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  • 1. Agren, A.
    et al.
    Haei, M.
    Kohler, S. J.
    Bishop, Kevin
    Dept. of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, P.O. Box 7050, 750 07 Uppsala, Sweden.
    Laudon, H.
    Regulation of stream water dissolved organic carbon (DOC) concentrations during snowmelt; the role of discharge, winter climate and memory effects2010In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, no 9, p. 2901-2913Article in journal (Refereed)
    Abstract [en]

    Using a 15 year stream record from a northern boreal catchment, we demonstrate that the inter-annual variation in dissolved organic carbon (DOC) concentrations during snowmelt was related to discharge, winter climate and previous DOC export. A short and intense snowmelt gave higher stream water DOC concentrations, as did long winters, while a high previous DOC export during the antecedent summer and autumn resulted in lower concentrations during the following spring. By removing the effect of discharge we could detect that the length of winter affected the modeled soil water DOC concentrations during the following snowmelt period, which in turn affected the concentrations in the stream. Winter climate explained more of the stream water DOC variations than previous DOC export during the antecedent summer and autumn.

  • 2.
    Eugster, W.
    et al.
    ETH Zurich, Institute of Agricultural Sciences.
    DelSontro, T.
    Eawag, Swiss Federal Institute of Aquatic Science and Technology.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Eddy covariance flux measurements confirm extreme CH(4) emissions from a Swiss hydropower reservoir and resolve their short-term variability2011In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 8, no 9, p. 2815-2831Article in journal (Refereed)
    Abstract [en]

    Greenhouse gas budgets quantified via land-surface eddy covariance (EC) flux sites differ significantly from those obtained via inverse modeling. A possible reason for the discrepancy between methods may be our gap in quantitative knowledge of methane (CH(4)) fluxes. In this study we carried out EC flux measurements during two intensive campaigns in summer 2008 to quantify methane flux from a hydropower reservoir and link its temporal variability to environmental driving forces: water temperature and pressure changes (atmospheric and due to changes in lake level). Methane fluxes were extremely high and highly variable, but consistently showed gas efflux from the lake when the wind was approaching the EC sensors across the open water, as confirmed by floating chamber flux measurements. The average flux was 3.8 +/- 0.4 mu g C m(-2) s(-1) (mean +/- SE) with a median of 1.4 mu g C m(-2) s(-1), which is quite high even compared to tropical reservoirs. Floating chamber fluxes from four selected days confirmed such high fluxes with 7.4 +/- 1.3 mu g C m(-2) s(-1). Fluxes increased exponentially with increasing temperatures, but were decreasing exponentially with increasing atmospheric and/or lake level pressure. A multiple regression using lake surface temperatures (0.1 m depth), temperature at depth (10 m deep in front of the dam), atmospheric pressure, and lake level was able to explain 35.4% of the overall variance. This best fit included each variable averaged over a 9-h moving window, plus the respective short-term residuals thereof. We estimate that an annual average of 3% of the particulate organic matter (POM) input via the river is sufficient to sustain these large CH(4) fluxes. To compensate the global warming potential associated with the CH(4) effluxes from this hydropower reservoir a 1.3 to 3.7 times larger terrestrial area with net carbon dioxide uptake is needed if a European-scale compilation of grass-lands, croplands and forests is taken as reference. This indicates the potential relevance of temperate reservoirs and lakes in local and regional greenhouse gas budgets.

  • 3. Gerecht, Andrea
    et al.
    Supraha, Luka
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Edvardsen, Bente
    Probert, Ian
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    High temperature decreases the PIC/POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta)2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, p. 3531-3545Article in journal (Refereed)
    Abstract [en]

    Rising ocean temperatures will likely increase stratification of the water column and reduce nutrient input into the photic zone. This will increase the likelihood of nutrient limitation in marine microalgae, leading to changes in the abundance and composition of phytoplankton communities, which in turn will affect global biogeochemical cycles. Calcifying algae, such as coccolithophores, influence the carbon cycle by fixing CO2 into particulate organic carbon through photosynthesis (POC production) and into particulate inorganic carbon through calcification (PIC production). As calcification produces a net release of CO2, the ratio of PIC to POC production determines whether coccolithophores act as a source (high PIC / POC) or a sink (low PIC / POC) of atmospheric CO2. We studied the effect of phosphorus (P-) limitation and high temperature on the physiology and the PIC / POC ratio of two subspecies of Coccolithus pelagicus. This large and heavily calcified species is a major contributor to calcite export from the photic zone into deep-sea reservoirs. Phosphorus limitation did not influence exponential growth rates in either subspecies, but P-limited cells had significantly lower cellular P-content. One of the subspecies was subjected to a 5 °C temperature increase from 10 °C to 15 °C, which did not affect exponential growth rates either, but nearly doubled cellular P-content under both high and low phosphate availability. This temperature increase reduced the PIC / POC ratio by 40–60%, whereas the PIC / POC ratio did not differ between P-limited and nutrient-replete cultures when the subspecies were grown near their respective isolation temperature. Both P-limitation and elevated temperature significantly increased coccolith malformations. Our results suggest that a temperature increase may intensify P-limitation due to a higher P-requirement to maintain growth and POC production rates, possibly reducing abundances in a warmer ocean. Under such a scenario C. pelagicus may decrease its calcification rate relative to photosynthesis, thus favouring CO2 sequestration over release. It seems unlikely that P-limitation by itself causes changes in the PIC / POC ratio in this species.

