| 1. |
- Ledesma, Jose, et al.
(författare)
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Aquatic DOC export from subarctic Atlantic blanket bog in Norway is controlled by seasalt deposition, temperature and precipitation
- 2016
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 127, s. 305-321
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive and credible peatland carbon budgets, needed for global carbon accounting, must include lateral aquatic organic carbon export. Here, we quantify aquatic dissolved organic carbon (DOC) export for an Atlantic bog in subarctic Norway, the Andøya peatland, and test for sensitivity to climatic drivers. Hydrology, DOC concentrations and DOC export were simulated for 2000–2013 using the process-based catchment model Integrated Catchments model for Carbon(INCA-C), calibrated to site-specific water chemistry and hydrology (2011–2014) using readily-available data on temperature, precipitation and seasalt deposition. Measured streamwater DOC declined under seasalt episodes and was strongly positively related to temperature. Model calibrations successfully reproduced the water balance, variation in runoff (R2=0.67; Nash–Sutcliffe model efficiency NS=0.67) and DOC concentrations (R2=0.85; NS=0.84). The most sensitive model parameters related to temperature-sensitivity of DOC production and DOC (de)sorption sensitivity to seasalts. Model uncertainty related to parameter space was similar to interannual variation in DOC export. Mean annual modelled DOC export was 7.2±0.7g C m−2 year−1, roughly 35% of the net land–atmospheric CO2 exchange at Andøya from 2009 to 2012 (estimated elsewhere). Current and antecedent mean temperature and precipitation were strong drivers of seasonal modelled DOC export, implying that warmer and wetter summers will lead to more DOC export. Evaluation of similar climate impacts on net peatland carbon accumulation requires additional exploration of the climate-sensitivity of land–atmosphere fluxes of CO2 and methane. Process-based models are valuable tools to account for lateral DOC exports in carbon balances of northern peatlands, especially where long-term monitoring data are lacking.
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| 2. |
- Ledesma, Jose, et al.
(författare)
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Boreal forest riparian zones regulate stream sulfate and dissolved organic carbon
- 2016
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 560-561, s. 110-122
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Tidskriftsartikel (refereegranskat)abstract
- In boreal forest catchments, solute transfer to streams is controlled by hydrological and biogeochemical processes occurring in the riparian zone (RZ). However, RZs are spatially heterogeneous and information about solute chemistry is typically limited. This is problematic when making inferences about stream chemistry. Hypothetically, the strength of links between riparian and stream chemistry is time-scale dependent. Using a ten-year (2003-2012) dataset from a northern Swedish catchment, we evaluated the suitability of RZ data to infer stream dynamics at different time scales. We focus on the role of the RZ versus upslope soils in controlling sulfate (SO42-) and dissolved organic carbon (DOC). A priori, declines in acid deposition and redox-mediated SO42- pulses control sulfur (S) fluxes and pool dynamics, which in turn affect dissolved organic carbon (DOC). We found that the catchment is currently a net source of S, presumably due to release of the S pool accumulated during the acidification period. In both, RZ and stream, SO42- concentrations are declining over time, whereas DOC is increasing. No temporal trends in SO42- and DOC were observed in upslope mineral soils. SO42- explained the variation of DOC in stream and RZ, but not in upslope mineral soil. Moreover, as SO42- decreased with time, temporal variability of DOC increased. These observations indicate that: (1) SO42- is still an important driver of DOC trends in boreal catchments and (2) RZ processes control stream SO42- and subsequently DOC independently of upslope soils. These phenomena are likely occurring in many regions recovering from acidification. Because water flows through a heterogeneous mosaic of RZs before entering the stream, upscaling information from limited RZ data to the catchment level is problematic at short-time scales. However, for long-term trends and annual dynamics, the same data can provide reasonable representations of riparian processes and support meaningful inferences about stream chemistry. (C) 2016 The Authors. Published by Elsevier B.V.
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| 3. |
- Oni, Stephen, et al.
