| 1. |
- Björk, Robert G., 1974, et al.
(författare)
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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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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 73:3, s. 550-562
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Ernfors, Maria, 1973, et al.
(författare)
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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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Ingår i: SCIENCE OF THE TOTAL ENVIRONMENT. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 408:20, s. 4580-4590
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Ernfors, Maria, 1973, et al.
(författare)
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Greenhouse gas dynamics of a well-drained afforested agricultural peatland
- 2020
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Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 25, s. 65-77
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Tidskriftsartikel (refereegranskat)abstract
- About a quarter of the global anthropogenic greenhouse gas emissions are attributable to agriculture, forestry and other land use. Few studies of afforested drained peatlands have measured exchanges of all three major greenhouse gases (GHG) at a given site, leading to uncertainty in estimated GHG budgets. Thus, we measured forest floor exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at a well-drained afforested peatland in southern Sweden. The CO2 emissions (76 000 kg ha–1 a–1; SE 6 000) were large compared with previous measurements at similar sites, which may have been partly due to a measurement technique that did not underestimate the flux. A net CH4 uptake of 4.4 kg ha–1 a–1 (SE 0.41) and a net N2O emission of 2.7 kg ha–1 a–1 (SE 0.23) were found, which agreed well with published models relating fluxes to stand biomass (CH4 models) or soil C:N ratio (N2O models).
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| 4. |
- Ernfors, Maria, 1973
(författare)
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Greenhouse gas fluxes between drained forested peatlands and the atmosphere - influence of nutrient status and wood ash fertilization
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The management of peatlands for wood production involves drainage and, sometimes, fertilization with, for example, wood ash. The effects of these measures on greenhouse gas fluxes, in relation to the ... mernutrient status of the peat, were studied at three sites in southern Sweden. The carbon dioxide (CO2) fluxes from a well drained nutrient rich peatland, with an agricultural history, were found to be high (71 000 kg ha-1 a-1), in comparison to earlier studies of similar sites. There was also a net uptake of CH4 (-4.4 kg ha-1 a-1) and a net emission of N2O (2.7 kg ha-1 a-1). At two nutrient poor sites, one of which was well drained and one poorly drained, there were net CH4 emissions (5.1 and 8.5 kg ha-1 a-1, respectively; averaged over three years) and no fluxes of N2O. The CO2 flux values measured at the nutrient poor sites (9 500 and 13 000 kg ha-1 a-1, respectively; averaged over three years) were considered to be underestimates, due to the measurement technique used. The N2O fluxes from all three sites where gas fluxes were measured agreed well with predictions made on the basis of the C:N ratio of the peat. At a nutrient poor site, ash fertilization did not result in any changes in greenhouse gas emissions over a period of five years after the treatment. However, signs of increased tree growth, and thereby increased CO2 uptake, were detectable in the fifth year. At a nutrient rich site, which was studied over a period of two years after ash fertilization, CO2 and N2O emissions from the treated plots decreased, but no changes in tree stand growth were detected. The decrease in N2O emissions was attributed to an increase in pH in the ash fertilized plots, which affected the N2O winter fluxes. The preliminary conclusion was that wood ash fertilization has a positive influence on the greenhouse gas balance of drained peatlands. Analyses of soil samples from three drained peatlands – two treated recently with wood ash and one that was treated 25 years earlier – supported this conclusion by showing no major changes in microbial processes, community structure or biomass, apart from decreases in net nitrogen mineralization and microbial biomass (as indicated by PLFA) at the nutrient poor sites. The studies upon which this thesis is based were mainly short-term; for definitive conclusions to be drawn, gas fluxes must be studied over the long-term.
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| 5. |
- Ernfors, Maria, 1973, et al.
(författare)
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Increased nitrous oxide emissions from a drained organic
- 2011
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Ingår i: Plant and soil.
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine how roots and their ectomycorrhizal symbionts affect the fluxes of nitrous oxide (N2O) from nutrient-rich drained organic forest soils. Specifically, the relative impacts of roots and mycorrhizal mycelia on N2O fluxes were investigated using two different trenching treatments, excluding (a) roots or (b) roots and mycorrhizal mycelia, from the soil. N2O fluxes were measured at the soil surface, for 1 year before and 2.5 years after trenching, within the two trenching treatments and on untreated controls. While the exclusion of roots alone did not affect N2O emissions, the simultaneous exclusion of roots and mycorrhizal mycelia doubled N2O emissions, compared to the control plots. Two probable explanations for the increased fluxes were identified: (1) a decreased uptake of nitrogen (N) from the soil, through the mycorrhizal fungi, which increased N availability for the N2O-producing microorganisms, and (2) a decreased uptake of water from the soil, through the mycorrhiza, which increased the soil water content and thus the N2O emissions from denitrification. If the trenching reduced any potential stimulation of N cycling, through rhizodeposition, this mechanism did not outweigh the effects of a discontinued mycorrhizal N and/or water uptake on N2O fluxes. The results of the study emphasise the importance of ectomycorrhiza in regulating N2O emissions from forested organic soils.