  • 4. Gerecht, Andrea
    et al.
    Supraha, Luka
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Univ Oslo, Dept Biosci, Sect Aquat Biol & Toxicol, N-0316 Oslo, Norway.
    Langer, Gerald
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. Univ Oslo, Dept Biosci, Ctr Ecol & Evolutionary Synth, N-0316 Oslo, Norway.
    Phosphorus limitation and heat stress decrease calcification in Emiliania huxleyi2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, p. 833-845Article in journal (Refereed)
    Abstract [en]

    Calcifying haptophytes (coccolithophores) sequester carbon in the form of organic and inorganic cellular components (coccoliths). We examined the effect of phosphorus (P) limitation and heat stress on particulate organic and inorganic carbon (calcite) production in the coccolithophore Emiliania huxleyi. Both environmental stressors are related to rising CO2 levels and affect carbon production in marine microalgae, which in turn impacts biogeochemical cycling. Using semi-continuous cultures, we show that P-limitation and heat stress decrease the calcification rate in E. huxleyi. This could lessen the ballasting effect of coccoliths and weaken carbon export out of the photic zone. However, using batch cultures, we show that different culturing approaches (batch versus semi-continuous) induce different physiologies. This affects the ratio of inorganic (PIC) to organic (POC) carbon and complicates general predictions on the effect of P-limitation on the PIC / POC ratio. Furthermore, heat stress increases P-requirements in E. huxleyi, possibly leading to lower standing stocks in a warmer ocean, especially if this is linked to lower nutrient input. In summary, the predicted rise in global temperature and resulting decrease in nutrient availability may first of all decrease CO2 sequestration by coccolithophores through lower overall carbon production. Secondly, the export of carbon may be diminished by a decrease in calcification and a weaker coccolith ballasting effect.

  • 5.
    Grabs, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Laudon, H.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Lyon, S. W.
    Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden.
    Seibert, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Riparian zone hydrology and soil water total organic carbon (TOC): implications for spatial variability and upscaling of lateral riparian TOC exports2012In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 9, no 10, p. 3901-3916Article in journal (Refereed)
    Abstract [en]

    Groundwater flowing from hillslopes through riparian (near-stream) soils often undergoes chemical transformations that can substantially influence stream water chemistry. We used landscape analysis to predict total organic carbon (TOC) concentration profiles and groundwater levels measured in the riparian zone (RZ) of a 67 km2 catchment in Sweden. TOC exported laterally from 13 riparian soil profiles was then estimated based on the riparian flow-concentration integration model (RIM). Much of the observed spatial variability of riparian TOC concentrations in this system could be predicted from groundwater levels and the topographic wetness index (TWI). Organic riparian peat soils in forested areas emerged as hotspots exporting large amounts of TOC. These TOC fluxes were subject to considerable temporal variations caused by a combination of variable flow conditions and changing soil water TOC concentrations. Mineral riparian gley soils, on the other hand, were related to rather small TOC export rates and were characterized by relatively time-invariant TOC concentration profiles. Organic and mineral soils in RZs constitute a heterogeneous landscape mosaic that potentially controls much of the spatial variability of stream water TOC. We developed an empirical regression model based on the TWI to move beyond the plot scale and to predict spatially variable riparian TOC concentration profiles for RZs underlain by glacial till.

  • 6.
    Granath, Gustaf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Baltzer, Jennifer L.
    Biology Department, Wilfrid Laurier University, Waterloo, Canada.
    Bengtsson, Fia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Boncek, Nicholas
    Department of Biological Sciences, Union College, Schenectady, NY, USA.
    Bragazza, Luca
    Department of Life Science and Biotechnologies, University of Ferrara, Ferrara, Italy; Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, Lausanne, Switzerland; Ecole Polytechnique Fédérale de Lausanne EPFL, School of Architecture, Civil and Environmental Engineering ENAC, Laboratory of ecological systems ECOS, Station 2, Lausanne, Switzerland.
    Bu, Zhao-Jun
    Institute for Peat and Mire Research, Northeast Normal University, State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, Changchun, China; Jilin Provincial Key Laboratory for Wetland Ecological Processes and Environmental Change in the Changbai Mountains, Changchun, China.
    Caporn, Simon J. M.
    School of Science and the Environment, Division of Biology and Conservation Ecology, Manchester Metropolitan University, Manchester, UK.
    Dorrepaal, Ellen
    Climate Impacts Research Centre, Dept. of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Galanina, Olga
    Institute of Earth Sciences, St. Petersburg State University, St. Petersburg, Russia; Komarov Botanical Institute Russian Academy of Sciences, St. Petersburg, Russia.
    Galka, Mariusz
    Laboratory of Wetland Ecology and Monitoring & Department of Biogeography and Paleoecology, Adam Mickiewicz University in Poznan, Poznan, Polen.
    Ganeva, Anna
    Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria.
    Gillikin, David P.
    Department of Geology, Union College, Schenectady, NY, USA.
    Goia, Irina
    Babe ̧s-Bolyai University, Faculty of Biology and Geology, Department of Taxonomy and Ecology, Cluj Napoca, Romania.
    Goncharova, Nadezhda
    Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Science, Syktyvkar, Russia.
    Hajek, Michal
    Masaryk Univ, Fac Sci, Dept Bot & Zool, Brno, Czech Republic.
    Haraguchi, Akira
    Univ Kitakyushu, Dept Biol, Kitakyushu, Fukuoka, Japan.
    Harris, Lorna I.
    McGill Univ, Dept Geog, Montreal, Canada.
    Humphreys, Elyn
    Carleton Univ, Dept Geog & Environm Studies, Ottawa, Canada.
    Jirousek, Martin
    Masaryk Univ, Fac Sci, Dept Bot & Zool, Brno, Czech Republic; Mendel Univ Brno, Fac AgriSci, Dept Plant Biol, Brno, Czech Republic.
    Kajukalo, Katarzyna
    Adam Mickiewicz Univ, Lab Wetland Ecol & Monitoring, Poznan, Poland; Adam Mickiewicz Univ, Dept Biogeog & Paleoecol, Poznan, Poland.
    Karofeld, Edgar
    Univ Tartu, Inst Ecol & Earth Sci, Tartu, Estonia.
    Koronatova, Natalia G.
    Russian Acad Sci, Siberian Branch, Inst Soil Sci & Agrochem, Lab Biogeocenol, Novosibirsk, Russia.
    Kosykh, Natalia P.
    Russian Acad Sci, Siberian Branch, Inst Soil Sci & Agrochem, Lab Biogeocenol, Novosibirsk, Russia.
    Lamentowicz, Mariusz
    Adam Mickiewicz Univ, Lab Wetland Ecol & Monitoring, Poznan, Poland; Adam Mickiewicz Univ, Dept Biogeog & Paleoecol, Poznan, Poland.
    Lapshina, Elena
    Yugra State Univ, Khanty Mansiysk, Russia.
    Limpens, Juul
    Wageningen Univ, Plant Ecol & Nat Conservat Grp, Wageningen, Netherlands.
    Linkosalmi, Maiju
    Finnish Meteorol Inst, Helsinki, Finland.
    Ma, Jin-Ze
    Northeast Normal Univ, State Environm Protect Key Lab Wetland Ecol & Veg, Inst Peat & Mire Res, Changchun, Jilin, Peoples R China; Jilin Prov Key Lab Wetland Ecol Proc & Environm C, Changchun, Jilin, Peoples R China.
    Mauritz, Marguerite
    No Arizona Univ, Dept Biol Sci, Ctr Ecosyst Sci & Soc Ecoss, Flagstaff, USA.
    Munir, Tariq M.
    Univ Calgary, Dept Geog, Calgary, Canada; St Marys Univ, Dept Geol, Calgary, Canada.
    Natali, Susan M.
    Woods Hole Res Ctr, Falmouth, USA.
    Natcheva, Rayna
    Bulgarian Acad Sci, Inst Biodivers & Ecosyst Res, Sofia, Bulgaria.
    Noskova, Maria
    Russian Acad Sci, Komarov Bot Inst, St Petersburg, Russia.
    Payne, Richard J.
    Univ York, Environm, York, N Yorkshire, England; Penza State Univ, Penza, Russia.
    Pilkington, Kyle
    Union Coll, Dept Biol Sci, Schenectady, NY USA.
    Robinson, Sean
    SUNY Coll Oneonta, Dept Biol, Oneonta, NY USA.
    Robroek, Bjorn J. M.
    Univ Southampton, Biol Sci, Southampton, Hants, England.
    Rochefort, Line
    Laval Univ, Dept Plant Sci, Quebec City, PQ, Canada; Laval Univ, Ctr Northern Studies, Quebec City, PQ, Canada.
    Singer, David
    Univ Neuchatel, Inst Biol, Lab Soil Biodivers, Neuchatel, Switzerland; Univ Sao Paulo, Inst Biosci, Dept Zool, Sao Paulo, Brazil.
    Stenoien, Hans K.
    Norwegian Univ Sci & Technol, NTNU Univ Museum, Trondheim, Norway.
    Tuittila, Eeva-Stiina
    Univ Eastern Finland, Sch Forest Sci, Peatland & Soil Ecol Grp, Joensuu, Finland.
    Vellak, Kai
    Univ Tartu, Inst Ecol & Earth Sci, Tartu, Estonia.
    Verheyden, Anouk
    Union Coll, Dept Geol, Schenectady, NY USA.
    Waddington, James Michael
    McMaster Univ, Sch Geog & Earth Sci, Hamilton, Canada.
    Rice, Steven K.
    Union Coll, Dept Biol Sci, Schenectady, NY USA.
    Environmental and taxonomic controls of carbon and oxygen stable isotope composition in Sphagnum across broad climatic and geographic ranges2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 16, p. 5189-5202Article in journal (Refereed)
    Abstract [en]

    Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.), which for their growth depend on nutrients, water and CO2 uptake from the atmosphere. As the isotopic composition of carbon (C-12(,)13) and oxygen (O-16(,)18) of these Sphagnum mosses are affected by environmental conditions, Sphagnum tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is inadequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of Sphagnum is speciesspecific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation) and elevation; (ii) whether the C isotopic signature can be a proxy for net primary productivity (NPP) of Sphagnum; and (iii) to what extent Sphagnum tissue delta O-18 tracks the delta O-18 isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia us ing two important peat-forming Sphagnum species (S. magellanicum, S. fuscum) common to the Holarctic realm. There were differences in delta C-13 values between species. For S. magellanicum delta C-13 decreased with increasing height above the water table (HWT, R-2 = 17 %) and was positively correlated to productivity (R-2 = 7 %). Together these two variables explained 46 % of the between-site variation in delta C-13 values. For S. fuscum, productivity was the only significant predictor of delta C-13 but had low explanatory power (total R-2 = 6 %). For delta O-18 values, approximately 90 % of the variation was found between sites. Globally modelled annual delta O-18 values in precipitation explained 69 % of the between-site variation in tissue delta O-18. S. magellanicum showed lower delta O-18 enrichment than S. fuscum (-0.83 %0 lower). Elevation and climatic variables were weak predictors of tissue delta O-18 values after controlling for delta O-18 values of the precipitation. To summarize, our study provides evidence for (a) good predictability of tissue delta O-18 values from modelled annual delta O-18 values in precipitation, and (b) the possibility of relating tissue delta C-13 values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used on a large scale for climatic reconstructions but that such models should be species-specific.

  • 7.
    Henderiks, Jorijntje
    et al.
    Stockholm University.
    Rickaby, Rosalind E. M.
    Dept. of Earth Sciences, Oxford University, UK.
    A coccolithophore concept for constraining the Cenozoic carbon cycle2007In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 4, no 3, p. 323-329Article in journal (Refereed)
  • 8. Koehler, Birgit
    et al.
    Corre, Marife D.
    Veldkamp, Edzo
    Sueta, Juvia
    Chronic nitrogen addition causes a reduction in soil carbon dioxide efflux during the high-growth period of a tropical montane forest but no response from a tropical lowland forest on a decadal time scale2009In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 6, p. 2973-2983Article in journal (Refereed)
  • 9.
    Koehler, Birgit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Zehe, E.
    Corre, M. D.
    Veldkamp, E.
    An inverse analysis reveals limitations of the soil-CO2 profile method to calculate CO2 production and efflux for well-structured soils2010In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, no 8, p. 2311-2325Article in journal (Refereed)
    Abstract [en]

