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1.	Audet, J., et al. (författare) Forest streams are important sources for nitrous oxide emissions 2020 Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26:2, s. 629-641 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±1.8µgN/L, respectively (mean±SD) despite higher total N (TN) concentrations in agricultural streams (1,520±1,640 vs. 780±600µgN/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 ~1.8×109g 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 800×109gCO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector. © 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd
2.	Abbott, Benjamin, et al. (författare) Using multi-tracer inference to move beyond single-catchment ecohydrology 2016 Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 160, s. 19-42 Tidskriftsartikel (refereegranskat)abstract Protecting or restoring aquatic ecosystems in the face of growing anthropogenic pressures requires an understanding of hydrological and biogeochemical functioning across multiple spatial and temporal scales. Recent technological and methodological advances have vastly increased the number and diversity of hydrological, biogeochemical, and ecological tracers available, providing potentially powerful tools to improve understanding of fundamental problems in ecohydrology, notably: 1. Identifying spatially explicit flowpaths, 2. Quantifying water residence time, and 3. Quantifying and localizing biogeochemical transformation. In this review, we synthesize the history of hydrological and biogeochemical theory, summarize modem tracer methods, and discuss how improved understanding of flowpath, residence time, and biogeochemical transformation can help ecohydrology move beyond description of site-specific heterogeneity. We focus on using multiple tracers with contrasting characteristics (crossing proxies) to infer ecosystem functioning across multiple scales. Specifically, we present how crossed proxies could test recent ecohydrological theory, combining the concepts of hotspots and hot moments with the Damkohler number in what we call the HotDam framework.
3.	Audet, Joachim, et al. (författare) Nitrous oxide emissions from streams in a Swedish agricultural catchment 2017 Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 236, s. 295-303 Tidskriftsartikel (refereegranskat)abstract Excess nitrogen fertiliser in agricultural soils might be leached to streams and converted to the greenhouse gas nitrous oxide (N2O). To assess the importance of N2O emissions from agricultural streams, concentration dynamics and emissions N2O emissions in streams were investigated in a 32 km2 lowland agricultural catchment located in Sweden. Dissolved N2O concentration was measured at nine occasions between December 2014 and August 2015 at nine stream stations. The stream stations represented sub-catchments with different land use characteristics with agricultural land use ranging from 0 to 63% of the area. Stream N2O percentage saturation ranged 40-2701% and showed large spatial and temporal variations. Statistical analysis using mixed models revealed that N2O concentration was significantly linked to nitrate concentration in the stream water, to the percentage arable land in the sub catchments as well as to the stream water discharge. Using two empirical equations to estimate the N2O emissions showed that streams were generally a source of N2O to the atmosphere (mean 108 and 175 mu g N m(-2) h(-1) with first and second equation). The catchment scale estimate of N2O stream emissions was compared to the estimate obtained using IPCC guidelines linking N fertilisation inputs and leaching to N2O emissions. The comparison suggested that N2O stream emission calculated using the IPCC methodology might be underestimated. A coarse estimate suggests that N2O stream emissions represent about 4% of the total N2O emissions from N-fertiliser at the catchment scale. Hence while streams covered only 0.1% of the catchment area they were of disproportionate importance as a source of N2O to the atmosphere.
4.	Campeau, Audrey, et al. (författare) Aquatic export of young dissolved and gaseous carbon from a pristine boreal fen : Implications for peat carbon stock stability 2017 Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 23:12, s. 5523-5536 Tidskriftsartikel (refereegranskat)abstract The stability of northern peatland's carbon (C) store under changing climate is of major concern for the global C cycle. The aquatic export of C from boreal peatlands is recognized as both a critical pathway for the remobilization of peat C stocks as well as a major component of the net ecosystem C balance (NECB). Here, we present a full year characterization of radiocarbon content (14C) of dissolved organic carbon (DOC), carbon dioxide (CO2), and methane (CH4) exported from a boreal peatland catchment coupled with 14C characterization of the catchment's peat profile of the same C species. The age of aquatic C in runoff varied little throughout the year and appeared to be sustained by recently fixed C from the atmosphere (<60 years), despite stream DOC, CO2, and CH4 primarily being sourced from deep peat horizons (2–4 m) near the mire's outlet. In fact, the 14C content of DOC, CO2, and CH4 across the entire peat profile was considerably enriched with postbomb C compared with the solid peat material. Overall, our results demonstrate little to no mobilization of ancient C stocks from this boreal peatland and a relatively large resilience of the source of aquatic C export to forecasted hydroclimatic changes.
