ISSN 1239-6095
© Boreal Environment Research 2007

Contents of Volume 12 Number 2

Laine, J. 2007: Preface. Boreal Env. Res. 12: 81–83.
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Alm, J., Shurpali, N. J., Tuittila, E.-S., Laurila, T., Maljanen, M., Saarnio, S. & Minkkinen, K. 2007: Methods for determining emission factors for the use of peat and peatlands — flux measurements and modelling. Boreal Env. Res. 12: 85–100.
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Saarnio, S., Morero, M., Shurpali, N. J., Tuittila, E.-S., Mäkilä, M. & Alm, J. 2007: Annual CO2 and CH4 fluxes of pristine boreal mires as a background for the lifecycle analyses of peat energy. Boreal Env. Res. 12: 101–113.
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Minkkinen, K., Laine, J., Shurpali, N. J., Mäkiranta, P., Alm, J. & Penttilä, T. 2007: Heterotrophic soil respiration in forestry-drained peatlands. Boreal Env. Res. 12: 115–126.
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Minkkinen, K., Penttilä, T. & Laine, J. 2007: Tree stand volume as a scalar for methane fluxes in forestry-drained peatlands in Finland. Boreal Env. Res. 12: 127–132.
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Maljanen, M., Hytönen, J., Mäkiranta, P., Alm, J., Minkkinen, K., Laine, J. & Martikainen, P. J. 2007: Greenhouse gas emissions from cultivated and abandoned organic croplands in Finland. Boreal Env. Res. 12: 133–140.
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Lohila, A., Laurila, T., Aro, L., Aurela, M., Tuovinen, J.-P., Laine, J., Kolari, P. & Minkkinen, K. 2007: Carbon dioxide exchange above a 30-year-old Scots pine plantation established on organic-soil cropland. Boreal Env. Res. 12: 141–157.
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Mäkiranta, P., Hytönen, J., Aro, L., Maljanen, M., Pihlatie, M., Potila, H., Shurpali, N. J., Laine, J., Lohila, A., Martikainen, P. J. & Minkkinen, K. 2007: Soil greenhouse gas emissions from afforested organic soil croplands and cutaway peatlands. Boreal Env. Res. 12: 159–175.
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Yli-Petäys, M., Laine, J., Vasander, H. & Tuittila, E.-S. 2007: Carbon gas exchange of a re-vegetated cut-away peatland five decades after abandonment. Boreal Env. Res. 12: 177–190.
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Alm, J., Shurpali, N. J., Minkkinen, K., Aro, L., Hytönen, J., Laurila, T., Lohila, A., Maljanen, M., Martikainen, P. J., Mäkiranta, P., Penttilä, T., Saarnio, S., Silvan, N., Tuittila, E.-S. & Laine, J. 2007: Emission factors and their uncertainty for the exchange of CO2, CH4 and N2O in Finnish managed peatlands. Boreal Env. Res. 12: 191–209.
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Kirkinen, J., Minkkinen, K., Penttilä, T., Kojola, S., Sievänen, R., Alm, J., Saarnio, S., Silvan, N., Laine, J. & Savolainen, I. 2007: Greenhouse impact due to different peat fuel utilisation chains in Finland — a life-cycle approach. Boreal Env. Res. 12: 211–223.
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Lapveteläinen, T., Regina, K. & Perälä, P. 2007: Peat-based emissions in Finland's national greenhouse gas inventory. Boreal Env. Res. 12: 225–236.
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Alm, J., Shurpali, N. J., Tuittila, E.-S., Laurila, T., Maljanen, M., Saarnio, S. & Minkkinen, K. 2007: Methods for determining emission factors for the use of peat and peatlands — flux measurements and modelling. Boreal Env. Res. 12: 85–100.

The purpose of this paper is to introduce the gas exchange measurement and flux calculation methods commonly used in the projects of the programme "Greenhouse gas emissions from the use of peat and peatlands in Finland". The methods include measurements of instantaneous fluxes of CO2, CH4 and N2O made at the ecosystem–atmosphere boundary using closed chamber, and whole ecosystem fluxes of the gases using micrometeorological EC tower extending above the canopy, and the integration of seasonal and annual fluxes. In addition, tools developed for gap filling of missing weather records, and generating complete weather patterns for the key environmental controls of the gas fluxes are introduced. Derivation of emission factors from the collected gas fluxes, capable of reproducing the dynamic, climate dependent nature is outlined.
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Saarnio, S., Morero, M., Shurpali, N. J., Tuittila, E.-S., Mäkilä, M. & Alm, J. 2007: Annual CO2 and CH4 fluxes of pristine boreal mires as a background for the lifecycle analyses of peat energy. Boreal Env. Res. 12: 101–113.

