| 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. |
- Elmendorf, Sarah C., et al.
(författare)
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Global assessment of experimental climate warming on tundra vegetation : heterogeneity over space and time
- 2012
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 15:2, s. 164-175
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Forskningsöversikt (refereegranskat)abstract
- Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation and associated ecosystem consequences have the potential to be much greater than we have observed to date.
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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. |
- 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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| 5. |
- 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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| 6. |
- Meyer, Astrid, et al.
(författare)
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A fertile peatland forest does not constitute a major greenhouse gas sink
- 2013
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 10, s. 7739-7758
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Tidskriftsartikel (refereegranskat)abstract
- Afforestation has been proposed as a strategy to mitigate the often high greenhouse gas (GHG) emissions from agricultural soils with high organic matter content. However, the carbon dioxide (CO2) and nitrous oxide (N2O) fluxes after afforestation can be considerable, depending predominantly on site drainage and nutrient availability. Studies on the full GHG budget of afforested organic soils are scarce and hampered by the uncertainties associated with methodology. In this study we etermined the GHG budget of a spruce-dominated forest on a drained organic soil with an agricultural history. Two different approaches for determining the net ecosystem CO2 exchange (NEE) were applied, for the year 2008, one direct (eddy covariance) and the other indirect (analyzing the different components of the GHG budget), so that uncertainties in each method could be evaluated. The annual tree production in 2008 was 8.3±3.9 tC ha−1 yr−1 due to the high levels of soil nutrients, the favorable climatic conditions and the fact that the forest was probably in its phase of maximum C assimilation or shortly past it. The N2O fluxes were determined by the closed-chamber technique and amounted to 0.9±0.8 tCeq ha−1 yr−1. According to the direct measurements from the eddy covariance technique, the site acts as a minor GHG sink of −1.2±0.8 t Ceq ha−1 yr−1. This contrasts with the NEE estimate derived from the indirect approach which suggests that the site is a net GHG emitter of 0.6±4.5 tCeq ha−1 yr−1. Irrespective of the approach applied, the soil CO2 effluxes counter large amounts of the C sequestration by trees. Due to accumulated uncertainties involved in the indirect approach, the direct approach is considered the more reliable tool. As the rate of C sequestration will likely decrease with forest age, the site will probably become a GHG source once again as the trees do not compensate for the soil C and N losses. Also forests in younger age stages have been shown to have lower C assimilation rates; thus, the overall GHG sink potential of this afforested nutrient-rich organic soil is probably limited to the short period of maximum C assimilation.
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| 7. |
- Sikström, Ulf, et al.
(författare)
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Tillförsel av aska i skog på dikad torvmark i södra Sverige – effekter på skogsproduktion, flöden av växthusgaser, torvegenskaper, markvegetation och grundvattenkemi
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Det finns flera sätt att använda den aska som produceras vid förbränning av skogsbränsle som alternativ till deponering. Ett sätt är att återföra askan till skogen. Förutom att utnyttja aska från skogsbränslen som kompensation för markförsurning och uttagen näring, finns det även en potential att öka skogsproduktionen på dikad torvmark. Det finns dock ett behov av ökade kunskaper om övriga miljöeffekter efter tillförsel av aska på dikad torvmark. Syftet med de här redovisade studierna var att undersöka effekten av asktillförsel på trädens tillväxt, flöden av växthusgaser, torvegenskaper, markvegetation och grundvattenkemi. Studierna utfördes i tre fältförsök (Perstorp, Anderstorp och Skogaryd) i Götaland. Samtliga variabler studerades dock inte i alla försök. Perstorp är en lågproduktiv torvmark som vid försöksstarten hade en plantskog av tall. Där studerades långtidseffekter