5.	Campeau, Audrey, et al. (författare) Autumn destabilization of deep porewater CO2 store in a northern peatland driven by turbulent diffusion 2021 Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1 Tidskriftsartikel (refereegranskat)abstract The deep porewater of northern peatlands stores large amounts of carbon dioxide (CO2). This store is viewed as a stable feature in the peatland CO2 cycle. Here, we report large and rapid fluctuations in deep porewater CO2 concentration recurring every autumn over four consecutive years in a boreal peatland. Estimates of the vertical diffusion of heat indicate that CO2 diffusion occurs at the turbulent rather than molecular rate. The weakening of porewater thermal stratification in autumn likely increases turbulent diffusion, thus fostering a rapid diffusion of deeper porewater CO2 towards the surface where net losses occur. This phenomenon periodically decreases the peat porewater CO2 store by between 29 and 90 g C m−2 throughout autumn, which is comparable to the peatland’s annual C-sink. Our results establish the need to consider the role of turbulent diffusion in regularly destabilizing the CO2 store in peat porewater.
6.	Campeau, Audrey (författare) Carbon in Boreal Streams : Isotopic Tracing of Terrestrial Sources 2019 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The boreal biome comprises vast areas of coniferous forests, dotted with millions of peatlands. Plants harbouring these ecosystems fix CO2 from the atmosphere, which is later incorporated into the vegetation biomass and subsequently buried in soils. Over the course of millennia, this process has led to the formation of a large repository of organic C, currently stored in boreal soils. Streams draining this landscape are typically enriched with carbon dioxide (CO2), methane (CH4) and dissolved organic carbon (DOC). As a consequence, streams tend to emit CO2 and CH4 to the atmosphere, two potent greenhouse gases, and thus contribute positively to radiative climate forcing. The sources fuelling C to boreal streams are not well understood. This thesis aims to unravel these sources, and promote a better consolidation of terrestrial and aquatic C biogeochemical processes. The work is largely based on stable and radiogenic C isotope characterization of various dissolved C forms in stream and groundwater, within contrasting ecosystem types across Sweden.This thesis identifies boreal soils as the main source of CO2 in streams. Soil respiration (i.e. biogenic sources) overwhelmingly supply CO2 to streams, leaving only a few exceptions where geogenic CO2 sources were present. An array of biological processes also transform CO2 during its transport from soils to streams. These include; methanogenesis, aquatic DOC mineralization and primary production. The majority of C in boreal streams is sustained by the decomposition of recent photosynthates, with ancient C substrates holding a negligible share of the total C export. While these results suggest that the repository of ancient soil organic C is currently stable, within boreal forests and peatlands, the close connection with recently occurring photosynthesis suggest that forecasted alterations in plant C allocation patterns, driven by climate and land-use changes, will produce a rapid response in stream CO2 emissions. Isotopic characterization of C in stream and groundwater can help reveal these sources and transformation processes, but its interpretation must be made with care.
7.	Campeau, Audrey, et al. (författare) Multiple sources and sinks of dissolved inorganic carbon across Swedish streams, refocusing the lens of stable C isotopes 2017 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7 Tidskriftsartikel (refereegranskat)abstract It is well established that stream dissolved inorganic carbon (DIC) fluxes play a central role in the global C cycle, yet the sources of stream DIC remain to a large extent unresolved. Here, we explore large-scale patterns in delta C-13-DIC from streams across Sweden to separate and further quantify the sources and sinks of stream DIC. We found that stream DIC is governed by a variety of sources and sinks including biogenic and geogenic sources, CO2 evasion, as well as in-stream processes. Although soil respiration was the main source of DIC across all streams, a geogenic DIC influence was identified in the northernmost region. All streams were affected by various degrees of atmospheric CO2 evasion, but residual variance in delta C-13-DIC also indicated a significant influence of in-stream metabolism and anaerobic processes. Due to those multiple sources and sinks, we emphasize that simply quantifying aquatic DIC fluxes will not be sufficient to characterise their role in the global C cycle.
