Suo - Mires and peat vol. 43 no. 4-5 | 1992

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

The micrometeorological eddy correlation technique was used to measure fluxes of methane and energy. Results from these measurements made in a Minnesota peatland are reviewed here. The field observations made in a pilot study (1990) demonstrated the utility of the eddy correlation technique for measuring surface fluxes of methane. Seasonal distribution of methane flux at the same site was obtained in a detailed study (May to October) in 1991. The evapotranspiration rates and other components of the surface energy budget were also quantified. The daily evapotranspiration during the measurement period (mid May to mid October) ranged from 0.9 to 6.0 mm day-1, with a seasonal average of 3.6mm day-1. Keywords: Eddy correlation technique, methane flux, peatlands

• Verma, Dept. of Agric. Meteorology, University of Nebraska, P.O. Box 830728, Lincoln, NE-68583-0728, U.S.A. Sähköposti: ei.tietoa@nn.oo
• Ullman, Sähköposti: ei.tietoa@nn.oo
• Shurpali, Sähköposti: ei.tietoa@nn.oo
• Clement, Sähköposti: ei.tietoa@nn.oo
• Kim, Sähköposti: ei.tietoa@nn.oo
• Billesbach, Sähköposti: ei.tietoa@nn.oo

This study considered the effects on carbon pools in a forested mire following whole-tree harvesting and two site preparation treatments; bedding and trenching. Whole-tree harvesting, which resulted in complete removal of the overstory biomass, and bedding exhibited the greatest loss of carbon from the site. Removal of the overstory biomass and increased decomposition of organic matter were the major causes of carbon loss. Measurement of the soil carbon pools in the tree planting zone did not provide an accurate assessment of the treatment effect. Renewal of carbon accumulation will depend on the productivity and composition of the regenerating plant community and on the rate of decomposition of organic matter. Keywords: Decomposition, organic matter, site preparation, whole-tree harvest

• Trettin, Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008 MS-6038, Oak Ridge, 77V 37831-6038 U.S.A Sähköposti: ei.tietoa@nn.oo
• Gale, Sähköposti: ei.tietoa@nn.oo
• Jurgensen, Sähköposti: ei.tietoa@nn.oo
• McLaughlin, Sähköposti: ei.tietoa@nn.oo

The rate of carbon accumulation (RCA) was studied stratigraphically in individual vertical cores representing 25 mires in Finland, Estonia and Maine, USA. Carbon 14-datings (325 in total) were used for dating long cores encompassing all or most of the Holocene. The apparent long-term RCA (g m-2 a-1) in Finnish raised bogs and fens ranged from 13 to 41 and from 8 to 25, respectively, and in Maine bogs from 20 to 26 and in a single fen 27. Between and within core variations were great. In Finnish mires the true RCA, as derived from Clymo's peat accumulation model for long cores, was usually about 2/3 of the apparent long-term RCA. A change from intensive decay in the surface layers to very slow decay in deeper peat layers was dated to between some 300-500 years ago. Key words: Climatic change, organic matter, stratigraphy

• Tolonen, Department of Biology, University of Joensuu, P.O. Box III, FIN-80I01, Finland Sähköposti: ei.tietoa@nn.oo
• Vasander, Sähköposti: ei.tietoa@nn.oo
• Damman, Sähköposti: ei.tietoa@nn.oo
• Clymo, Sähköposti: ei.tietoa@nn.oo

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

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

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

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

The hydrology and hydrochemistry of Lakkasuo (Orivesi, central Finland) was studied for a 12-month period (September 1991-August 1992). Results from four monitored catchments in Lakkasuo are presented. The catchments represent a bog and a fen, both in the natural state and as drained for forestry 30 years ago. In the relatively wet study period (runoff 414 mm for the undrained bog), the catchments released 8.0-16.6 g m-2 of organic carbon (mainly dissolved) into runoff waters. All the catchments retained total N and sulphate provided by deposition or groundwater very effectively (65-80% and 52-72%, respectively); undrained catchments retained also total P. The net output rates of all the elements except H+ were greater from the drained catchments compared with the undrained ones. The leaching rates of Mg and Ca from the drained catchments were great compared with the pool of these elements in the surface peat, whereas the K pool is more effectively retained and added to by deposition. Keywords: Bog, fen, hydrochemistry, hydrology

• Sallantaus, National Board of Waters and the Environment, Water and Environment District of Tampere, P.O. Box 297, FIN-30I0I Tampere, Finland Sähköposti: ei.tietoa@nn.oo

The carbon balance of undrained and drained parts of a herb-rich pine fen mire ecosystem were calculated. The drainage had been carried out twenty years earlier. Drainage resulted in an increase of 1.23 t C ha-1 a-1 within the ecosystem. The increase was due to increased stand production, which exceeded a loss of carbon from the peat (-0.32 t ha-1 a-1). Keywords: Peat, peatland forestry, phytomass, Russia