(författare)
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Using dry and wet year hydroclimatic extremes to guide future hydrologic projections
- 2016
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 20, s. 2811-2825
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Tidskriftsartikel (refereegranskat)abstract
- There are growing numbers of studies on climate change impacts on forest hydrology, but limited attempts have been made to use current hydroclimatic variabilities to constrain projections of future climatic conditions. Here we used historical wet and dry years as a proxy for expected future extreme conditions in a boreal catchment. We showed that runoff could be underestimated by at least 35% when dry year parameterizations were used for wet year conditions. Uncertainty analysis showed that behavioural parameter sets from wet and dry years separated mainly on precipitation-related parameters and to a lesser extent on parameters related to landscape processes, while uncertainties inherent in climate models (as opposed to differences in calibration or performance metrics) appeared to drive the overall uncertainty in runoff projections under dry and wet hydroclimatic conditions. Hydrologic model calibration for climate impact studies could be based on years that closely approximate anticipated conditions to better constrain uncertainty in projecting extreme conditions in boreal and temperate regions.
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| 4. |
- Oni, Stephen, et al.
(författare)
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Local- and landscape-scale impacts of clear-cuts and climate change on surface water dissolved organic carbon in boreal forests
- 2015
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Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 120:11, s. 2402-2426
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Tidskriftsartikel (refereegranskat)abstract
- Forest harvesting and climate change may significantly increase concentrations and fluxes of dissolved organic carbon (DOC) in boreal surface waters. However, the likely magnitude of any effect will vary depending on the landscape-element type and spatial scale. We used a chain of hydrological, empirical, and process-based biogeochemical models coupled to an ensemble of downscaled Regional Climate Model experiments to develop scenario storylines for local- and landscape-scale effects of forest harvesting and climate change on surface water DOC concentrations and fluxes. Local-scale runoff, soil temperature, and DOC dynamics were simulated for a range of forest and wetland landscape-element types and at the larger landscape scale. The results indicated that climate change will likely lead to greater winter flows and earlier, smaller spring peaks. Both forest harvesting and climate change scenarios resulted in large increases in summer and autumn runoff and higher DOC fluxes. Forest harvesting effects were clearly apparent at local scales. While at the landscape scale, approximately 1 mg L−1 (or 10%) of the DOC in surface waters can be attributed to clear-cuts, both climate change and intensified forestry can each increase DOC concentrations by another 1 mg L−1 in the future, which is less than that seen in many waterbodies recovering from acidification. These effects of forestry and climate change on surface water DOC concentrations are additive at a landscape scale but not at the local scale, where a range of landscape-element specific responses were observed.
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| 5. |
- Peacock, Mike, et al.
(författare)
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Spatial and Seasonal Variations in Dissolved Methane Across a Large Lake
- 2023
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 128:8
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Tidskriftsartikel (refereegranskat)abstract
- Lakes process large volumes of organic carbon (OC), are important sources of methane (CH4), and contribute to climatic warming. However, there is a lack of data from large lakes >500 km(2), which creates uncertainty in global budgets. In this data article, we present dissolved CH4, OC bioreactivity measurements, water chemistry, and algal biovolumes at 11 stations across Lake Malaren, the third largest (1,074 km(2)) Swedish lake. Total phosphorus concentrations show that during the study period the lake was classed as mesotrophic/eutrophic. Overall mean CH4 concentration from all stations, sampled five times to cover seasonal variation, was 2.51 mu g l(-1) (0.98-5.39 mu g l(-1)). There was no significant seasonal variation although ranges were greatest during summer. Concentrations of CH4 were greatest in shallow waters close to anthropogenic nutrient sources, whilst deeper, central basins had lower concentrations. Methane correlated positively with measures of lake productivity (chlorophyll a, total phosphorus), and negatively to water depth and oxygen concentration, with oxygen emerging as the sole significant driver in a linear mixed effects model. We collated data from other lakes >500 km(2) (n = 21) and found a significant negative relationship between surface area and average CH4 concentration. Large lakes remain an understudied contributor to the global CH4 cycle and future research efforts should aim to quantify the spatial and temporal variation in their diffusive and ebullitive emissions, and associated drivers. Plain Language Summary Lakes contribute to climatic warming, because they emit large amounts of the powerful greenhouse gas methane into the atmosphere. This occurs because lake bottom sediments and lake waters are home to microbes that produce methane, which then travels diffusively in a dissolved form, or as bubbles, through the lake water and into the air. There is large uncertainty about how much methane is released by lakes on a global scale, and more measurements are required to reduce this uncertainty, particularly from very large lakes. In our study, we measured dissolved methane from 11 sampling locations across a very large Swedish lake, and repeated this five times over a year. Levels of methane within the lake were generally low, but they varied over space and time. Higher methane levels occurred in shallower waters near large towns and cities, and were associated with greater concentrations of nutrients such as phosphorus, which act as food for the methane-producing microbes.