8.	Campeau, Audrey, et al. (författare) Stable carbon isotopes reveal soil - stream DIC linkages in contrasting headwater catchments 2018 Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 123:1, s. 149-167 Tidskriftsartikel (refereegranskat)abstract Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. While this physical process has been the focus of multiple studies, less is known about the underlying biogeochemical transformations that accompany this transfer of C from soils to streams. Here we used patterns in stream water and groundwater C-13-DIC values within three headwater catchments with contrasting land cover to identify the sources and processes regulating DIC during its transport. We found that although considerable CO2 evasion occurs as DIC is transported from soils to streams, there were also other processes affecting the DIC pool. Methane production and mixing of C sources, associated with different types and spatial distribution of peat-rich areas within each catchment, had a significant influence on the C-13-DIC values in both soils and streams. These processes represent an additional control on C-13-DIC values and the catchment-scale cycling of DIC across different northern landscape types. The results from this study demonstrate that the transport of DIC from soils to streams results in more than just rapid CO2 evasion to the atmosphere but also represents a channel of C transformation, which questions some of our current conceptualizations of C cycling at the landscape scale. Plain Language Summary Large carbon dioxide emission to the atmosphere occurs as rainwater percolates through soils and into streams. This physical process is important for the global carbon cycle and has been the focus of multiple studies. However, less is known about the underlying processes that accompanies this transfer of carbon dioxide from soils to streams. Here we analyze the stable isotope composition of soil and stream carbon dioxide and demonstrate that methane production and mixing of carbon sources also occur in soils and streams. These processes were linked to different types and configurations of peat-rich areas, for example, bogs, fens, and riparian zones, found within each of the three studied catchments. Our results therefore demonstrate that the export of carbon dioxide from soils to streams not only results in emissions to the atmosphere but also represents a channel of transformation. This questions some of our current conceptualization of the catchment-scale cycling of carbon dioxide.
9.	Dinsmore, Kerry, et al. (författare) Contrasting CO2 concentration discharge dynamics in headwater streams : a multi-catchment comparison 2013 Ingår i: Journal of Geophysical Research-Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 118:2, s. 445-461 Tidskriftsartikel (refereegranskat)abstract Aquatic CO2 concentrations are highly variable and strongly linked to discharge, but until recently, measurements have been largely restricted to low-frequency manual sampling. Using new in situ CO2 sensors, we present concurrent, high-frequency (<30 min resolution) CO2 concentration and discharge data collected from five catchments across Canada, UK, and Fennoscandinavia to explore concentration-discharge dynamics; we also consider the relative importance of high flows to lateral aquatic CO2 export. The catchments encompassed a wide range of mean CO2 concentrations (0.73–3.05 mg C L−1) and hydrological flow regimes from flashy peatland streams to muted outflows within a Finnish lake system. In three of the catchments, CO2 concentrations displayed clear bimodal distributions indicating distinct CO2 sources. Concentration-discharge relationships were not consistent across sites with three of the catchments displaying a negative relationship and two catchments displaying a positive relationship. When individual high flow events were considered, we found a strong correlation between both the average magnitude of the hydrological and CO2 response peaks, and the average response lag times. An analysis of lateral CO2 export showed that in three of the catchments, the top 30% of flow (i.e., flow that was exceeded only 30% of the time) had the greatest influence on total annual load. This indicates that an increase in precipitation extremes (greater high-flow contributions) may have a greater influence on the flushing of CO2 from soils to surface waters than a long-term increase in mean annual precipitation, assuming source limitation does not occur.
10.	Guseva, S., et al. (författare) Variable Physical Drivers of Near-Surface Turbulence in a Regulated River 2021 Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:11 Tidskriftsartikel (refereegranskat)abstract Inland waters, such as lakes, reservoirs and rivers, are important sources of climate forcing trace gases. A key parameter that regulates the gas exchange between water and the atmosphere is the gas transfer velocity, which itself is controlled by near-surface turbulence in the water. While in lakes and reservoirs, near-surface turbulence is mainly driven by atmospheric forcing, in shallow rivers and streams it is generated by bottom friction of gravity-forced flow. Large rivers represent a transition between these two cases. Near-surface turbulence has rarely been measured in rivers and the drivers of turbulence have not been quantified. We analyzed continuous measurements of flow velocity and quantified turbulence as the rate of dissipation of turbulent kinetic energy over the ice-free season in a large regulated river in Northern Finland. Measured dissipation rates agreed with predictions from bulk parameters, including mean flow velocity, wind speed, surface heat flux, and with a one-dimensional numerical turbulence model. Values ranged from to . Atmospheric forcing or gravity was the dominant driver of near-surface turbulence for similar fraction of the time. Large variability in near-surface dissipation rate occurred at diel time scales, when the flow velocity was strongly affected by downstream dam operation. By combining scaling relations for boundary-layer turbulence at the river bed and at the air-water interface, we derived a simple model for estimating the relative contributions of wind speed and bottom friction of river flow as a function of depth.Plain Language SummaryInland water bodies such as lakes, reservoirs and rivers are an important source of climate forcing trace gases to the atmosphere. Gas exchange between water and the atmosphere is regulated by the gas transfer velocity and the concentration difference between the water surface and the atmosphere. The gas transfer velocity depends on near-surface turbulence, but robust formulations have not been developed for river systems. Their surface area is sufficiently large for meteorological forcing to cause turbulence, as in lakes and reservoirs, but turbulence generated from bed and internal friction of gravity-driven flows is also expected to contribute. Here we quantify near-surface turbulence using data from continuous air and water side measurements conducted over the ice-free season in a large subarctic regulated river in Finland. We find that turbulence, quantified as the dissipation rate of turbulent kinetic energy, is well described using equations for predicting turbulence from meteorological data for sufficiently high wind speeds whereas the contribution from bottom shear dominated at higher flow velocities. A one-dimensional river model successfully captured these processes. We provide a fundamental model for estimating the relative contributions of atmospheric forcing and bottom friction as a function of depth.