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| 6. |
- Ernfors, Maria, 1973, et al.
(författare)
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Increased nitrous oxide emissions from a drained organic forest soil after exclusion of ectomycorrhizal mycelia
- 2011
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Ingår i: Plant and Soil. - 0032-079X. ; 343:1-2, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine how roots and their ectomycorrhizal symbionts affect the fluxes of nitrous oxide (N2O) from nutrient-rich drained organic forest soils. Specifically, the relative impacts of roots and mycorrhizal mycelia on N2O fluxes were investigated using two different trenching treatments, excluding (a) roots or (b) roots and mycorrhizal mycelia, from the soil. N2O fluxes were measured at the soil surface, for 1 year before and 2.5 years after trenching, within the two trenching treatments and on untreated controls. While the exclusion of roots alone did not affect N2O emissions, the simultaneous exclusion of roots and mycorrhizal mycelia doubled N2O emissions, compared to the control plots. Two probable explanations for the increased fluxes were identified: (1) a decreased uptake of nitrogen (N) from the soil, through the mycorrhizal fungi, which increased N availability for the N2O-producing microorganisms, and (2) a decreased uptake of water from the soil, through the mycorrhiza, which increased the soil water content and thus the N2O emissions from denitrification. If the trenching reduced any potential stimulation of N cycling, through rhizodeposition, this mechanism did not outweigh the effects of a discontinued mycorrhizal N and/or water uptake on N2O fluxes. The results of the study emphasise the importance of ectomycorrhiza in regulating N2O emissions from forested organic soils.
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| 7. |
- Ernfors, Maria, 1973, et al.
(författare)
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Nitrous oxide emissions from drained organic forest soils - an up-scaling based on C : N ratios
- 2007
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 84:2, s. 219-231
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Tidskriftsartikel (refereegranskat)abstract
- Total emissions of N2O from drained organic forest soils in Sweden were estimated using an equation linking the C:N ratio of the soil to N2O emissions. Information on soil C:N ratios was derived from a national database. It was estimated that the emissions from Histosols amount to 2,820 tonnes N2O a(-1). This is almost five times the value calculated for the same soils using the method suggested by the Intergovernmental Panel on Climate Change: 580 tonnes N2O a(-1). The higher value in the present study can mainly be explained by improved accuracy of estimates of N2O emissions from nutrient-rich soils, including former agricultural soils. In Sweden, in addition to 0.94 Mha of drained Histosols, there are 0.55 Mha of other types of drained organic soils. The annual emissions from these soils were estimated to amount to 1,890 tonnes of N2O. The total emission value calculated for drained organic forest soils was thus 4,700 tonnes N2O a(-1), which, if added, would increase the current estimate of the Swedish anthropogenic N2O source strength by 18%. Of these emissions, 88% occur from sites with C:N ratios lower than 25. The exponential relationship between C:N ratio and N2O emissions, in combination with a scarcity of data, resulted in large confidence intervals around the estimates. However, by using the C:N ratio-based method, N2O emission estimates can be calculated from a variable that is readily available in databases. Also, the recent findings that there are exceptionally large emissions of N2O from the most nitrogen-rich drained organic forest soils are taken into account.
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| 8. |
- Klemedtsson, Leif, 1953, et al.
(författare)
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Bayesian calibration method used to elucidate carbon turnover in forest on drained organic soil
- 2008
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 89:1, s. 61-79
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Tidskriftsartikel (refereegranskat)abstract
- Depending on the balance between sink and source processes for C, drained organic forest soil ecosystems can be in balance or act as net sinks or sources of CO2 to the atmosphere. In order to study the effect of groundwater level and soil temperature on C-flux, the CoupModel was calibrated (climate data, groundwater levels, soil CO2 flux, net ecosystem fluxes of CO2-exchange, sensible heat flux and latent heat flux, forest production etc.) for a drained forest in Sweden. Bayesian calibration techniques were used to elucidate how different parameters and variables were interlinked in C-circulation. The calibrated model reproduced abiotic and biotic variables reasonably well except for root respiration, which was largely underestimated. Bayesian calibration reduced the uncertainties in the model and highlighted the fact that calibrations should be performed with a high number of parameters instead of specific parameter values.
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| 9. |
- Klemedtsson, Leif, 1953, et al.
(författare)
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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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Ingår i: European Journal of Soil Science. - : Wiley. - 1351-0754 .- 1365-2389. ; 61:5, s. 734-744
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Klemedtsson, Leif, 1953, et al.
(författare)
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Skogaryd – Integration of terrestrial and freshwater greenhouse gas sources and sinks
- 2010
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Ingår i: 1st COST meeting ‘Belowground carbon in Europeanforest’, Birmensdorf, Switzerland, 26–28 January 2010..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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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