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| 6. |
- Winterdahl, Mattias, et al.
(författare)
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Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites
- 2011
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:8, s. 920-930
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Tidskriftsartikel (refereegranskat)abstract
- Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at GAyenrdsjon increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20-62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.
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| 7. |
- Peacock, M., et al.
(författare)
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Global importance of methane emissions from drainage ditches and canals
- 2021
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Ingår i: Environmental Research Letters. - : IOP Publishing Ltd. - 1748-9326. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- Globally, there are millions of kilometres of drainage ditches which have the potential to emit the powerful greenhouse gas methane (CH4), but these emissions are not reported in budgets of inland waters or drained lands. Here, we synthesise data to show that ditches spanning a global latitudinal gradient and across different land uses emit large quantities of CH4 to the atmosphere. Area-specific emissions are comparable to those from lakes, streams, reservoirs, and wetlands. While it is generally assumed that drainage negates terrestrial CH4 emissions, we find that CH4 emissions from ditches can, on average, offset similar to 10% of this reduction. Using global areas of drained land we show that ditches contribute 3.5 Tg CH4 yr(-1) (0.6-10.5 Tg CH4 yr(-1)); equivalent to 0.2%-3% of global anthropogenic CH4 emissions. A positive relationship between CH4 emissions and temperature was found, and emissions were highest from eutrophic ditches. We advocate the inclusion of ditch emissions in national GHG inventories, as neglecting them can lead to incorrect conclusions concerning the impact of drainage-based land management on CH4 budgets.
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| 8. |
- Kiessling, Anders, et al.
(författare)
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Musselodling i Östersjön som miljöåtgärd : nya positiva data från tre pågående EU-projekt
- 2019
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Rapport (populärvet., debatt m.m.)abstract
- Nya resultat visar att musselodlingar i Östersjön har en betydande potential att bidra till att minska övergödningen samtidigt som förutsättningar skapas för en cirkulär ekonomi/produktion. För att ta musselodling till nästa nivå krävs dels ytterligare förfining av den nya tekniken, men framförallt fler och i förlängningen också större odlingar samtidigt som vi måste vidareutveckla alla de initiativ som nu pågår hur näringen kan återanvändas i livsmedelssystemet på ett effektivt och ekonomiskt lönsamt sätt.
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| 9. |
- Winterdahl, Mattias, et al.
(författare)
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Riparian soil temperature modification of the relationship between flow and dissolved organic carbon concentration in a boreal stream
- 2011
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Discharge is often strongly correlated to the temporal variability of dissolved organic carbon concentrations ([DOC]) in watercourses. One recently proposed way to model this is the riparian flow-concentration integration model (RIM) concept that accounts for the role of flow pathway control on [DOC] dynamics in streams. However, in boreal systems, there is also commonly a seasonal pattern, which cannot be explained by variability in discharge alone. The objectives with this study were to (1) demonstrate RIM as a tool for studying variability in stream water chemistry, (2) investigate factors related to stream water DOC variability, and (3) modify RIM to account for these factors. RIM was used with 14 years of daily discharge and almost 500 stream measurements of [DOC] from a forested boreal headwater stream. We used the calibrated RIM to account for discharge influences and then investigated variables that could be related to DOC variability (air and soil temperature, soil moisture, precipitation, antecedent flow and stream sulfate). Five alternative formulations of RIM, with temporally varying soil concentration profiles based on the variability in soil temperature and/or antecedent flow, were evaluated. The model where only the effects of riparian soil temperature on dynamics in DOC depth profiles were included performed best overall. This dynamic RIM improved the Nash-Sutcliffe to 0.58 compared to 0.42 for the flow-only formulation and reduced the median absolute error from 3.0 to 2.1 mg L (-1). This study demonstrates that RIM is a simple way of modeling stream DOC and exploring controls on stream water chemistry.
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| 10. |
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