This study was conducted to improve the estimates of C gas fluxes in boreal ombrotrophic and minerotrophic mires used in the lifecycle analysis of peat energy. We reviewed literature and collected field data from two new sites in southern Finland. In the literature, annual estimates of net CO2 exchange varied from –85 to +67 g C m–2 a–1 for ombrotrophic mires and from –101 to +98 g C m–2 a–1 for minerotrophic mires. Correspondingly, net CH4 flux estimates varied from less than –1 up to –16 g C m–2 a–1 and from less than –1 up to –42 g C m–2 a–1 for ombrotrophic and minerotrophic mires, respectively. Negative values indicate net efflux from the ecosystem. The modelling of C gas fluxes for the 30 simulated years clearly highlighted the need for long-term records of multiple environmental factors from the same sites, and the need for a number of improvements in the modelling of fluxes, as well as the environmental conditions driving C fluxes. The reduction of uncertainty in the background values of lifecycle analyses requires more detailed knowledge of the mire types used for peat harvesting and long-term field measurements combined with the developed process models and meteorological information. The use of C gas fluxes in pristine mires as a background for anthropogenic emissions is, however, only one option. Another option could be to consider anthropogenic emissions from the use of peat energy as such.
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Minkkinen, K., Laine, J., Shurpali, N. J., Mäkiranta, P., Alm, J. & Penttilä, T. 2007: Heterotrophic soil respiration in forestry-drained peatlands. Boreal Env. Res. 12: 115–126.

Heterotrophic soil respiration (CO2 efflux from the decomposition of peat and root litter) in three forestry-drained peatlands with different site types and with a large climatic gradient from the hemi-boreal (central Estonia) to south (southern Finland) and north boreal (northern Finland) conditions was studied. Instantaneous fluxes varied between 0 and 1.3 g CO2-C m–2 h–1, and annual fluxes between 248 and 515 g CO2-C m–2 a–1. Variation in the annual fluxes among site types was studied only in the south-boreal site where we found a clear increase from nutrient-poor to nutrient-rich site types. More than half of the within-site variation was temporal and explained by soil surface (–5 cm) temperature (T5). The response of soil respiration to T5 varied between the sites; the most northerly site had the highest response to T5 and the most southerly the lowest. This trend further resulted in increased annual fluxes towards north. This unexpected result is hypothesised to be related to differences in site factors like substrate quality, nutrient status and hydrology but also to temperature acclimation, i.e., adaptation of decomposer populations to different climates.
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Minkkinen, K., Penttilä, T. & Laine, J. 2007: Tree stand volume as a scalar for methane fluxes in forestry-drained peatlands in Finland. Boreal Env. Res. 12: 127–132.

Forestry drainage is a method used extensively to grow timber in peat soils in Finland. Following drainage, the developing tree stand influences methane (CH4) emissions by altering plant and microbial communities through water-level drawdown, competition for nutrients and shading. Therefore there should be a close correlation between tree stand volume and CH4 fluxes in drained peatlands. We used previously published material along with data collected in this research programme to assess the potential of tree stand volume as a tool for estimating CH4 fluxes for drained peatland forests, and to quantify this relationship under conditions prevailing in Finland. There was a clear negative exponential relationship between tree stand volumes and CH4 emissions. Sites with small stand volume emitted CH4 after drainage (up to 4 g CH4 m–2 a–1), while larger stands consumed it (up to 1 g CH4 m–2 a–1); the turning point from source to sink was about 140 m3 ha–1. Similar relationships were also found for undrained mires, although not as clearly as for the drained sites. Since drained peatland forests in Finland are generally rather young in drainage age and small in stand volumes, they are still estimated to emit CH4 to the atmosphere, although the rate has substantially decreased after drainage.
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Maljanen, M., Hytönen, J., Mäkiranta, P., Alm, J., Minkkinen, K., Laine, J. & Martikainen, P. J. 2007: Greenhouse gas emissions from cultivated and abandoned organic croplands in Finland. Boreal Env. Res. 12: 133–140.

