| 1. |
- Datry, T., et al.
(författare)
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A global analysis of terrestrial plant litter dynamics in non-perennial waterways
- 2018
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Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 11:7, s. 497-503
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Tidskriftsartikel (refereegranskat)abstract
- Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES), which sometimes cease to flow and can dry completely, is largely ignored although they represent over half the global river network. Substantial amounts of terrestrial plant litter (TPL) accumulate in dry riverbeds and, upon rewetting, this material can undergo rapid microbial processing. We present the results of a global research collaboration that collected and analysed TPL from 212 dry riverbeds across major environmental gradients and climate zones. We assessed litter decomposability by quantifying the litter carbon-to-nitrogen ratio and oxygen (O2) consumption in standardized assays and estimated the potential short-term CO2 emissions during rewetting events. Aridity, cover of riparian vegetation, channel width and dry-phase duration explained most variability in the quantity and decomposability of plant litter in IRES. Our estimates indicate that a single pulse of CO2 emission upon litter rewetting contributes up to 10% of the daily CO2 emission from perennial rivers and stream, particularly in temperate climates. This indicates that the contributions of IRES should be included in global C-cycling assessments.
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| 2. |
- Gomez-Gener, L., et al.
(författare)
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Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions
- 2021
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Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 14, s. 289-294
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27% (0.9 gC m(-2) d(-1)) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65-1.8 PgC yr(-1)) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20-0.55 PgC yr(-1). Failing to account for emission differences between day and night will lead to an underestimate of global CO2 emissions from rivers by up to 0.55 PgC yr(-1), according to analyses of high-frequency CO2 measurements.
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| 3. |
- Shumilova, Oleksandra, et al.
(författare)
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Simulating rewetting events in intermittent rivers and ephemeral streams : A global analysis of leached nutrients and organic matter
- 2019
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Ingår i: Global Change Biology. - : WILEY. - 1354-1013 .- 1365-2486. ; 25:5, s. 1591-1611
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico-chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%-98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events.
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| 4. |
- von Schiller, D., et al.
(författare)
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Sediment Respiration Pulses in Intermittent Rivers and Ephemeral Streams
- 2019
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 33:10, s. 1251-1263
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Tidskriftsartikel (refereegranskat)abstract
- Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32-fold to 66-fold upon sediment rewetting. Structural equation modeling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use, and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2-0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting-drying cycles on respiration and CO2 emissions in stream networks.
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| 5. |
- Lupon, Anna, et al.
(författare)
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Groundwater-stream connections shape the spatial pattern and rates of aquatic metabolism
- 2023
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Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 8:2, s. 350-358
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Tidskriftsartikel (refereegranskat)abstract
- A longstanding challenge in stream ecology is to understand how landscape configuration organizes spatial patterns of ecosystem function via lateral groundwater connections. We combined laboratory bioassays and field additions of a metabolic tracer (resazurin) to test how groundwater-stream confluences, or “discrete riparian inflow points” (DRIPs), regulate heterotrophic microbial activity along a boreal stream. We hypothesized that DRIPs shape spatial patterns and rates of aquatic heterotrophic microbial activity by supplying labile dissolved organic matter (DOM) to streams. Laboratory bioassays showed that the potential influence of DRIPs on heterotrophic activity varied spatially and temporally, and was related to their DOM content and composition. At the reach scale, DRIP-stream confluences elevated the spatial heterogeneity and whole-reach rates of heterotrophic activity, especially during periods of high land–water hydrological connectivity. Collectively, our results show how the arrangement of lateral groundwater connections influence heterotrophic activity in streams with implications for watershed biogeochemical cycles.
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