    Soil respiration is the second largest flux in the global carbon cycle, yet the underlying below-ground process, carbon dioxide (CO2) production, is not well understood because it can not be measured in the field. CO2 production has frequently been calculated from the vertical CO2 diffusive flux divergence, known as 'soil-CO2 profile method'. This relatively simple model requires knowledge of soil CO2 concentration profiles and soil diffusive properties. Application of the method for a tropical lowland forest soil in Panama gave inconsistent results when using diffusion coefficients (D) calculated based on relationships with soil porosity and moisture ('physically modeled' D). Our objective was to investigate whether these inconsistencies were related to (1) the applied interpolation and solution methods and/or (2) uncertainties in the physically modeled profile of D. First, we show that the calculated CO2 production strongly depends on the function used to interpolate between measured CO2 concentrations. Secondly, using an inverse analysis of the soil-CO2 profile method, we deduce which D would be required to explain the observed CO2 concentrations, assuming the model perception is valid. In the top soil, this inversely modeled D closely resembled the physically modeled D. In the deep soil, however, the inversely modeled D increased sharply while the physically modeled D did not. When imposing a constraint during the fit parameter optimization, a solution could be found where this deviation between the physically and inversely modeled D disappeared. A radon (Rn) mass balance model, in which diffusion was calculated based on the physically modeled or constrained inversely modeled D, simulated observed Rn profiles reasonably well. However, the CO2 concentrations which corresponded to the constrained inversely modeled D were too small compared to the measurements. We suggest that, in well-structured soils, a missing description of steady state CO2 exchange fluxes across water-filled pores causes the soil-CO2 profile method to fail. These fluxes are driven by the different diffusivities in inter- vs. intra-aggregate pores which create permanent CO2 gradients if separated by a 'diffusive water barrier'. These results corroborate other studies which have shown that the theory to treat gas diffusion as homogeneous process, a precondition for use of the soil-CO2 profile method, is inaccurate for pore networks which exhibit spatial separation between CO2 production and diffusion out of the soil.

  • 10. Koehler, Birgit
    et al.
    Zehe, Erwin
    Corre, Marife D.
    Veldkamp, Edzo
    An inverse analysis reveals limitations of the soil CO2 profile method to calculate CO2 production and efflux for well-structured soils2010In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, p. 2311-2325Article in journal (Refereed)
  • 11. Ledesma, J. L. J.
    et al.
    Grabs, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Futter, M. N.
    Bishop, Kevin H.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Uppsala Centre for Sustainable Development, CSD Uppsala.
    Laudon, H.
    Koehler, S. J.
    Riparian zone control on base cation concentration in boreal streams2013In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 10, no 6, p. 3849-3868Article in journal (Refereed)
    Abstract [en]

    Riparian zones (RZ) are a major factor controlling water chemistry in forest streams. Base cations' (BC) concentrations, fluxes, and cycling in the RZ merit attention because a changing climate and increased forest harvesting could have negative consequences, including re-acidification, for boreal surface waters. We present a two-year study of BC and silica (Si) flow-weighted concentrations from 13 RZ and 14 streams in different landscape elements of a boreal catchment in northern Sweden. The spatial variation in BC and Si dynamics in both RZ and streams was explained by differences in landscape element type, with highest concentrations in silty sediments and lowest concentrations in peat-dominated wetland areas. Temporal stability in BC and Si concentrations in riparian soil water, remarkably stable Mg/Ca ratios, and homogeneous mineralogy suggest that patterns found in the RZ are a result of a distinct mineralogical upslope signal in groundwater. Stream water Mg/Ca ratios indicate that the signal is subsequently maintained in the streams. Flow-weighted concentrations of Ca, Mg, and Na in headwater streams were represented by the corresponding concentrations in the RZ, which were estimated using the Riparian Flow-Concentration Integration Model (RIM) approach. Stream and RZ flow-weighted concentrations differed for K and Si, suggesting a stronger biogeochemical influence on these elements, including K recirculation by vegetation and retention of Si within the RZ. Potential increases in groundwater levels linked to forest harvesting or changes in precipitation regimes would tend to reduce BC concentrations from RZ to streams, potentially leading to episodic acidification.

  • 12.
    Leith, Fraser Leith
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Dinsmore, Kerry
    Wallin, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Billett, Michael
    Heal, Kate
    Laudon, Hjalmar
    Öquist, Mats
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Carbon dioxide transport across the hillslope–riparian–stream continuum in a boreal headwater catchment2015In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 12, p. 1881-1892Article in journal (Refereed)
  • 13. Limpens, J.
    et al.
    Berendse, F.
    Blodau, C.
    Canadell, J.G.
    Freeman, C.
    Holden, J.
    Roulet, N.
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Schaepman-Strub, G.
    Peatlands and the carbon cycle: from local processes to global implications – a synthesis2008In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 5, no 5, p. 1475-1491Article, review/survey (Refereed)
    Abstract [en]

    Peatlands cover only 3% of the Earth's land surface but boreal and subarctic peatlands store about 15-30% of the world's soil carbon ( C) as peat. Despite their potential for large positive feedbacks to the climate system through sequestration and emission of greenhouse gases, peatlands are not explicitly included in global climate models and therefore in predictions of future climate change. In April 2007 a symposium was held in Wageningen, the Netherlands, to advance our understanding of peatland C cycling. This paper synthesizes the main findings of the symposium, focusing on (i) small-scale processes, (ii) C fluxes at the landscape scale, and (iii) peatlands in the context of climate change.

    The main drivers controlling most are related to some aspects of hydrology. Despite high spatial and annual variability in Net Ecosystem Exchange ( NEE), the differences in cumulative annual NEE are more a function of broad scale geographic location and physical setting than internal factors, suggesting the existence of strong feedbacks. In contrast, trace gas emissions seem mainly controlled by local factors.

    Key uncertainties remain concerning the existence of perturbation thresholds, the relative strengths of the CO2 and CH4 feedback, the links among peatland surface climate, hydrology, ecosystem structure and function, and trace gas biogeochemistry as well as the similarity of process rates across peatland types and climatic zones. Progress on these research areas can only be realized by stronger co-operation between disciplines that address different spatial and temporal scales.