Human activities have enhanced the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) from organic soils. Drained peat soils may turn into a source of CO2 and N2O, whereas CH4 emission may generally decrease after drainage. Agricultural use, including ploughing, fertilization and irrigation, further enhances the decomposition of peat, and CO2 and N2O emissions. Cultivated organic soils are therefore significant sources of CO2 and N2O. In this paper we report greenhouse gas emissions from cultivated organic soils, and from abandoned organic agricultural soils, i.e. from organic soils where cultivation practices have ceased. We found that CO2 and N2O emissions from abandoned organic cropland soils do not generally decrease with time after agricultural practices have ceased, whereas CH4 fluxes from the atmosphere into the soil may gradually increase after leaving cultivation.
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Lohila, A., Laurila, T., Aro, L., Aurela, M., Tuovinen, J.-P., Laine, J., Kolari, P. & Minkkinen, K. 2007: Carbon dioxide exchange above a 30-year-old Scots pine plantation established on organic-soil cropland. Boreal Env. Res. 12: 141–157.

In the boreal zone, large areas of natural mires have been drained and used for agriculture, resulting in net carbon dioxide (CO2) emissions and increased nitrous oxide emissions but decreased methane emissions. However, due to structural changes in agriculture, a substantial area of cropland on organic soil has been afforested. In order to estimate the carbon balance of afforested organic-soil cropland, we measured CO2 and water vapour (H2O) fluxes during year above a Scots pine plantation (Pinus sylvestris) in the middle-boreal zone, using the micrometeorological eddy covariance method. We observed CO2 uptake by the Scots pine stand from late April to mid-October with a daily average net uptake from May to the beginning of October. However, there were also periods of daily net efflux. High ecosystem respiration rates continued throughout the winter (mean winter respiration 0.036 mg CO2 m–2 s–1). As an annual average, the 30-year-old pine stand was a small source of CO2 (+50 g m–2 a–1) to the atmosphere, showing that the CO2 sequestration into the ecosystem was able to compensate for most of the carbon that was released by heterotrophic respiration from the drained soil.
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Mäkiranta, P., Hytönen, J., Aro, L., Maljanen, M., Pihlatie, M., Potila, H., Shurpali, N. J., Laine, J., Lohila, A., Martikainen, P. J. & Minkkinen, K. 2007: Soil greenhouse gas emissions from afforested organic soil croplands and cutaway peatlands. Boreal Env. Res. 12: 159–175.

The effects of land-use and land-use change on soil greenhouse gas (GHG) fluxes are of concern due to Kyoto Protocol requirements. To quantify the soil GHG-fluxes of afforested organic soils in Finland, chamber measurements of soil CO2, CH4 and N2O fluxes were made during the years 2002 to 2005 on twelve organic soil cropland and six cutaway peatland sites afforested 9 to 35 years ago. The annual soil CO2 effluxes were statistically modelled using soil temperature as the driving variable and the annual CH4 and N2O fluxes were estimated using the average fluxes during the measurement period. Soil CO2 effluxes on afforested organic soil croplands varied from 207 to 539 g CO2-C m–2 a–1 and on cutaway peatlands from 276 to 479 g CO2-C m–2 a–1. Both the afforested organic soil cropland and cutaway peatland sites acted mainly as small sinks for CH4; the annual flux ranged from –0.32 to 0.61 g CH4-C m–2. Afforested organic croplands emitted more N2O (from 0.1 to over 3.0 g N2O-N m–2 a–1) than cutaway peatland sites (from 0.01 to 0.48 g N2O-N m–2 a–1). Due to the decrease in soil CO2 efflux, and no change in CH4 and N2O fluxes, afforestation of organic croplands appears to decrease the greenhouse impact of these lands.
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Yli-Petäys, M., Laine, J., Vasander, H. & Tuittila, E.-S. 2007: Carbon gas exchange of a re-vegetated cut-away peatland five decades after abandonment. Boreal Env. Res. 12: 177–190.

Only little is known about the long-term carbon dynamics related to peatland restoration. We studied CO2 and CH4 dynamics of spontaneously regenerated peat trenches five decades after peat harvesting had ceased. We used non-linear regression models and interpolation for simulating gas exchange of four regenerating plant communities during two growing seasons and one winter. The studied communities all acted as seasonal (June–September) sinks of CO2 between 14 and 118 g C m–2, while the emissions of CH4 ranged from –4.9 to –28.8 g C m–2. When the winter time losses of carbon and the estimated leaching were subtracted, the balance was very low or negative: between –67 and 31 g C m–2. The low or even negative annual carbon balance in all communities may suggest a decrease in carbon sink strength in the advanced regeneration after the previously observed strong sink in the first regeneration stages caused by mass colonization by Eriophorum.
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Alm, J., Shurpali, N. J., Minkkinen, K., Aro, L., Hytönen, J., Laurila, T., Lohila, A., Maljanen, M., Martikainen, P. J., Mäkiranta, P., Penttilä, T., Saarnio, S., Silvan, N., Tuittila, E.-S. & Laine, J. 2007: Emission factors and their uncertainty for the exchange of CO2, CH4 and N2O in Finnish managed peatlands. Boreal Env. Res. 12: 191–209.