11.	Gutiérrez Loza, Lucia, et al. (författare) Measurement of air-sea methane fluxes in the Baltic Sea using the eddy covariance method 2019 Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 7 Tidskriftsartikel (refereegranskat)abstract Methane (CH4) is the second-most important greenhouse gas in the atmosphere having a significant effect on global climate. The ocean-particularly the coastal regions-have been recognized to be a net source of CH4, however, the constraints on temporal and spatial resolution of CH4 measurements have been the limiting factor to estimate the total oceanic contributions. In this study, the viability of micrometeorological methods for the analysis of CH4 fluxes in the marine environment was evaluated. We present 1 year of semi-continuous eddy covariance measurements of CH4 atmospheric dry mole fractions and air-sea CH4 flux densities at the Ostergarnsholm station at the east coast of the Gotland Island in the central Baltic Sea. The mean annual CH4 flux density was positive, indicating that the region off Gotland is a net source of CH4 to the atmosphere with monthly mean flux densities ranging between -0.1 and 36 nmol m(-2)s(-1). Both the air-water concentration gradient and the wind speed were found to be crucial parameters controlling the flux. The results were in good agreement with other measurements in the Baltic Sea reported in the MEMENTO database. Our results suggest that the eddy covariance technique is a useful tool for studying CH4 fluxes and improving the understanding of air-sea gas exchange processes with high-temporal resolution. Potentially, the high resolution of micrometeorological data can increase the understanding of the temporal variability and forcing processes of CH4 flux.
12.	Gutiérrez-Loza, Lucía (författare) Mechanisms controlling air-sea gas exchange in the Baltic Sea 2020 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Carbon plays a major role in physical and biogeochemical processes in the atmosphere, the biosphere, and the ocean. CO2 and CH4 are two of the most common carbon-containing compounds in the atmosphere, also recognized as major greenhouse gases. The exchange of CO2 and CH4 between the ocean and the atmosphere is an essential part of the global carbon cycle. The exchange is controlled by the air–sea concentration gradient and by the efﬁciency of the transfer processes. The lack of knowledge about the forcing mechanisms affecting the exchange of these climate-relevant gases is a major source of uncertainty in the estimation of the global oceanic contributions. Quantifying and understanding the air–sea exchange processes is essential to constrain the estimates and to improve our knowledge about the current and future climate. In this thesis, the mechanisms controlling the air–sea gas exchange in the Baltic Sea are investigated.The viability of micrometeorological techniques for CH4 monitoring in a coastal environment is evaluated. One year of semi-continuous measurements of air–sea CH4 ﬂuxes using eddy covariance measurements suggests that the method is useful for CH4 ﬂux estimations in marine environments. The measurements allow long-term monitoring at high frequency rates, thus, capturing the temporal variability of the ﬂux. The region off Gotland is a net source of CH4, with both the air–sea concentration gradient and the wind as controlling mechanisms.A sensitivity analysis of the gas transfer velocity is performed to evaluate the effect of the forcing mechanisms controlling the air–sea CO2 exchange in the Baltic Sea. This analysis shows that the spatio-temporal variability of CO2 ﬂuxes is strongly modulated by water-side convection, precipitation, and surfactants. The effect of these factors is relevant both at regional and global scales, as they are not included in the current budget estimates.
