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- Thiere, Geraldine, et al.
(författare)
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Nitrogen retention versus methane emission : Environmental benefits and risks of large-scale wetland creation
- 2011
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Ingår i: Ecological Engineering. - : Elsevier. - 0925-8574 .- 1872-6992. ; 37:1, s. 6-15
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Tidskriftsartikel (refereegranskat)abstract
- Coastal eutrophication by nutrient fluxes from agricultural land to marine recipients is presently combated by measures such as the implementation of watershed-scale wetland creation programs aimed at nitrogen removal. Such created agricultural wetlands – termed ‘nitrogen farming wetlands’ (NFWs) – receive nitrogen (N) loads predominantly as nitrate, facilitating N removal by denitrification. However, the conversion of agricultural soils into waterlogged wetland area is likely to increase climate gas emissions, particularly methane (CH4). There is thus a need to evaluate the benefits and risks of wetland creation at a large, watershed-scale. Here we investigate N retention and CH4 emission originating from watershed-scale wetland creation in South Sweden, the relation between both processes, and how CH4 emission depends on individual wetland parameters. We combine data from intensively studied reference wetlands with an extensive wetland survey to predict N retention and CH4 emission with simple models, to estimate the overall process rates (large-scale effects) as well as spatial variation among individual NFWs. We show that watershed-scale wetland creation serves targeted environmental objectives (N retention), and that CH4 emission is comparably low. Environmental benefit and risk of individual wetlands were not correlated, and may thus be managed independently. High cover of aquatic plants was the most important wetland property that suppressed CH4 net production, potentially facilitating N retention simultaneously. Further, differences between wetlands in water temperature and wetland age seemed to contribute to differences in CH4 net production. The nationally planned wetland creation (12,000 ha) could make a significant contribution to the targeted reduction of N fluxes (up to 27% of the Swedish environmental objective), at an environmental risk equaling 0.04% of the national anthropogenic climate gas emission.
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| 2. |
- Thiere, Geraldine, et al.
(författare)
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Uppföljning och förslag på restaurering av anlagda våtmarker i Kalmar kommun
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Den 30 mars 2012 beviljade Länsstyrelsen i Kalmarbidrag till Kalmar kommun för det lokala vattenvårdsprojektet ”Uppföljning och restaurering av våtmarker i Kalmar kommun”. Projektet genomfördes under perioden 25 mars – 30 november i samarbete med miljöanalytiker Jonas Nilsson vid Havsmiljöinstitutets enhet vid Linnéuniversitetet och våtmarksexpert Geraldine Thiere. Delar av projektet genomfördes som ett examensarbete i miljövetenskap av Jessica Olofsson, Linnéuniversitetet. En bedömning visade att majoriteten av de inventerade våtmarkerna ur näringsretentionssynpunkt inte var placerade på optimala ställen. Flera hade till exempel en alldeles för liten andel åkermark i tillrinningsområdet. Andra var placerade för långt från recipienten. Även den lokala utformningenav respektive våtmark kunde i många fall varit bättre. Flera våtmarker var till exempel utformade så att vattenytans form ledde till låg hydraulisk effektivitet. Listan över negativ kritik i rapporten är visserligen lång, men den visar samtidigt att det finns stor utvecklingspotential vid anläggning av nya närsaltsfällor i Kalmar län.
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| 3. |
- Weisner, Stefan E.B., et al.
(författare)
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Effects of vegetation state on biodiversity and nitrogen retention in created wetlands : a test of the biodiversity–ecosystem functioning hypothesis
- 2010
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Ingår i: Freshwater Biology. - Oxford : Blackwell Publishing. - 0046-5070 .- 1365-2427. ; 55:2, s. 387-396
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Tidskriftsartikel (refereegranskat)abstract
- 1. Nitrogen retention in wetlands provides an example of an ecosystem function that is desired by human society, and is a rationale for the creation of wetlands to decrease nitrogen fluxes from nitrate-loaded river catchments to coastal waters.2. Here, we tested the impact of different vegetation states on species diversity and nitrogen retention during 4 years in surface-flow wetlands receiving nitrate-rich water. Tall emergent vegetation or submerged vegetation was introduced to six experimental wetlands each and six wetlands were left as unplanted controls for free development of vegetation. This resulted in three vegetation states dominated by emergent vegetation, by a mixture of submerged vegetation and filamentous green algae or by filamentous green algae.3. Species diversity (species richness and Shannon diversity) of plants was initially lowest in free development wetlands, but during the study became lower in the emergent vegetation wetlands than in the other wetlands. Diversity of macroinvertebrates was initially lower in the submerged vegetation wetlands than in the other wetlands, but this difference disappeared during the study. Nitrogen retention was consistently higher in emergent vegetation wetlands than in the other wetlands throughout the study.4. We conclude that plant diversity in wetlands dominated by tall emergent vegetation gradually became lower than in other wetlands, due to dominant species competitively excluding other plants. However, these wetlands were more efficient at removing nitrogen than those dominated by filamentous algae or submerged macrophytes.5. Management of wetlands often aims to decrease the dominance of tall emergent vegetation for the benefit of plant species diversity and habitat heterogeneity. Our results demonstrate a biodiversity benefit, but also show that this strategy may decrease the ability of wetlands to remove nitrogen. In this case, there is no support for the hypothesis that biodiversity enhances ecosystem function.
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