This paper summarises the results of several research groups participating in the research programme "Greenhouse Impacts of the use of Peat and Peatlands in Finland", and presents emission factors for peat–atmosphere fluxes of CO2, CH4, and N2O, filling gaps in knowledge concerning the afforestation of organic croplands and cutaways, and improves the emission assessment of peatlands drained for forestry. Forest drainage may result in net binding of soil carbon or net release, depending on site characteristics and the tree stand. Use of peatlands for agriculture (48–4821 g CO2-eq. m–2 a–1), even after the cultivation has ceased, or for milled peat harvesting (1948–2478 g CO2-eq. m–2 a–1) can cause the highest overall emissions. Extremely high CO2 emissions are possible from peat harvesting areas during wet and warm summers. Afforestation of those peatlands abandoned from cultivation or peat harvesting can reduce the warming impact at least during the first tree generation. Heterotrophic soil respiration may have a systematic south–north difference in temperature response. More data must be collected before the information on peatland forest soil CO2 emissions can be adapted for different climatic regions in Finland. A test of the model DNDC against measured data showed that DNDC has to be developed further before it can be used in estimating N2O emissions from boreal peatlands.
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Kirkinen, J., Minkkinen, K., Penttilä, T., Kojola, S., Sievänen, R., Alm, J., Saarnio, S., Silvan, N., Laine, J. & Savolainen, I. 2007: Greenhouse impact due to different peat fuel utilisation chains in Finland — a life-cycle approach. Boreal Env. Res. 12: 211–223.

Greenhouse impacts of different peat fuel utilisation chains were studied. A life cycle approach was used in order to cover all important emissions and sinks due to activities linked to the peat fuel production and utilisation. Radiative forcing was used to describe the greenhouse impact, and the results are given per one petajoule of energy produced. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions and sinks were considered. Investigated peat production reserves were pristine peatland (fen), forestry-drained peatland, and cultivated (cropland) peatland. The considered phases of the peat utilisation chain included peat fuel production, storage, transport, combustion and the after-treatment of the cut-away peatland. After-treatment alternatives were afforestation and restoration. The greenhouse impact of a considered peat fuel chain was calculated by subtracting the emissions/sinks of a production reserve in a state of non-utilisation from the emissions/sinks of peat utilisation chain. According to the results, the most climate-friendly peat production chain is cultivated peatland–afforestation. Cultivated peatland has large greenhouse gas emissions and these emissions from the land area are ceased by the removal of the peat layer, when the area is utilised for peat fuel production. If forestry-drained peatland or pristine fen is used for peat fuel production, the greenhouse impacts of these chains are of the order of the greenhouse impact of the utilisation chain for coal. Improvement of peat production and combustion methods can be applied to decrease to some extent the greenhouse effect of peat energy.
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Lapveteläinen, T., Regina, K. & Perälä, P. 2007: Peat-based emissions in Finland's national greenhouse gas inventory. Boreal Env. Res. 12: 225–236.

Peat-based emissions are reported under three different reporting sectors in Finland's national greenhouse gas inventory: Agriculture, Land Use, Land-Use Change and Forestry (LULUCF) and Energy. Peat-based emissions comprise together around one third of the total reported net greenhouse gas emissions in Finland when also sinks and emissions from LULUCF sector are included. Most of the emissions come from the combustion of peat for energy but emissions from the agricultural use of peatlands and drained forest soils are also of importance. The IPCC (Intergovernmental Panel on Climate Change) provides the basic guidelines for the inventory calculations. However, the use of national methods and emission factors is encouraged. Introducing new country-specific methods or emission factors in the inventory calculations requires transparent documentation of the input parameters and the process how emission factors, parameters and models are derived. Here we describe the national system for estimating peat-based emissions for the greenhouse gas inventory, and the methods that are used in deriving the emission estimates, as well as possibilities to use new national emission factors for improving the estimates.
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