| 1. |
- Berglund, Örjan, et al.
(author)
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A lysimeter study on the effect of temperature on CO2 emission from cultivated peat soils
- 2010
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In: Geoderma. - : Elsevier BV. - 0016-7061 .- 1872-6259. ; 154:3-4, s. 211-218
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Journal article (peer-reviewed)abstract
- A lysimeter method was evaluated for its suitability in gas emission studies by studying the effect of temperature on CO2 emissions (dark respiration) from cultivated peat soils. The study was carried out with organic soils from two locations in Sweden, a typical cultivated fen peat with low pH and high organic matter content (Örke) and a more uncommon fen peat with high pH and low organic matter content (Majnegården). A drilling method with minimal soil disturbance was used to collect 12 undisturbed soil lysimeters per site. CO2 emission was measured weekly from the vegetated lysimeters and the results were compared with data from incubation experiments. The CO2 emissions measured in the lysimeter experiment were in the same range as those in other studies and showed a similar increase with temperature as in the incubation experiment. With climatic and drainage conditions being similar in the lysimeter experiment, differences in daytime CO2 emission rates between soils (483 mg ± 6.9 CO2 m− 2 h− 1 from the Örke soil and 360 ± 7.5 mg CO2 m− 2 h− 1 from the Majnegården soil) were presumably due to soil quality differences. Q10 values of 2.1 and 3.0 were determined in the lysimeter experiment and of 1.9 to 4.5 in the incubation experiment for Örke and Majnegården respectively. CO2 emission data fitted well to a semi-empirical equation relating CO2 emissions to air temperature. The lysimeter method proved to be well suited for CO2 emission studies.
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| 2. |
- Björk, Robert G., 1974, et al.
(author)
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Climate-related soil changes in tundra ecosystems at Latnjajaure, northern Sweden – an ITEX-IPY project
- 2010
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In: International Polar Year Oslo Science Conference.
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Conference paper (peer-reviewed)abstract
- During the 90'ies, the International Tundra Experiment (ITEX) was established as a leading project in arctic and alpine ecology, and has become a model for many later network establishments. The present study capitalizes on the early efforts of ITEX and aims at assessing ecosystem changes in the alpine areas of northern Sweden above timberline, i.e. the tundra, in relation to global change. By using the "old" ITEX plots established during the early years of the program we have measured ecosystem respiration (ER), the Normalized Difference Vegetation Index, and nitrogen (N) mineralization over the growing season. In addition, have soil samples been taken to quantify changes in the carbon (C) and N pool, including 13C and 15N. After 12 to 15 years of open top chamber (OTC) treatment no statistical effect was found on the soil temperature (10 cm soil depth), although the was an overall increase in all OTC by +0.2°C. However, the soil moisture decreased significantly by 3-14%, depending on plant community, in the OTCs compared to ambient conditions. Preliminary, there was a 20-37% non-significant higher mean ER in the OTC compared to the ambient plots over the growing season. Furthermore, the OTC treatment did not affect the growing season mineralization of inorganic N, or total C and N content of the soil. The stable isotope data showed both enrichment and depletion as a consequence of the OTC treatment, but no general pattern was discerned. Thus, this non-significant higher ER is most likely of plant origin than soil, as the plant standing biomass has increased in the OTCs. This study does not support the current consensus that tundra soils will alter their C and N dynamics in response to climate change.
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| 3. |
- Björk, Robert G., 1974, et al.