13.	Gutiérrez Loza, Lucia, et al. (författare) On physical mechanisms enhancing air-sea CO2 exchange 2022 Ingår i: Biogeosciences. - : European Geosciences Union (EGU). - 1726-4170 .- 1726-4189. ; 19:24, s. 5645-5665 Tidskriftsartikel (refereegranskat)abstract Reducing uncertainties in the air–sea CO2 ﬂux calculations is one of the major challenges when addressing the oceanic contribution in the global carbon balance. In traditional models, the air–sea CO2 ﬂux is estimated using expressions of the gas transfer velocity as a function of wind speed. However, other mechanisms affecting the variability in the ﬂux at local and regional scales are still poorly understood. The uncertainties associated with the ﬂux estimates become particularly large in heterogeneous environments such as coastal and marginal seas. Here, we investigated the air–sea CO2 exchange at a coastal site in the central Baltic Sea using nine years of eddy covariance measurements. Based on these observations we were able to capture the temporal variability of the air–sea CO2 ﬂux and other parameters relevant for the gas exchange. Our results show that a wind-based model with similar pattern to those developed for larger basins and open sea condition can, on average, be a good approximation for k. However, in order to reduce the uncertainty associated to these averages and produce reliable short-term k estimates, additional physical processes must be considered. Using a normalized gas transfer velocity, we identiﬁed conditions associated to enhanced exchange (large k values). During high and intermediate wind speeds (above 6–8 m s−1),conditions on both sides of the air–water interface were found to be relevant for the gas exchange. Our ﬁndings further suggest that at such relatively high wind speeds, sea spray is an efﬁcient mechanisms for air–sea CO2 exchange. During low wind speeds (<6 m s−1), water-side convection was found to be a relevant control mechanism. The effect of both sea spray and water-side convection on the gas exchange showed a clear seasonality with positive ﬂuxes (winter conditions) being the most affected.
14.	Hawkes, Jeffrey A., et al. (författare) Regional diversity of complex dissolved organic matter across forested hemiboreal headwater streams 2018 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1 Tidskriftsartikel (refereegranskat)abstract Dissolved organic matter (DOM) from soils enters the aquatic environment via headwater streams. Thereafter, it is gradually transformed, removed by sedimentation, and mineralised. Due to the proximity to the terrestrial source and short water residence time, the extent of transformation is minimal in headwaters. DOM has variable composition across inland waters, but the amount of variability in the terrestrial end member is unknown. This gap in knowledge is crucial considering the potential impact large variability would have on modelling DOM degradation. Here, we used a novel liquid chromatography –mass spectrometry method to characterise DOM in 74 randomly selected, forested headwater streams in an 87,000 km2 region of southeast Sweden. We found a large degree of sample similarity across this region, with Bray-Curtis dissimilarity values averaging 8.4 ± 3.0% (mean ± SD). The identified variability could be reduced to two principle coordinates, correlating to varying groundwater flow-paths and regional mean temperature. Our results indicate that despite reproducible effects of groundwater geochemistry and climate, the composition of DOM is remarkably similar across catchments already as it leaves the terrestrial environment, rather than becoming homogeneous as different headwaters and sub-catchments mix.
15.	Hedegärd, Marcus, 1979, et al. (författare) Adaptive Hysteresis Compensation Using Reduced Memory Sequences 2017 Ingår i: IEEE/ASME Transactions on Mechatronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1083-4435 .- 1941-014X. ; 22:5, s. 2296-2307 Tidskriftsartikel (refereegranskat)abstract Hysteresis in sensors and actuators can often be effectively compensated for by implementing an inverse hysteresis model in series with the sensor or the actuator. However, an apparent problem enters when the hysteresis characteristics vary over time in an unpredicted manner. Here, we derive an adaptive hysteresis compensation method for the case when we only have observations that are very sparse in time and magnitude. Contrary to previous methods it is based on reduced memory sequences and a preidentified initial model, which makes it possible to use only a few adaption parameters. In particular, we investigate the Preisach model (PM). Using a Bernstein polynomial basis for the PM, it is shown that invertibility translates into linear constraints, which ensures that the overall identification problem for the initial PM is convex. The dependence on PM initial conditions may have negative effects on hysteresis compensation and model adaptation. We give general conditions for losing this dependence and also an upper bound for the maximum error it may cause. The method is experimentally applied to a sensor for measurement of torque in a shaft. At times, the shaft is unloaded and consequently the torque can then be independently observed as being zero. This kind of problem leads to a nonlinear parameterization, but with very few parameters to update, which is successfully achieved using an extended Kalman filter. The method essentially removes the effects of hysteresis, fatigue, and aging for the intended use of the sensor.
16.	Holgersson, Marcus, 1983, et al. (författare) Closing Open Innovation 2024 Ingår i: Strategic Management Review. - 2688-2639 .- 2688-2612. ; In Press Tidskriftsartikel (refereegranskat)abstract The literature on open innovation has documented how companies expand their boundaries to become more open, leaving out how boundaries narrow as open innovation relationships end—the closing of open innovation. We explain how open innovation creates new relationships on multiple levels—among firms, individuals, and technologies. Drawing on open innovation and alliance literature, we discuss how the closing of open innovation entails the dissolution of this web of multiplex relationships. We contribute to innovation and strategy literature by explaining how the closing decision is not simply mirroring the initial decision to open up innovation, partly because of evolving interdependencies at multiple levels (firms, individuals, and technologies). Finally, we discuss how closing open innovation relates to new challenges in terms of attention, agency, long-lived interdependencies, and portfolio management that provide new avenues for future research.