  • 14.
    Manzoni, Stefano
    et al.
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden;Stockholm Univ, Bolin Ctr Climate Res, S-10691 Stockholm, Sweden.
    Capek, Petr
    Pacific Northwest Natl Lab, Environm Mol Sci Lab, Richland, WA USA.
    Porada, Philipp
    Univ Potsdam, Plant Ecol & Nat Conservat, Potsdam, Germany.
    Thurner, Martin
    Stockholm Univ, Bolin Ctr Climate Res, S-10691 Stockholm, Sweden;Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Winterdahl, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Beer, Christian
    Stockholm Univ, Bolin Ctr Climate Res, S-10691 Stockholm, Sweden;Stockholm Univ, Dept Environm Sci & Analyt Chem, S-10691 Stockholm, Sweden.
    Bruchert, Volker
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden.
    Frouz, Jan
    Charles Univ Prague, CUNI Inst Environm Studies, Prague, Czech Republic.
    Herrmann, Anke M.
    Swedish Univ Agr Sci, Dept Soil & Environm, S-75007 Uppsala, Sweden.
    Lindahl, Bjorn D.
    Swedish Univ Agr Sci, Dept Soil & Environm, S-75007 Uppsala, Sweden.
    Lyon, Steve W.
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden;Stockholm Univ, Bolin Ctr Climate Res, S-10691 Stockholm, Sweden.
    Santruckova, Hana
    Univ South Bohemia, Dept Ecosyst Biol, Ceske Budejovice, Czech Republic.
    Vico, Giulia
    Swedish Univ Agr Sci, Dept Crop Prod Ecol, S-75007 Uppsala, Sweden.
    Way, Danielle
    Univ Western Ontario, Dept Biol, London, ON, Canada;Duke Univ, Nicholas Sch Environm, Durham, NC 27708 USA.
    Reviews and syntheses: Carbon use efficiency from organisms to ecosystems - definitions, theories, and empirical evidence2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 19, p. 5929-5949Article, review/survey (Refereed)
    Abstract [en]

    The cycling of carbon (C) between the Earth surface and the atmosphere is controlled by biological and abiotic processes that regulate C storage in biogeochemical compartments and release to the atmosphere. This partitioning is quantified using various forms of C-use efficiency (CUE) - the ratio of C remaining in a system to C entering that system. Biological CUE is the fraction of C taken up allocated to biosynthesis. In soils and sediments, C storage depends also on abiotic processes, so the term C-storage efficiency (CSE) can be used. Here we first review and reconcile CUE and CSE definitions proposed for autotrophic and heterotrophic organisms and communities, food webs, whole ecosystems and watersheds, and soils and sediments using a common mathematical framework. Second, we identify general CUE patterns; for example, the actual CUE increases with improving growth conditions, and apparent CUE decreases with increasing turnover. We then synthesize > 5000CUE estimates showing that CUE decreases with increasing biological and ecological organization - from uni-cellular to multicellular organisms and from individuals to ecosystems. We conclude that CUE is an emergent property of coupled biological-abiotic systems, and it should be regarded as a flexible and scale-dependent index of the capacity of a given system to effectively retain C.

  • 15.
    Mendonça, Raquel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kosten, Sarian
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Cardoso, Simone Jaqueline
    Figueiredo-Barros, Marcos Paulo
    Estrada, Carlos Henrique Duque
    Roland, Fábio
    Organic carbon burial efficiency in a large tropical hydroelectric reservoir2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 11, p. 3331-3342Article in journal (Refereed)
    Abstract [en]

    Hydroelectric reservoirs bury significant amounts of organic carbon (OC) in their sediments. Many reservoirs are characterized by high sedimentation rates, low oxygen concentrations in bottom water and a high share of terrestrially derived OC, and all of these factors have been linked to a high efficiency of OC burial. However, investigations of OC burial efficiency (OCBE, i.e., the ratio between buried and deposited OC) in reservoirs are limited to a few studies, none of which include spatially resolved analyses. In this study we determined the spatial variation in OCBE in a large subtropical reservoir and related it to sediment characteristics. Our results show that the sediment accumulation rate explains up to 92 % of the spatial variability in OCBE, outweighing the effect of other variables, such as OC source and oxygen exposure time. OCBE at the pelagic sites varied from 48 to 86 % (mean 67 %) and decreased towards the dam. At the margins, OCBE was lower (9–17 %) due to the low sediment accumulation in shallow areas. Our data show that the variability in OCBE both along the rivers–dam and the margin–pelagic axes must be considered in whole-reservoir assessments. Combining these results with a spatially resolved assessment of sediment accumulation and OC burial in the studied reservoir, we estimated a spatially resolved mean OC burial efficiency of 57 %. Being the first assessment of OCBE with such a high spatial resolution in a reservoir, these results suggest that reservoirs may bury OC more efficiently than natural lakes.

  • 16.
    Moore, Paul A.
    et al.
    McMaster Univ, Sch Geog & Earth Sci, 1280 Main St West, Hamilton, ON L8S 4K1, Canada.
    Lukenbach, Maxwell C.
    McMaster Univ, Sch Geog & Earth Sci, 1280 Main St West, Hamilton, ON L8S 4K1, Canada;Univ Alberta, Dept Earth & Atmospher Sci, Edmonton, AB T6G 2E3, Canada.
    Thompson, Dan K.
    Nat Resources Canada, Northern Forestry Ctr, Canadian Forest Serv, Edmonton, AB T6H 3S5, Canada.
    Kettridge, Nick
    Univ Birmingham, Sch Geog Earth & Environm Sci, Birmingham B15 2TT, W Midlands, England.
    Granath, Gustaf
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Waddington, James M.
    McMaster Univ, Sch Geog & Earth Sci, 1280 Main St West, Hamilton, ON L8S 4K1, Canada.
    Assessing the peatland hummock-hollow classification framework using high-resolution elevation models: implications for appropriate complexity ecosystem modeling2019In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 16, no 18, p. 3491-3506Article in journal (Refereed)
    Abstract [en]