(author)
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Contrasting effects of wood ash application on microbial community structure, biomass and processes in drained forested peatlands
- 2010
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In: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 73:3, s. 550-562
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Journal article (peer-reviewed)abstract
- The effects of wood ash application on soil microbial processes were investigated in three drained forested peatlands, which differed in nutrient status and time since application. Measured variables included concentrations of soil elements and phospholipid fatty acids (PLFAs), net nitrogen mineralisation, nitrification and denitrification enzyme activity, potential methane oxidation, methane production and microbial respiration kinetics. Wood ash application had a considerable influence on soil element concentrations. This mirrored a decrease in the majority of the microbial biomarkers by more than one-third in the two oligotrophic peatlands, although microbial community composition was not altered. The decreases in PLFAs coincided with reduced net ammonification and net nitrogen mineralisation. Other measured variables did not change systematically as a result of wood ash application. No significant changes in microbial biomass or processes were found in the mesotrophic peatland, possibly because too little time (1 year) had elapsed since the wood ash application. This study suggests that oligotrophic peatlands can be substantially affected by wood ash for a period of at least four years after application. However, within 25 years of the wood ash application, the microbial biomass seemed to have recovered or adapted to enhanced element concentrations in the soil.
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| 4. |
- Björk, Robert G., 1974, et al.
(author)
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Root biomass distribution and morphology in Norway spruce forests on drained organic soils: root system variation in d13C and d15N
- 2010
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In: 1st COST meeting ‘Belowground carbon in Europeanforest’, Birmensdorf, Switzerland, 26–28 January 2010..
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Conference paper (other academic/artistic)abstract
- Little is known about the distribution and morphology of fine roots in organic soils. Organic soils are typical features of northern Europe, covering over 250 000 km2, and in the recent century, 1/3 of the pristine peatlands have been drained for forestry and large areas of peatlands used for agriculture have been afforested. The aim of the present study was to investigate how fine root distribution, mor-phology, and 13C/15N differed between two fertile drained and forested organic soils. The study was conducted in two Norway spruce stands at the Skogaryd Research Forest, in south-west Sweden. One of the sites was a mineral soil (“the mineral site”) with high organic content that had been under agricultural use since the 15th century, and was afforested in 1962. The other site was a peat soil of minerotrophic origin (“the peat site”) that was used for extensive grazing from the 1800s to the 1870s, used for crop production after the drainage in the 1870s and afforested in 1951. Root biomass and necromass were estimated using soil cores, to a depth of 40 cm. Washed roots were scanned and sorted into five diameter classes, and analysed for 13C and 15N. There was a distinct difference in fine root morphology between the two sites, with longer and thinner roots at the peat site. Despite this, no significant differences in total root biomass or biomass-to-necromass ratio between the sites were found. At the peat site, the fine roots were en-riched in 15N by 1-1.5‰ compared to the mineral site, and had consistently lower C/N within the root classes. The mineral site, which is the less fertile of the sites, produced shorter and thicker roots, and more extensive extramatrical mycelia. Thus, one possibility is that the trees at the mineral site invest more in their mycorrhizal symbiont instead of exploring the soil environment themselves.
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| 5. |
- Björkman, Mats P., 1978, et al.
(author)
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A comparison of annual and seasonal carbon dioxide effluxes between sub-Arctic Sweden and High-Arctic Svalbard
- 2010
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In: Polar Research. - : Norwegian Polar Institute. - 1751-8369. ; 29:1
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Journal article (peer-reviewed)abstract
- Recent climate change predictions suggest altered patterns of winter precipitation across the Arctic. It has been suggested that the presence, timing and amount of snow all affect microbial activity, thus influencing CO2 production in soil. In this study annual and seasonal emissions of CO2 were estimated in High-Arctic Adventdalen, Svalbard, and sub-Arctic Latnjajaure, Sweden, using a new trace gas-based method to track real time diffusion rates through the snow. Summer measurements from snow-free soils were made using a chamber-based method. Measurements were obtained at different snow regimes in order to evaluate the effect of snow depth on winter CO2 effluxes. Total annual emissions of CO2 from the sub-Arctic site (0.662–1.487 kg CO2 m-2 yr-1) were found to be more than double the emissions from the High-Arctic site (0.369–0.591 kg CO2 m-2 yr-1). There were no significant differences in winter effluxes between snow regimes or vegetation types, indicating that spatial variability in winter soil CO2 effluxes are not directly linked to snow cover thickness or soil temperatures. Total winter emissions (0.004–0.248 kg CO2 m-2) were found to be in the lower range of those previously described in the literature. Winter emissions varied in their contribution to total annual production between 1 and 18%. Artificial snow drifts shortened the snow-free period by two weeks and decreased annual CO2 emission by up to 20%. This study suggests that future shifts in vegetation zones may increase soil respiration from Arctic tundra regions.