• Sakovets, Karelian Science Centre, Forest Institute, Pushkinskaja II, 185610 Petrozavodsk, Russia Sähköposti: ei.tietoa@nn.oo
• Germanova, Sähköposti: ei.tietoa@nn.oo

Below-ground biomass of dominating vascular plants on a mesotrophic fen and Sphagnum fuscum pine bog was estimated using 14C labelling techniques. Preliminary results show that up to 90% of living biomass of Carex rostrata growing on the fen may be located below ground. Fine roots form the majority of below-ground biomass. Keywords: Peatlands, production, root biomass

• Saarinen, Department of Botany, Laboratories of Ecology, P.O. Box 4, FIN-00014University of Helsinki, Finland Sähköposti: ei.tietoa@nn.oo
• Tolonen, Sähköposti: ei.tietoa@nn.oo
• Vasander, Sähköposti: ei.tietoa@nn.oo

The peatlands of Borneo have been classified into coastal, basin/valley and high peats. Their formation is related to past and present climatic conditions, land erosion, sediment transport and deposition, pedogenesis, fluctuations in sea level and coastal building/uplift processes. The age of tropical peat varies from around 800 years to in excess of 10 000 years. The natural vegetation of tropical peatlands is forest within which most of the tree families of lowland dipterocarp rain forest have been recorded although the canopy is lower and more open. Tropical peatlands perform important ecological, economic and environmental functions. Keywords: Deferrification, peatland, tropical podzols

• Rieley, Department of Life Science, University of Nottingham, University Park, Nottingham, NG7 2RD, UK Sähköposti: ei.tietoa@nn.oo
• Sieffermann, Sähköposti: ei.tietoa@nn.oo
• Page, Sähköposti: ei.tietoa@nn.oo

Methane fluxes were measured using a static chamber technique on a minerotrophic fen and an ombrotrophic peat bog site located on the Lak-kasuo mire complex in central Finland. Both sites consisted of a virgin area and an area drained in 1961 by ditching. The measurements in 1991 were made biweekly from spring thaw to winter freezing. During this period, the mean CH4 emission from the virgin minerotrophic site and virgin ombrotrophic site was 98 mg m-2 d-1 and 40 mg m-2 d-1 , respectively. The mean emission of CH4 from the drained ombrotrophic site was 18 mg m-2 d-1. The drained minerotrophic site consumed methane during most of the measuring period, the average uptake was 0.13 mg m-2 d-1. Draining had lowered the average water table by 4 cm at the ombrotrophic site and by 20 cm at minerotrophic site. The possible reasons for the different development of the water table and methane fluxes at ombrotrophic and minerotrophic sites after draining are discussed. Keywords: Drainage, methane flux, methane oxidation, nutrient status, peat soil

• Martikainen, Department of Environmental Microbiology, National Public Health Institute, P.O. Box 95, FIN-70701 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo
• Nykänen, Sähköposti: ei.tietoa@nn.oo
• Crill, Sähköposti: ei.tietoa@nn.oo
• Silvola, Sähköposti: ei.tietoa@nn.oo

Methane production and consumption in drained minerotrophic and ombrotrophic peat was investigated using a combination of field measurement and laboratory incubations. In the field, methane fluxes were measured at intervals over a seven (minerotrophic) and ten (ombrotrophic) month period together with measurements of methane concentrations and temperature at various depths. In the laboratory, aerobic incubations of drained peat samples from various depths were conducted over a range of temperatures to determine rates of potential methane oxidation. The maximum potential methane oxidation rate occurred at a depth close to that of the water table. The oxidation rate was much higher in the ombrotrophic peat than in the minerotrophic peat. However, field measured methane fluxes were lower in the minerotrophic peat. This is attributed to a relatively low water table. Methane oxidation increased over the temperature range 2 to 30°C and decreased at temperatures >34°C. Methane production in the aerobic incubation experiment was measured by inhibition of methane oxidation with dimethyl ether. Production rates were only 1-7% of net oxidation rates. Thus, the measured net rates of methane absorption in aerobic incubations largely reflect gross oxidation rates. Keywords: Bog, fen, temperature, water level

• Lien, Department of Biotechnological Sciences, Agricultural University of Norway, P.O. Box 5040, N-I432 Aas, Norway Sähköposti: ei.tietoa@nn.oo
• Martikainen, Sähköposti: ei.tietoa@nn.oo
• Nykänen, Sähköposti: ei.tietoa@nn.oo
• Bakken, Sähköposti: ei.tietoa@nn.oo

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

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

Activity during the first phase of this SUOSILMU subproject was mainly focused on the development of methods for the fractionation of peat into its organic components and for the determination of microbial bio-mass. It is now possible to characterise peat using some fifty organic compounds. Using these methods, the effects of drainage intensity and fertilization on the organic character of the peat have been investigated. From the preliminary results, it appears that these methods can be used to determine more exactly the effects of such amelioration practices on the decomposition of peat. During the next phase of the project (1993— 1995), the production and decomposition rates of different organic compounds will be determined in long-term incubation experiments. Keywords: Decomposition, microbiological analysis, organic compounds, peatland