i torven och på markvegetation 25–26 år efter att 2,5 ton t.s. aska per ha tillförts, troligen som lösaska. Det var stor skillnad i skogstillstånd mellan kontrollytor och askytor vid tidpunkten för dessa studier. Kontrollytorna var i stort sett oförändrade sedan försöksstarten avseende trädskiktet (1,7 m höga träd), medan askytorna hyste en ca 5,5 m hög tallungskog med ca dubbelt så högt stamantal. Anderstorp är en något bördigare lokal med tallskog än Perstorp. Skogaryd är en högproduktiv torvmark med granskog. I båda försöken tillfördes krossaskor i två doser, 3,3 och 6,6 ton t.s. aska per ha. Den lägre dosen kan betraktas som en hög kompensationsgiva alternativt en låg askgödslingsgiva, medan den högre kan ses som en möjlig praktisk askgödslingsgiva. Resultaten från dessa försök belyser effekter upp till fem respektive två år efter asktillförseln. Trädens grundytetillväxt i Anderstorp ökade signifikant efter tillförsel av 6,6 ton t.s. aska ha-1under den studerade femårsperioden. Det var ett förväntat resultat enligt tidigare erfarenheter. I Skogaryd kunde inga tillväxteffekter av asktillförseln påvisas efter två år. De uppmätta gasflödena upp till fem åren efter tillförsel av 3,3 och 6,6 ton t.s. krossaska per ha visade att emissionen av CO2 var oförändrad i Anderstorp. På den bördiga lokalen (Skogaryd) minskade emissionen av CO2. Emissionen av CH4 var oförändrad i båda försöken. Lustgasemissionerna i Anderstorp var knappt detekterbara, medan askan minskade emissionen i Skogaryd. Minskningen tycktes vara kopplad till ökat pH-värde i torven. Den mikrobiella biomassan minskade i de undersökta dränerade lågproduktiva torvmarkerna av en låg askgiva (ca 3 ton d.w. per ha), medan samhällsstrukturen var opåverkad. Asktillförseln minskade nettokvävemineraliseringen i dessa torvmarker. Inga påtagliga initiala förändringar av markvegetationen kunde påvisas efter asktillförseln. Vegetationsstrukturen ändrades på försökslokalen med lägst bördighet (Perstorp) och växtdiversiteten och täckningsgraden i fältskiktet minskade. Detta var troligen en effekt av det förändrade skogstillståndet p.g.a. asktillförseln. Resultaten från torvmarken med hög bördighet och granskog (Skogaryd) visade på en ökad diversitet i både fält- och bottenskikt samt en något ökad produktion i markvegetationen två år efter asktillförseln. Asktillförseln i Skogaryd gav mycket få påvisbara behandlingseffekter för de 43 uppmätta grundvattenkemiska variablerna. De höga bakgrundsnivåerna av bl.a. B, Ca, Mg och PO4-P bidrog sannolikt till detta. En slutsats är att tillförsel av 3–6 ton krossaska ha-1 på dikad torvmark inte bidrar till ökad GWP (”Global Warming Potential”), utan snarare till en minskning, under de fem första åren efter åtgärden. Det krävs mer långsiktiga uppföljningar i försöken för att se om de redovisade effekterna på GWP är bestående samt fördjupade studier för att förstå mekanismerna bakom de uppmätta minskade flödena av CO2 och N2O.
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| 8. |
- Von Arnold, Karin, et al.
(författare)
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Can distribution of trees explain variation in nitrous oxide fluxes?
- 2005
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 20:6, s. 481-489
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Tidskriftsartikel (refereegranskat)abstract
- The impact of distance to tree stems on nitrous oxide (N2O) fluxes was examined to determine whether it is possible to improve the accuracy of flux estimates from boreal forest soils. Dark static chambers were placed along transects between pairs of trees within a Norway spruce stand and fluxes of N2O and carbon dioxide (CO2) were measured during the period 1999-2003. The groundwater table was measured on every sampling occasion along the transects. In addition, radiation transmission, potential diffusion rate and biomass of forest floor vegetation were measured once at each chamber site along one of the transects and soil samples were collected at three depths, from which pH, denitrification enzyme activity, soil moisture, organic matter, and carbon and nitrogen content were determined. There was a high level of variation in the N2O fluxes, both spatially and temporally. However, the spatial variation in the N2O fluxes within the transect could not be explained by differences in any of the measured variables. Sometimes, mainly when no major peaks occurred, N2O fluxes were significantly correlated with CO2 release. It is concluded that distance to stems cannot be used to improve the design of sampling schemes or for extrapolating flux levels to larger scales.
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