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| 6. |
- Björkman, Mats P., 1978, et al.
(author)
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Winter carbon dioxide effluxes from Arctic ecosystems: An overview and comparison of methodologies
- 2010
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In: Global Biogeochemical Cycles. ; 24, s. GB3010-
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Journal article (peer-reviewed)abstract
- The winter CO2 efflux from subnivean environments is an important component of annual C budgets in arctic ecosystems and consequently makes prediction and estimations of winter processes as well as incorporations of these processes into existing models important. Several methods have been used for estimating winter CO2 effluxes, involving different assumptions about the snow pack, all aiming to quantify CO2 production. Here, four different methods are compared and discussed: (1) measurements with a chamber on the snow surface, Fsnow; (2) chamber measurements directly on the soil, Fsoil, after snow removal; (3) diffusion measurements, F2-point, within the snow pack; and (4) a trace gas technique, FSF6, with multiple gas sampling within the snow pack. According to measurements collected from shallow and deep snow cover in High-Arctic Svalbard and Sub-Arctic Sweden during the winter of 2007-2008, the four methods differ by up to two orders of magnitude in their estimates of total winter emissions. The highest mean winter CO2 effluxes, 7.7-216.8 mg CO2 m-2 h-1, were observed using Fsoil and lowest values, 0.8-12.6 mg CO2 m-2 h-1, using FSF6. The Fsnow and F2-point methods were both within the lower range, 2.1-15.1 mg CO2 m-2 h-1 and 6.8-11.2 mg CO2 m-2 h-1, respectively. These differences are considered to be a result of contrasting methods, but also because the assumptions within the methods are not the same when quantifying CO2 production and effluxes to the atmosphere. Since snow can act as a barrier to CO2, Fsoil is assumed to measure soil production, whereas FSF6, Fsnow and F2-point are considered better approaches for quantifying exchange processes between the soil, snow, and the atmosphere. This study indicates that estimates of winter CO2 emissions may vary more as a result of the method used than due to the actual variation in soil CO2 production or release. This is a major concern, especially when CO2 efflux data are used in climate models or in carbon budget calculations, thus highlighting the need for further development and validation of accurate and appropriate techniques.
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| 7. |
- Ernfors, Maria, 1973, et al.
(author)
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Effects of wood ash fertilization on forest floor greenhouse gas emissions and tree growth in nutrient poor drained peatland forests
- 2010
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In: SCIENCE OF THE TOTAL ENVIRONMENT. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 408:20, s. 4580-4590
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Journal article (peer-reviewed)abstract
- Wood ash (3.1, 3.3 or 6.6 tonnes dry weight ha(-1)) was used to fertilize two drained and forested peatland sites in southern Sweden. The sites were chosen to represent the Swedish peatlands that are most suitable for ash fertilization, with respect to stand growth response. The fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the forest floor, measured using opaque static chambers, were monitored at both sites during 2004 and 2005 and at one of the sites during the period 1 October 2007-1 October 2008. No significant (p>0.05) changes in forest floor greenhouse gas exchange were detected. The annual emissions of CO2 from the sites varied between 6.4 and 15.4 tonnes ha(-1), while the CH4 fluxes varied between 1.9 and 12.5 kg ha(-1). The emissions of N2O were negligible. Ash fertilization increased soil pH at a depth of 0-0.05 m by up to 0.9 units (p<0.01) at one site, 5 years after application, and by 0.4 units (p<0.05) at the other site, 4 years after application. Over the first 5 years after fertilization, the mean annual tree stand basal area increment was significantly larger (p<0.05) at the highest ash dose plots compared with control plots (0.64 m(2) ha(-1) year(-1) and 0.52 m(2) ha(-1) year(-1), respectively). The stand biomass, which was calculated using tree biomass functions, was not significantly affected by the ash treatment. The groundwater levels during the 2008 growing season were lower in the high ash dose plots than in the corresponding control plots (p<0.05), indicating increased evapotranspiration as a result of increased tree growth. The larger basal area increment and the lowered groundwater levels in the high ash dose plots suggest that fertilization promoted tree growth, while not affecting greenhouse gas emissions.
