| 1. |
- Corman, Jessica R., et al.
(författare)
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Response of lake metabolism to catchment inputs inferred using high-frequency lake and stream data from across the northern hemisphere
- 2023
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 68:12, s. 2617-2631
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Tidskriftsartikel (refereegranskat)abstract
- In lakes, the rates of gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP) are often controlled by resource availability. Herein, we explore how catchment vs. within lake predictors of metabolism compare using data from 16 lakes spanning 39°N to 64°N, a range of inflowing streams, and trophic status. For each lake, we combined stream loads of dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) with lake DOC, TN, and TP concentrations and high frequency in situ monitoring of dissolved oxygen. We found that stream load stoichiometry indicated lake stoichiometry for C : N and C : P (r2 = 0.74 and r2 = 0.84, respectively), but not for N : P (r2 = 0.04). As we found a strong positive correlation between TN and TP, we only used TP in our statistical models. For the catchment model, GPP and R were best predicted by DOC load, TP load, and load N : P (R2 = 0.85 and R2 = 0.82, respectively). For the lake model, GPP and R were best predicted by TP concentrations (R2 = 0.86 and R2 = 0.67, respectively). The inclusion of N : P in the catchment model, but not the lake model, suggests that both N and P regulate metabolism and that organisms may be responding more strongly to catchment inputs than lake resources. Our models predicted NEP poorly, though it is unclear why. Overall, our work stresses the importance of characterizing lake catchment loads to predict metabolic rates, a result that may be particularly important in catchments experiencing changing hydrologic regimes related to global environmental change.
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| 2. |
- de Wit, Heleen A., et al.
(författare)
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Current Browning of Surface Waters Will Be Further Promoted by Wetter Climate
- 2016
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Ingår i: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS. - : American Chemical Society (ACS). - 2328-8930. ; 3:12, s. 430-435
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Tidskriftsartikel (refereegranskat)abstract
- Browning of surface waters because of increasing terrestrial dissolved organic carbon (OC) concentrations is a concern for drinking water providers and can impact land carbon storage. We show that positive trends in OC in 474 streams, lakes, and rivers in boreal and subarctic ecosystems in Norway, Sweden, and Finland between 1990 and 2013 are surprisingly constant across climatic gradients and catchment sizes (median, +1.4% year(-1); interquartile range, +0.8-2.0% year(-1)), implying that water bodies across the entire landscape are browning. The largest trends (median, +1.7% year(-1)) were found in regions impacted by strong reductions in sulfur deposition, while subarctic regions showed the least browning (median, +0.8% year(-1)). In dry regions, precipitation was a strong and positive driver of OC concentrations, declining in strength moving toward high rainfall sites. We estimate that a 10% increase in precipitation will increase mobilization of OC from soils to freshwaters by at least 30%, demonstrating the importance of climate wetting for the carbon cycle. We conclude that upon future increases in precipitation, current browning trends will continue across the entire aquatic continuum, requiring expensive adaptations in drinking water plants, increasing land to sea export of carbon, and impacting aquatic productivity and greenhouse gas emissions.
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| 3. |
- Moldan, Filip, et al.
(författare)
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NKL-1915 National Nitrogen Budgets in Scandinavia: consequences for climate change and for eutrophication – synthesis report
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents the results of a project undertaken by Norway, Finland, Sweden, and Denmark related to the National Nitrogen Budget (NNB) with a focus on the NNB pool Forests and semi-natural vegetation (FS). The NNB involves calculations of reactive nitrogen (Nr) inflows and outflows within the FS pool, and the study compares these calculations to reports of carbon sequestration in climate reporting to the United Nations Framework Convention on Climate Change (UNFCCC).Norway and Finland initiated their work on NNB, concentrating on Forests and semi-natural vegetation (FS). The UNECE LRTAP Task Force on Reactive Nitrogen (TFRN) methodology was also used for compiling the FS pool for Denmark, while Sweden had established its FS pool prior to the project.The FS pool comprises three sub-pools: forests, wetlands, and other lands. Inflows of reactive nitrogen (Nr) to the FS pool are primarily from deposition and biological N-fixation, with major outflows being leaching, harvest, and denitrification.In Finland, Sweden, and Denmark, the inflows and outflows are in balance, while in Norway, there is an accumulation of Nr, indicating a surplus of nitrogen. Wetland sub-pools in all four countries and the forest sub-pool in Norway show nitrogen accumulation.All four countries report carbon sequestration in forests to UNFCCC.There is a link between nitrogen and carbon cycles, since the organic matter forming the carbon stock in forests and wetlands relies on nitrogen. The origin of nitrogen contributing to the estimated C-stock increase needs further investigation.There is a discrepancy between the calculated nitrogen changes in the FS pool and the nitrogen needed to support reported carbon stock changes. Possible explanations for the discrepancies are re-location of nitrogen within pools, changes in the C/N ratio, expansion of forested areas, and uncertainties in N-fixation rates and denitrification.There is a need for better integration of carbon and nitrogen flux and stock change estimates in natural ecosystems. Understanding the interactions between carbon and nitrogen is deemed crucial for predicting future developments in carbon sequestration and impacts of nitrogen deposition, especially for the Nordic countries with their significant forests playing roles as carbon and nitrogen sinks.
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