.fi

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