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| 8. |
- Klemedtsson, Leif, 1953, et al.
(author)
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Reduction of greenhouse gas emissions by wood ash application to a Picea abies (L.) Karst. forest on a drained organic soil
- 2010
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In: European Journal of Soil Science. - : Wiley. - 1351-0754 .- 1365-2389. ; 61:5, s. 734-744
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Journal article (peer-reviewed)abstract
- Wood ash additions of 3.3 and 6.6 t ha(-1) reduced greenhouse gas (GHG) emissions from a spruce forest (Picea abies) on a minerotrophic drained organic soil. Emissions of carbon dioxide (CO(2)), methane (CH(4)) and nitrous oxide (N(2)O) were measured using static dark chambers for two years following the ash treatment. The CO(2) emission from the soil was significantly reduced by 17-23% by both doses during 2006-2008. The mechanism behind the reduction could not be related to a direct inhibition of soil C mineralization by the ash. The emission of N(2)O was also significantly reduced by 44 and 46% during the first year, mainly due to reductions in the winter emissions. Similar reductions of 34 and 50% were found in the second year for the low and the high wood ash, respectively. Increased pH of the soil due to the ash additions may have caused the effect. The control and amended soils consumed ambient CH(4). The low wood ash dose increased the annual net CH(4) uptake rate by 9%, due to an increased winter uptake. No changes in tree growth could be detected over the short 2-year measurement period. The net effect of wood ash application was a reduction in the total GHG emissions during the first two years after the treatment.
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| 9. |
- Klemedtsson, Leif, 1953, et al.
(author)
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Skogaryd – Integration of terrestrial and freshwater greenhouse gas sources and sinks
- 2010
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In: 1st COST meeting ‘Belowground carbon in Europeanforest’, Birmensdorf, Switzerland, 26–28 January 2010..
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Conference paper (other academic/artistic)abstract
- Forests play an important role in the global carbon (C) cycle, and management as well as climate can cause major effects on the balance of C between the atmosphere and the plant/soil system. With re-gard to our commitments to the Kyoto and post-Kyoto actions on climate change, we need reliable predictions on how this balance is affected by management and climate. In 2006 the Skogaryd Research Forest was established in the southwest of Sweden (58°23’N, 12°09’E). The overall goal is to quantify net greenhouse gas (GHG) fluxes from drained spruce forest, by determining the individual fluxes and pools of C and nitrogen and elucidating their connection to site fertility, drainage status and abiotic parameters and then use the generated data in GHG models, for model validations and ultimately emissions predictions. During 2006-2009 the research has fo-cused on two sites, mineral and organic, dominated by Norway spruce (Picea abies). Both sites are drained fertile soils but with different land-use history that have affected their physical properties. Measurements includes: net ecosystem exchange of CO2, Shoot photosynthesis and respiration at different locations within the canopy, stem respiration, emissions of N2O and CH4 using manual cham-bers, soil respiration with automatic chambers including a trenching experiment where root-, mycelia-, and heterotrophic respiration are separated, fine root production using minirhizotrons, and mycelia production. The organic site also includes a wood ash experiment. From 2010 the research will be expanded to the whole watershed, from the mire system via streams, riparian zones, forests, to lakes and the subsequent exchange between the atmosphere and surface waters. Different terrestrial and limnic ecosystems will be linked holistically, using site specific tech-niques at different scales, from aircraft (km2) to chambers (m2) to create integrated models that can be used to quantify net GHG flux for management strategies.
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| 10. |
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