17.	Johnson, Mark S., et al. (författare) Direct and continuous measurements of dissolved carbon dioxide in freshwater aquatic systems : method and applications 2010 Ingår i: Ecohydrology. - : Wiley. - 1936-0584 .- 1936-0592. ; 3:1, s. 68-78 Tidskriftsartikel (refereegranskat)abstract Understanding of the processes that control CO2 concentrations in the aquatic environment has been hampered by the absence of a direct method to make continuous measurements over both short- and long-term time intervals. We describe an in situ method in which a non-dispersive infrared (NDIR) sensor is enclosed in a water impermeable, gas permeable polytetrafluoroethylene (PTFE) membrane and deployed in a freshwater environment. This allows measurements of CO2 concentration to be made directly at a specific depth in the water column without the need for pumps or reagents. We demonstrate the potential of the method using examples from different aquatic environments characterized by a range of CO2 concentrations (0·5–8·0 mg CO2-C l−1, equivalent to ca 40–650 µmol CO2 l−1). These comprise streams and ponds from tropical, temperate and boreal regions. Data derived from the sensor was compared with direct measurements of CO2 concentrations using headspace analysis. Sensor performance following long-term (>6 months) field deployment conformed to manufacturers' specifications, with no drift detected. We conclude that the sensor-based method is a robust, accurate and responsive method, with a wide range of potential applications, particularly when combined with other in situ sensor-based measurements of related variables.
18.	Kokic, Jovana, et al. (författare) Carbon dioxide evasion from headwater systems strongly contributes to the total export of carbon from a small boreal lake catchment 2015 Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 120:1, s. 13-28 Tidskriftsartikel (refereegranskat)abstract Inland waters are hotspots for carbon (C) cycling and therefore important for landscape C budgets. Small streams and lakes are particularly important; however, quantifying C fluxes is difficult and has rarely been done for the entire aquatic continuum, composed of connected streams and lakes within the same catchment. We investigated carbon dioxide (CO2) evasion and fluvial fluxes of dissolved inorganic carbon and dissolved organic carbon (DIC and DOC) in stream and lake systems within the 2.3km(2) catchment of a small boreal lake. Our results show pronounced spatial and temporal variability in C fluxes even at a small spatial scale. C loss from the catchment through CO2 evasion from headwaters for the total open water-sampling period was 9.7g C m(-2) catchment, dominating the total catchment C loss (including CO2 evasion, DIC, and DOC export from the lake, which were 2.7, 0.2, and 5.2g C m(-2) catchment, respectively). Aquatic CO2 evasion was dominated by headwater streams that occupy similar to 0.1% of the catchment but contributed 65% to the total aquatic CO2 evasion from the catchment. The importance of streams was mainly an effect of the higher gas transfer velocities than compared to lakes (median, 67 and 2.2cmh(-1), respectively). Accurately estimating the contribution of C fluxes from headwater streams, particularly the temporal and spatial dynamics in their gas transfer velocity, is key to landscape-scale C budgets. This study demonstrates that CO2 evasion from headwaters can be the major pathway of C loss from boreal catchments, even at a small spatial scale.
19.	Kokic, Jovana, et al. (författare) High spatial variability of gas transfer velocity in streams revealed by turbulence measurements 2018 Ingår i: Inland Waters. - : Taylor & Francis. - 2044-2041 .- 2044-205X. ; 8:4, s. 461-473 Tidskriftsartikel (refereegranskat)abstract Streams are major sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere, but current large-scale estimates are associated with high uncertainties because knowledge concerning the spatiotemporal control on stream emissions is limited. One of the largest uncertainties derives from the choice of gas transfer velocity (k(600)), which describes the physical efficiency of gas exchange across the water-atmosphere interface. This study therefore explored the variability in k(600 )and subsequent CO2 and CH4 emission rates within and across streams of different stream order (SO). We conducted, for the first time in streams, direct turbulence measurements using an acoustic Doppler velocimeter (ADV) to determine the spatial variability in k(600) across a variety of scales with a consistent methodology. The results show high spatial variability in k(600) and corresponding CO2 and CH4 emissions at small spatial scales, both within stream reaches and across SO, especially during high discharge. The k(600) was positively related to current velocity and Reynolds number. By contrast, no clear relationship was found between k(600) and specific stream characteristics such as width and depth, which are parameters often used in empirical models of k(600). Improved understanding of the small-scale variability in the physical properties along streams, especially during high discharge, is therefore an important step to reduce the uncertainty in existing gas transfer models and emissions for stream systems. The ADV method was a useful tool for revealing spatial variability in this work, but it needs further development. We recommend that future studies conduct measurements over shorter time periods (e.g., 10-15 min instead of 40 min) and at more sites across the reach of interest, and thereby derive more reliable mean-reach k(600) as well as more information about controls on the spatial variability in k(600).