    The hummock-hollow classification framework used to categorize peatland ecosystem microtopography is pervasive throughout peatland experimental designs and current peatland ecosystem modeling approaches. However, identifying what constitutes a representative hummock-hollow pair within a site and characterizing hummock-hollow variability within or between peatlands remains largely unassessed. Using structure from motion (SfM), high-resolution digital elevation models (DEMs) of hummock-hollow microtopography were used to (1) examine how much area needs to be sampled to characterize site-level microtopographic variation; and (2) examine the potential role of microtopographic shape/structure on biogeochemical fluxes using plot-level data from nine northern peatlands. To capture 95% of site-level microtopographic variability, on average, an aggregate sampling area of 32 m(2) composed of 10 randomly located plots was required. Both site(i.e. transect data) and plot-level (i.e. SfM-derived DEM) results show that microtopographic variability can be described as a fractal at the submeter scale, where contributions to total variance are very small below a 0.5 m length scale. Microtopography at the plot level was often found to be non-bimodal, as assessed using a Gaussian mixture model (GMM). Our findings suggest that the non-bimodal distribution of microtopography at the plot level may result in an undersampling of intermediate topographic positions. Extended to the modeling domain, an underrepresentation of intermediate microtopographic positions is shown to lead to potentially large flux biases over a wide range of water table positions for ecosystem processes which are non-linearly related to water and energy availability at the moss surface. Moreover, our simple modeling results suggest that much of the bias can be eliminated by representing microtopography with several classes rather than the traditional two (i.e. hummock/hollow). A range of tools examined herein can be used to easily parameterize peatland models, from GMMs used as simple transfer functions to spatially explicit fractal landscapes based on simple power-law relations between microtopographic variability and scale.

  • 17. Oni, S. K.
    et al.
    Futter, M. N.
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Kohler, S. J.
    Ottosson-Lofvenius, M.
    Laudon, H.
    Long-term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity2013In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 10, no 4, p. 2315-2330Article in journal (Refereed)
    Abstract [en]

    The boreal landscape is a complex, spatio-temporally varying mosaic of forest and mire landscape elements that control surface water hydrology and chemistry. Here, we assess long-term water quality time series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Acid deposition in this region is low and is further declining. Temporal trends in weather and runoff (1981-2008), dissolved organic carbon concentration [DOC] (1993-2010) and other water quality parameters (1987-2011) were assessed. There was no significant annual trend in precipitation or runoff. However, runoff increased in March and declined in May. This suggested an earlier snowmelt regime in recent years. Significant monotonic increasing trends in air temperature and length of growing season suggested a decrease in snowfall and less spring runoff. Stream [DOC] was positively correlated with some trace metals (copper, iron and zinc) and negatively with several other chemical parameters (e. g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate concentrations during other times of the year were not accompanied by changes in pH and alkalinity. These results indicate subtle effects of recovery from acidification. Water temperature increased significantly both annually and in most months. A simultaneous monotonic increase in iron (Fe) and [DOC] in autumn suggests co-transport of Fe-DOC in the form of organometallic complexes. monotonic increase in UV absorbance in most months without co-occurring changes in DOC trend suggests a shift in DOC quality to a more humic-rich type. The observed increase in soil solution [DOC] and subtle trends in stream [DOC] suggest that climate rather than recovery from acidification is the dominant driver of DOC trends in the Svartberget catchment.

  • 18.
    Parard, Gaelle
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Charantonis, Anastase
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Remote sensing the sea surface CO2 of the Baltic Sea using the SOMLO methodology2015In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 12, p. 3369-3384Article in journal (Refereed)
  • 19.
    Parard, Gaëlle
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Charantonis, A. A.
    Rutgerson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Remote sensing the sea surface CO2 of the Baltic Sea using the SOMLO methodology2015In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 12, no 11, p. 3369-3384Article in journal (Refereed)
    Abstract [en]

    Studies of coastal seas in Europe have noted the high variability of the CO2 system. This high variability, generated by the complex mechanisms driving the CO2 fluxes, complicates the accurate estimation of these mechanisms. This is particularly pronounced in the Baltic Sea, where the mechanisms driving the fluxes have not been characterized in as much detail as in the open oceans. In addition, the joint availability of in situ measurements of CO2 and of sea-surface satellite data is limited in the area. In this paper, we used the SOMLO (self-organizing multiple linear output; Sasse et al., 2013) methodology, which combines two existing methods (i. e. self-organizing maps and multiple linear regression) to estimate the ocean surface partial pressure of CO2 (pCO(2)) in the Baltic Sea from the remotely sensed sea surface temperature, chlorophyll, coloured dissolved organic matter, net primary production, and mixed-layer depth. The outputs of this research have a horizontal resolution of 4 km and cover the 1998-2011 period. These outputs give a monthly map of the Baltic Sea at a very fine spatial resolution. The reconstructed pCO(2) values over the validation data set have a correlation of 0.93 with the in situ measurements and a root mean square error of 36 mu atm. Removing any of the satellite parameters degraded this reconstructed CO2 flux, so we chose to supply any missing data using statistical imputation. The pCO(2) maps produced using this method also provide a confidence level of the reconstruction at each grid point. The results obtained are encouraging given the sparsity of available data, and we expect to be able to produce even more accurate reconstructions in coming years, given the predicted acquisition of new data.

  • 20. Rosen, P.
    et al.
    Bindler, R.
    Korsman, T.
    Mighall, T.
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    The complementary power of pH and lake-water organic carbon reconstructions for discerning the influences on surface waters across decadal to millennial time scales2011In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 8, p. 2439-2466Article in journal (Refereed)
    Abstract [en]

    Lysevatten, a lake in southwest Sweden, has experienced both acidification and recent changes in the amount of lake-water organic carbon (TOC), both causing concern across Europe and North America. A range of paleolimnological tools - diatom-inferred pH, inferred lake-water TOC from visible-near-infrared spectroscopy (VNIRS), multi-element geochemistry and pollen analysis, combined with geochemical modeling were used to reconstruct the lake's chemistry and surroundings back to the most recent deglaciation 12 500 years ago. The results reveal that the recent anthropogenic impacts are similar in magnitude to the long-term variation driven by natural catchment changes and early agricultural land use occurring over centuries and millennia. The combined reconstruction of both lake-water TOC and lithogenic element delivery can explain the major changes in lake-water pH and modeled acid neutralizing capacity during the past 12 500 years. The results raise important questions regarding what precisely comprises "reference" conditions (i.e., free from human impacts) as defined in the European Water Framework Directive.

