| 1. |
- Audet, Joachim, et al.
(författare)
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Forest streams are important sources for nitrous oxide emissions - Nitrous oxide emissions from Swedish streams
- 2020
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26, s. 629-641
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Tidskriftsartikel (refereegranskat)abstract
- Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6 +/- 2.1 and 1.3 +/- 1.8 mu g N/L, respectively (mean +/- SD) despite higher total N (TN) concentrations in agricultural streams (1,520 +/- 1,640 vs. 780 +/- 600 mu g N/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low-order streams at the national scale revealed that ~1.8 x 10(9) g N2O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800 x 10(9) g CO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector.
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| 2. |
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| 3. |
- Futter, Martyn, et al.
(författare)
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Forests, Forestry and the Water Framework Directive in Sweden : A Trans-Disciplinary Commentary
- 2011
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 2:1, s. 261-282
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Tidskriftsartikel (refereegranskat)abstract
- The Water Framework Directive (WFD) is an ambitious piece of legislation designed to protect and improve water quality throughout Europe. However, forests are only mentioned once in the WFD, and forestry is not mentioned at all, despite its potential implications for streams, rivers and lakes. Here we present a transdisciplinary commentary on the WFD and its implications for forests and forestry in Sweden. This commentary has been prepared by forestry stakeholders, biophysical and social scientists. While we were cognizant of a large body of discipline-specific research, there are very few inter-or trans-disciplinary commentaries which link academic and stakeholder perspectives on the WFD. We had originally felt that there would be little commonality in our concerns. However, we found significant areas of agreement. Our key areas of concern about the implications of the WFD for forestry in Sweden included: (i) concerns about what is meant by good ecological status and how it is assessed; (ii) a perceived lack of clarity in the legal framework; (iii) an inadequate environmental impact assessment process; and (iv) uncertainties about appropriate programs of measures for improving water quality. We were also concerned that ecosystem services provided by forests and the positive effects of forestry on water quality are inadequately recognized in the WFD.
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| 4. |
- Gottselig, N., et al.
(författare)
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Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers
- 2017
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 31:10, s. 1592-1607
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Tidskriftsartikel (refereegranskat)abstract
- Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (~1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 ± 5% (Si) and 53 ± 21% (Fe; mean ± SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe- to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.
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| 5. |
- Kritzberg, Emma S., et al.
(författare)
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Browning of freshwaters : Consequences to ecosystem services, underlying drivers, and potential mitigation measures
- 2020
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Ingår i: Ambio: a Journal of the Human Environment. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 49:2, s. 375-390
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Forskningsöversikt (refereegranskat)abstract
- Browning of surface waters, as a result of increasing dissolved organic carbon and iron concentrations, is a widespread phenomenon with implications to the structure and function of aquatic ecosystems. In this article, we provide an overview of the consequences of browning in relation to ecosystem services, outline what the underlying drivers and mechanisms of browning are, and specifically focus on exploring potential mitigation measures to locally counteract browning. These topical concepts are discussed with a focus on Scandinavia, but are of relevance also to other regions. Browning is of environmental concern as it leads to, e.g., increasing costs and risks for drinking water production, and reduced fish production in lakes by limiting light penetration. While climate change, recovery from acidification, and land-use change are all likely factors contributing to the observed browning, managing the land use in the hydrologically connected parts of the landscape may be the most feasible way to counteract browning of natural waters.
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| 6. |
- Schelker, Jakob, et al.