20.	Leach, Jason, et al. (författare) Research Spotlight (S. Hall) : Headwater streams may export more carbon than previously thought 2016 Annan publikation (populärvet., debatt m.m.)
21.	Müller, Jens Daniel, et al. (författare) Cyanobacteria net community production in the Baltic Sea as inferred from profiling pCO2 measurements 2021 Ingår i: Biogeosciences. - : European Geosciences Union (EGU). - 1726-4170 .- 1726-4189. ; 18:17, s. 4889-4917 Tidskriftsartikel (refereegranskat)abstract Organic matter production by cyanobacteria blooms is a major environmental concern for the Baltic Sea, as it promotes the spread of anoxic zones. Partial pressure of carbon dioxide (pCO2) measurements carried out on Ships of Opportunity (SOOP) since 2003 have proven to be a powerful tool to resolve the carbon dynamics of the blooms in space and time. However, SOOP measurements lack the possibility to directly constrain depth-integrated net community production (NCP) in moles of carbon per surface area due to their restriction to the sea surface. This study tackles the knowledge gap through (1) providing an NCP best guess for an individual cyanobacteria bloom based on repeated profiling measurements of pCO2 and (2) establishing an algorithm to accurately reconstruct depth-integrated NCP from surface pCO2 observations in combination with modelled temperature profiles.Goal (1) was achieved by deploying state-of-the-art sensor technology from a small-scale sailing vessel. The low-cost and flexible platform enabled observations covering an entire bloom event that occurred in July–August 2018 in the Eastern Gotland Sea. For the biogeochemical interpretation, recorded pCO2 profiles were converted to C∗T, which is the dissolved inorganic carbon concentration normalised to alkalinity. We found that the investigated bloom event was dominated by Nodularia and had many biogeochemical characteristics in common with blooms in previous years. In particular, it lasted for about 3 weeks, caused a C∗T drawdown of 90 µmol kg−1, and was accompanied by a sea surface temperature increase of 10 ∘C. The novel finding of this study is the vertical extension of the C∗T drawdown up to the compensation depth located at around 12 m. Integration of the C∗T drawdown across this depth and correction for vertical fluxes leads to an NCP best guess of ∼1.2 mol m−2 over the productive period.Addressing goal (2), we combined modelled hydrographical profiles with surface pCO2 observations recorded by SOOP Finnmaid within the study area. Introducing the temperature penetration depth (TPD) as a new parameter to integrate SOOP observations across depth, we achieve an NCP reconstruction that agrees to the best guess within 10 %, which is considerably better than the reconstruction based on a classical mixed-layer depth constraint.Applying the TPD approach to almost 2 decades of surface pCO2 observations available for the Baltic Sea bears the potential to provide new insights into the control and long-term trends of cyanobacteria NCP. This understanding is key for an effective design and monitoring of conservation measures aiming at a Good Environmental Status of the Baltic Sea.
22.	Natchimuthu, Sivakiruthika, et al. (författare) Spatio-temporal patterns of stream methane and carbon dioxide emissions in a hemiboreal catchment in Southwest Swedend 2017 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7 Tidskriftsartikel (refereegranskat)abstract Global stream and river greenhouse gas emissions seem to be as large as the oceanic C uptake. However, stream and river emissions are uncertain until both spatial and temporal variability have been quantified. Here we investigated in detail the stream CH4 and CO2 emissions within a hemiboreal catchment in Southwest Sweden primarily covered by coniferous forest. Gas transfer velocities (k(600)), CH4 and CO2 concentrations were measured with multiple methods. Our data supported modelling approaches accounting for various stream slopes, water velocities and discharge. The results revealed large but partially predictable spatio-temporal variabilities in k(600), dissolved gas concentrations, and emissions. The variability in CO2 emission was best explained by the variability in k, while dissolved CH4 concentrations explained most of the variability in CH4 emission, having implications for future measurements. There were disproportionately large emissions from high slope stream reaches including waterfalls, and from high discharge events. In the catchment, stream reaches with low slope and time periods of moderate discharge dominated (90% of area and 69% of time). Measurements in these stream areas and time periods only accounted for <36% of the total estimated emissions. Hence, not accounting for local or episodic high emissions can lead to substantially underestimated emissions.