  • 21.
    Rosenstock, Nicholas P.
    et al.
    Swedish Univ Agr Sci, Uppsala BioCtr, Dept Forest Mycol & Plant Pathol, S-75007 Uppsala, Sweden;Lund Univ, Ctr Environm & Climate Res, S-23262 Lund, Sweden.
    van Hees, Patrick A. W.
    Orebro Univ, Man Technol Environm Res Ctr, S-70182 Orebro, Sweden;Eurofins Environm Testing Sweden AB, S-53117 Lidkoping, Sweden.
    Fransson, Petra M. A.
    Swedish Univ Agr Sci, Uppsala BioCtr, Dept Forest Mycol & Plant Pathol, S-75007 Uppsala, Sweden.
    Finlay, Roger D.
    Swedish Univ Agr Sci, Uppsala BioCtr, Dept Forest Mycol & Plant Pathol, S-75007 Uppsala, Sweden.
    Rosling, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Swedish Univ Agr Sci, Uppsala BioCtr, Dept Forest Mycol & Plant Pathol, S-75007 Uppsala, Sweden.
    Biological enhancement of mineral weathering by Pinus sylvestris seedlings - effects of plants, ectomycorrhizal fungi, and elevated CO22019In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 16, no 18, p. 3637-3649Article in journal (Refereed)
    Abstract [en]

    Better understanding and quantifying the relative influence of plants, associated mycorrhizal fungi, and abiotic factors such as elevated CO2 on biotic weathering is essential to constraining weathering estimates. We employed a column microcosm system to examine the effects of elevated CO2 and Pinus sylvestris seedlings, with or without the ectomycorrhizal fungi Piloderma fallax and Suillus variegatus, on rhizosphere soil solution concentrations of low-molecular-weight organic acids (LMWOAs) and on the weathering of primary minerals. Seedlings significantly increased mineral weathering, as estimated from elemental budgets of Ca, K, Mg, and Si. Elevated CO2 increased plant growth and LMWOA concentrations but had no effect on weathering. Colonization by ectomycorrhizal fungi, particularly P. fallax, showed some tendency to increase weathering. LM-WOA concentrations correlated with seedling biomass across both CO2 and mycorrhizal treatments but not with total weathering. We conclude that nutrient uptake, which reduces transport limitation to weathering, is the primary mechanism by which plants enhanced weathering in this system. While the experimental system used departs from conditions in forest soils in a number of ways, these results are in line with weathering studies performed at the ecosystem, macrocosm, and microcosm scale, indicating that nutrient uptake by plants and microbes is an important biological mechanism by which mineral weathering is enhanced.

  • 22. Réjou-Méchain, M.
    et al.
    Muller-Landau, H. C.
    Detto, M.
    Thomas, S. C.
    Le Toan, T.
    Saatchi, S. S.
    Barreto-Silva, J. S.
    Bourg, N. A.
    Bunyavejchewin, S.
    Butt, N.
    Brockelman, W. Y.
    Cao, M.
    Cárdenas, D.
    Chiang, J. M.
    Chuyong, G. B.
    Clay, K.
    Condit, R.
    Dattaraja, H. S.
    Davies, S. J.
    Duque, A.
    Esufali, S.
    Ewango, C.
    Fernando, R. H. S.
    Fletcher, C. D.
    Gunatilleke, I. A. U. N.
    Hao, Z.
    Harms, K. E.
    Hart, T. B.
    Hérault, B.
    Howe, R. W.
    Hubbell, S. P.
    Johnson, D. J.
    Kenfack, D.
    Larson, A. J.
    Lin, L.
    Lin, Y.
    Lutz, J. A.
    Makana, J. R.
    Malhi, Y.
    Marthews, T. R.
    McEwan, R. W.
    McMahon, S. M.
    McShea, W. J.
    Muscarella, R.
    Nathalang, A.
    Noor, N. S. M.
    Nytch, C. J.
    Oliveira, A. A.
    Phillips, R. P.
    Pongpattananurak, N.
    Punchi-Manage, R.
    Salim, R.
    Schurman, J.
    Sukumar, R.
    Suresh, H. S.
    Suwanvecho, U.
    Thomas, D. W.
    Thompson, J.
    Uríarte, M.
    Valencia, R.
    Vicentini, A.
    Wolf, A. T.
    Yap, S.
    Yuan, Z.
    Zartman, C. E.
    Zimmerman, J. K.
    Chave, J.
    Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 23Article in journal (Refereed)
  • 23. Temnerud, J.
    et al.
    Duker, A.
    Karlsson, S.
    Allard, B.
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Uppsala Centre for Sustainable Development, CSD Uppsala.
    Folster, J.
    Kohler, S.
    Spatial patterns of some trace elements in four Swedish stream networks2013In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 10, no 3, p. 1407-1423Article in journal (Refereed)
    Abstract [en]