• Karsisto, The Finnish Forest Research Institute, Department of Forest Ecology, P.O. Box 18, FIN-0I30I Vantaa, Finland 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

Total fine root biomass was 397 g/m2 at an afforested and fertilized tall sedge fen (VSN), and 529 g/m2 at a tall sedge pine fen (VSR). The studied sites were located on the Lakkasuo mire complex in central Finland. The greater biomass on the VSR site could be a result of its lower nutrient status compared to that of the fertilized VSN site. Total root production during May-September 1991 was 178 g/m2 at the VSN site and 242 g/m2 at the VSR site when all significant increments in the living and dead root biomasses were summed up. Almost half of the fine root biomass was renewed during the summer. Keywords: Biomass, drainage, ground vegetation, necromass, Pinus sylvestris, production

• Finér, Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, FIN-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
• Laine, Sähköposti: ei.tietoa@nn.oo
• Halko, Sähköposti: ei.tietoa@nn.oo

Some preliminary results of a technique used to compare primary production and peat accumulation data mainly from published sources and the results of a peat accumulation simulation model are presented. Emphasis is on differences among micro-sites (hummock, lawn, hollow and pool) and among various Sphagnum species (S.fuscum, S. magellanicum, S. cuspidatum and S. balticum) associated with raised bogs. The primary production of lawns and pools were significantly greater than those of hummocks and hollows. Sphagnum balticum had the highest primary production (mean = 339 g m-2 a-1). Over 90% of the primary production of Sphagnum fuscum is accumulated while for the other Sphagnum species, the value is <50%. The data are used in a simulation model to show the influence on primary production of a doubling of rainfall over a 50-year period. Keywords: Meta-analysis, peatland, primary production, Sphagnum

• Dierendock, Hugo de Vries Laboratory, University of Amsterdam, Kruislaan 318, J 098 SM Amsterdam, The Netherlands Sähköposti: ei.tietoa@nn.oo

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

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

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

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 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

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

Difficulties in separating fine roots from a purely organic matrix preclude the use of traditional root-harvesting techniques when studying the below-ground production of the field layer species in mires. Also methods based on different types of installations, such as ingrowth chambers or rhizotrons, cause a significant disturbance of the root environment. Indirect techniques using isotope-labelling avoid many of these problems and are the most suited for studying below-ground processes in peatlands. A technique based on translocation of 14C to the peat through the fine roots is demonstrated to evaluate the vascular plant biomass distribution in hummocks of a subarctic and a boreonemoral peat bog respectively. The technique fails to distinguish between structural and labile carbon and overestimates therefore the fine root biomass, but is useful for comparative purposes. It is shown that different mire plants have species-specific below-ground distributions, and that a proportionately greater share of carbon is allocated to fine roots in subarctic conditions. Keywords: Andromeda, Calluna, Empetrum, Eriophorum,root biomass, Rubus,translocation

• Wallén, Department of Plant Ecology, Lund University, Östra Vallgatan 14, S-223 61 Lund, Sweden Sähköposti: ei.tietoa@nn.oo

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

We determined the rate elements are sequestered in hummock peat of an ombrotrophic bog. The peat below 65 cm was radiocarbon dated and the upper 65 cm was dated using the acid insoluble ash (AIA) content and Polytrichum strictum growth increments. Peat produced during the last 9 yrs contains roughly all the N, P, Ca, and Mg, and about twice the K, deposited during this period. However, these nutrients are depleted from older peat at rates that depends on mineralization and adsorption properties of the ions. Changes in inorganic chemistry occur mostly while peat is in the acrotelm. Therefore, only peat in the catotelm will show the true accumulation rate of elements. In peat below 65 cm, the annual accumulation rate, as a percent of the present annual input, is: N-38, K-2.5, P-18, Na-1.5, Ca-3, Mg-51 and S-3.5%. Dust fall increased 4-fold about 500 yrs ago and has remained at this level. Therefore, the annual accumulation of elements in peat below 65 cm, or older than 522 yrs, presumably underestimates present accumulation in the catotelm of soil-derived elements, especially Ca and P, and elements that have increased due to pollution such as N and S. This increased dust fall probably changed the floristic composition of the vegetation as well as production and decay. Keywords: Accumulation, dating, element retention, input changes, nutrient dynamics

• Damman, Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Road, Storrs, CT 06269-3042, USA Sähköposti: ei.tietoa@nn.oo
• Tolonen, Sähköposti: ei.tietoa@nn.oo
• Sallantaus, Sähköposti: ei.tietoa@nn.oo

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

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
• Janssens, Sähköposti: ei.tietoa@nn.oo