23.	Nilsson, Erik, 1983-, et al. (författare) Evaluating humidity and sea salt disturbances on CO2 flux measurements 2018 Ingår i: Journal of Atmospheric and Oceanic Technology. - 0739-0572 .- 1520-0426. ; 35, s. 859-875 Tidskriftsartikel (refereegranskat)abstract Global oceans are an important sink of atmospheric carbon dioxide (CO2). Therefore, understanding the air-sea flux of CO2 is a vital part in describing the global carbon balance. Eddy covariance (EC) measurements are often used to study CO2 fluxes from both land and ocean. CO2 are usually measured with infrared absorption sensors, which at the same time measure water vapor. Studies have shown that presence of water vapor fluctuations in the sampling air potentially result in erroneous CO2 flux measurements due to cross-sensitivity of the sensor. Here we compare measured CO2 fluxes from both enclosed path Li-Cor 7200 sensors and open-path Li-Cor 7500 instruments from an inland measurement site and a marine site. We also introduce new quality control criteria based upon a Relative Signal Strength Indicator (RSSI). The sampling gas in one of the Li-Cor 7200 instruments was dried by means of a multi-tube diffusion dryer so that the water vapor fluxes were close to zero. With this setup we investigated the effect that cross-sensitivity of the CO2 signal to water vapor can have on the CO2 fluxes. The dryer had no significant effect on the CO2 fluxes. We tested the hypothesis that the cross-sensitivity effect is caused by hygroscopic particles such as sea salt by spraying a saline solution on the windows of the Li-Cor 7200 instruments during the inland field test. Our results confirm earlier findings that sea salt contamination can affect CO2 fluxes significantly and confirm earlier findings, that drying the sampling air for the gas analyzer is an effective method to reduce this signal contamination.
24.	Nydahl, Anna C., et al. (författare) Groundwater carbon within a boreal catchment : spatiotemporal variability of a hidden aquatic carbon pool 2020 Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:1 Tidskriftsartikel (refereegranskat)abstract Groundwater is an essential resource providing water for societies and sustaining surface waters. Although groundwater at intermediate depth could be highly influential at regulating lake and river surface water chemistry, studies quantifying organic and inorganic carbon (C) species in intermediate depth groundwater are still rare. Here, we quantified dissolved and gaseous C species in the groundwater of a boreal catchment at 3- to 20-m depth. We found that the partial pressure of carbon dioxide (pCO(2)), the stable carbon isotopic composition of dissolved inorganic carbon (delta C-13-DIC), and pH showed a dependency with depth. Along the depth profile, a negative relationship was observed between pCO(2) and delta C-13-DIC and between pCO(2) and pH. We attribute the negative pCO(2)-pH relationship along the depth gradient to increased silicate weathering and decreased soil respiration. Silicate weathering consumes carbon dioxide (CO2) and release base cations, leading to increased pH and decreased pCO(2). We observed a positive relationship between delta C-13-DIC and depth, potentially due to diffusion-related fractionation in addition to isotopic discrimination during soil respiration. Soil CO2 may diffuse downward, resulting in a fractionation of the delta C-13-DIC. Additionally, the dissolved organic carbon at greater depth may be recalcitrant consisting of old degraded material with a greater fraction of the heavier C isotope. Our study provides increased knowledge about the C biogeochemistry of groundwater at intermediate depth, which is important since these waters likely contribute to the widespread CO2 oversaturation in boreal surface waters.
25.	Nydahl, Anna, et al. (författare) Colored organic matter increases CO2 in meso-eutrophic lake water through altered light climate and acidity 2019 Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 64:2, s. 744-756 Tidskriftsartikel (refereegranskat)abstract Many surface waters across the boreal region are browning due to increased concentrations of colored allochthonous dissolved organic carbon (DOC). Browning may stimulate heterotrophic metabolism, may have a shading effect constraining primary production, and may acidify the water leading to decreased pH with a subsequent shift in the carbonate system. All these effects are expected to result in increased lake water carbon dioxide (CO2) concentrations. We tested here these expectations by assessing the effects of both altered allochthonous DOC input and light conditions through shading on lake water CO2 concentrations. We used two mesocosm experiments with water from the meso‐eutrophic Lake Erken, Sweden, to determine the relative importance of bacterial activities, primary production, and shifts in the carbonate system on CO2 concentrations. We found that DOC addition and shading resulted in a significant increase in partial pressure of CO2 (pCO2) in all mesocosms. Surprisingly, there was no relationship between bacterial activities and pCO2. Instead the experimental reduction of light by DOC and/or shading decreased the photosynthesis to respiration ratio leading to increased pCO2. Another driving force behind the observed pCO2 increase was a significant decrease in pH, caused by a decline in photosynthesis and the input of acidic DOC. Considering that colored allochthonous DOC may increase in a warmer and wetter climate, our results could also apply for whole lake ecosystems and pCO2 may increase in many lakes through a reduction in the rate of photosynthesis and decreased pH.

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