    Four river basins in southern Sweden, with catchment sizes from 0.3 to 127 km(2) (median 1.9), were sampled in October 2007. The 243 samples were analysed for 26 trace elements (Ag, As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, Ge, In, La, Li, Mo, Ni, Pb, Sb, Se, Sn, Tl, Ti, U, V and Zn) to identify spatial patterns within drainage networks. The range and median of each element were defined for different stream orders, and relationships to catchment characteristics, including deposition history, were explored. The sampling design made it possible to compare the differences along 40 stream reaches, above and below 53 stream junctions with 107 tributaries and between the 77 inlets and outlets of 36 lakes. The largest concentration differences (at reaches, junctions and lakes) were observed for lakes, with outlets usually having lower concentration compared to the inlets for As, Ba, Be, Bi, Cd, Co, Cr, Ga, Ge, Ni, Pb, Sn, Ti, Tl, U, V and Zn. Significantly lower concentrations were observed for Cd and Co when comparing headwaters with downstream sites in each catchment. Common factor analysis (FA) revealed that As, Bi, Cr, Ga, Ge, Tl and V co-vary positively with Al, Fe and total organic carbon (TOC) and negatively with La, Li and pH. The strong removal of a large number of trace elements when passing through lakes is evident though in the FA, where lake surface coverage plots opposite to many of those elements. Forest volume does not respond in a similar systematic fashion and, surprisingly, the amount of wetland does not relate strongly to either Fe or TOC at any of the rivers. A better understanding of the quantitative removal of organic carbon and iron will aid in understanding trace element fluxes from landscapes rich in organic matter and iron.

  • 24.
    Temnerud, J.
    et al.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden.;Swedish Meteorol & Hydrol Inst, Res Dept, S-60176 Norrkoping, Sweden..
    von Bromssen, C.
    Swedish Univ Agr Sci, Dept Econ, Unit Appl Stat & Math, Uppsala, Sweden..
    Folster, J.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Buffam, I.
    Univ Cincinnati, Dept Biol Sci, Cincinnati, OH USA.;Univ Cincinnati, Dept Geog, Cincinnati, OH USA..
    Andersson, J. -O
    Nyberg, L.
    Karlstad Univ, Ctr Climate & Safety, Karlstad, Sweden..
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Uppsala Centre for Sustainable Development, CSD Uppsala, Centre for Environment and Development Studies. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden..
    Map-based prediction of organic carbon in headwater streams improved by downstream observations from the river outlet2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 2, p. 399-413Article in journal (Refereed)
    Abstract [en]

    In spite of the great abundance and ecological importance of headwater streams, managers are usually limited by a lack of information about water chemistry in these headwaters. In this study we test whether river outlet chemistry can be used as an additional source of information to improve the prediction of the chemistry of upstream headwaters (size < 2 km(2)), relative to models based on map information alone. We use the concentration of total organic carbon (TOC), an important stream ecosystem parameter, as the target for our study. Between 2000 and 2008, we carried out 17 synoptic surveys in 9 mesoscale catchments (size 32-235 km(2)). Over 900 water samples were collected in total, primarily from headwater streams but also including each catchment's river outlet during every survey. First we used partial least square regression (PLS) to model the distribution (median, interquartile range (IQR)) of headwater stream TOC for a given catchment, based on a large number of candidate variables including sub-catchment characteristics from GIS, and measured river chemistry at the catchment outlet. The best candidate variables from the PLS models were then used in hierarchical linear mixed models (MM) to model TOC in individual headwater streams. Three predictor variables were consistently selected for the MM calibration sets: (1) proportion of forested wetlands in the sub-catchment (positively correlated with headwater stream TOC), (2) proportion of lake surface cover in the sub-catchment (negatively correlated with headwater stream TOC), and (3) river outlet TOC (positively correlated with headwater stream TOC). Including river outlet TOC improved predictions, with 5-15% lower prediction errors than when using map information alone. Thus, data on water chemistry measured at river outlets offer information which can complement GIS-based modelling of headwater stream chemistry.

  • 25. Veldkamp, Edzo
    et al.
    Koehler, Birgit
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Corre, Marife
    Indications of nitrogen-limited methane uptake in tropical forest soils2013In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 10, no 8, p. 5367-5379Article in journal (Refereed)
    Abstract [en]

    Abstract: It is estimated that tropical forest soils contribute 6.2 Tg yr(-1) (28 %) to global methane (CH4) uptake, which is large enough to alter CH4 accumulation in the atmosphere if significant changes would occur to this sink. Elevated deposition of inorganic nitrogen (N) to temperate forest ecosystems has been shown to reduce CH4 uptake in forest soils, but almost no information exists from tropical forest soils even though projections show that N deposition will increase substantially in tropical regions. Here we report the results from two long-term, ecosystem-scale experiments in which we assessed the impact of chronic N addition on soil CH4 fluxes from two old-growth forests in Panama: (1) a lowland, moist (2.7 m yr(-1) rainfall) forest on clayey Cambisol and Nitisol soils with controls and N-addition plots for 9-12yr, and (2) a montane, wet (5.5 m yr(-1) rainfall) forest on a sandy loam Andosol soil with controls and N-addition plots for 1-4 yr. We measured soil CH4 fluxes for 4 yr (2006-2009) in four replicate plots (40 m x 40 m each) per treatment using vented static chambers (four chambers per plot). CH4 fluxes from the lowland control plots and the montane control plots did not differ from their respective N-addition plots. In the lowland forest, chronic N addition did not lead to inhibition of CH4 uptake; instead, a negative correlation of CH4 fluxes with nitrate (NO3-) concentrations in the mineral soil suggests that increased NO3- levels in N-addition plots had stimulated CH4 consumption and/or reduced CH4 production. In the montane forest, chronic N addition also showed negative correlation of CH4 fluxes with ammonium concentrations in the organic layer, which suggests that CH4 consumption was N limited. We propose the following reasons why such N-stimulated CH4 consumption did not lead to statistically significant CH4 uptake: (1) for the lowland forest, this was caused by limitation of CH4 diffusion from the atmosphere into the clayey soils, particularly during the wet season, as indicated by the strong positive correlations between CH4 fluxes and water-filled pore space (WFPS); (2) for the montane forest, this was caused by the high WFPS in the mineral soil throughout the year, which may not only limit CH4 diffusion from the atmosphere into the soil but also favour CH4 production; and (3) both forest soils showed large spatial and temporal variations of CH4 fluxes. We conclude that in these extremely different tropical forest ecosystems there were indications of N limitation on CH4 uptake. Based on these findings, it is unlikely that elevated N deposition on tropical forest soils will lead to a rapid reduction of CH4 uptake.

1 - 25 of 25
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