(författare)
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Nitrogen export from a boreal stream network following forest harvesting : seasonal nitrate removal and conservative export of organic forms
- 2016
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 13:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Clear-cutting is today the primary driver of large-scale forest disturbance in boreal regions of Fennoscandia. Among the major environmental concerns of this practice for surface waters is the increased mobilization of nutrients, such as dissolved inorganic nitrogen (DIN) into streams. But while DIN loading to first-order streams following forest harvest has been previously described, the downstream fate and impact of these inputs is not well understood. We evaluated the downstream fate of DIN and dissolved organic nitrogen (DON) inputs in a boreal landscape that has been altered by forest harvests over a 10-year period. The small first-order streams indicated substantial leaching of DIN, primarily as nitrate (NO3-) in response to harvests with NO3- concentrations increasing by similar to 15-fold. NO3- concentrations at two sampling stations further downstream in the network were strongly seasonal and increased significantly in response to harvesting at the mid-sized stream, but not at the larger stream. DIN removal efficiency, E-r, calculated as the percentage of "forestry derived" DIN that was retained within the stream network based on a mass-balance model was highest during the snowmelt season followed by the growing season, but declined continuously throughout the dormant season. In contrast, export of DON from the landscape indicated little removal and was essentially conservative. Overall, net removal of DIN between 2008 and 2011 accounted for similar to 65% of the total DIN mass exported from harvested patches distributed across the landscape. These results high-light the capacity of nitrogen-limited boreal stream networks to buffer DIN mobilization that arises from multiple clear-cuts within this landscape. Further, these findings shed light on the potential impact of anticipated measures to increase forest yields of boreal forests, such as increased fertilization and shorter forest rotations, which may increase the pressure on boreal surface waters in the future.
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| 7. |
- Schelker, Jakob, et al.
(författare)
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Scaling of increased dissolved organic carbon inputs by forest clear-cutting - What arrives downstream?
- 2014
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 508, s. 299-306
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Tidskriftsartikel (refereegranskat)abstract
- Forest clear-cutting has been found to significantly increase concentrations of dissolved organic carbon (DOC) in boreal first-order streams. Here, we address the questions of (1) how the additional inputs of DOC by upstream forest harvesting affect downstream locations within a stream network and (2) what catchment area has to be harvested to cause a significant downstream increase in DOC concentration. We combined the use of primary data from a paired-catchment experiment, clear-cut history of a nested stream network derived from satellite images with a mixing-model approach in order to quantify the importance of upstream clear-cuts on two downstream sites with different catchment sizes. Modeled [DOC] agreed well with the measured concentrations in the smaller, 8.7 km(2) catchment located above a larger wetland area, but discrepancies occurred for the larger 22.9 km(2) catchment located downstream of the wetland. Estimates of the critical area (A(critical)) needed to be harvested to cause a significant impact on downstream DOC concentrations was quantified to be 11% for p < 0.05 and 23-25% for p < 0.001. Our results suggests that (i) increased DOC concentrations induced by forest harvesting affect downstream sites and (ii) additional DOC inputs by harvests have a significant impact on stream water quality, if harvests exceed A(critical). We suggest that the estimates of A(critical) could be used in sensitive river networks to provide harvesting-thresholds. The latter could be implemented into forest planning that includes considerations of the negative impact of clear-cutting on water quality. (C) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Wallin, Marcus, 1979-, et al.
(författare)
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Carbon dioxide and methane emissions of Swedish low-order streams : a national estimate and lessons learnt from more than a decade of observations
- 2018
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Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 3:3, s. 156-167
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Tidskriftsartikel (refereegranskat)abstract
- Low-order streams are suggested to dominate the atmospheric CO2 source of all inland waters. Yet, many large-scale stream estimates suffer from methods not designed for gas emission determination and rarely include other greenhouse gases such as CH4. Here, we present a compilation of directly measured CO2 and CH4 concentration data from Swedish low-order streams (> 1600 observations across > 500 streams) covering large climatological and land-use gradients. These data were combined with an empirically derived gas transfer model and the characteristics of a ca. 400,000 km stream network covering the entire country. The total stream CO2 and CH4 emission corresponded to 2.7 Tg C yr(-1) (95% confidence interval: 2.0-3.7) of which the CH4 accounted for 0.7% (0.02 Tg C yr(-1)). The study highlights the importance of low-order streams, as well as the critical need to better represent variability in emissions and stream areal extent to constrain future stream C emission estimates.
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