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  • 51.
    Ask, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Net ecosystem production in clear-water and brown-water lakes2012In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 26, p. GB1017-Article in journal (Refereed)
    Abstract [en]

    We studied 15 lakes in northern Sweden with respect to primary production and respiration in benthic and pelagic habitats. The lakes were characterized by different concentrations of colored dissolved organic carbon (DOC) of terrestrial origin, forming a gradient ranging from clear-water to brown-water lakes. Primary production decreased and respiration increased on a whole-lake scale along the gradient of increasing DOC. Thus, the lakes became more net heterotrophic, i.e., had lower net ecosystem production (NEP = gross primary production - community respiration), with increasing terrestrial DOC and this change coincided with increasing partial pressure of carbon dioxide (pCO(2)) in the surface waters. The single most important process for the increasing net heterotrophy along the DOC gradient was pelagic respiration of terrestrial organic carbon. In spite of high metabolic activity in the benthic habitat, benthic primary production and benthic respiration decreased simultaneously with increasing DOC, showing that the benthic habitat was in metabolic balance throughout the gradient. Therefore, the net heterotrophic states of the lakes depended on the terrestrial DOC export to lakes and the concomitant respiration of terrestrial organic carbon in the pelagic habitat.

  • 52. Asplund, Johan
    et al.
    Johansson, Otilia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nybakken, Line
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gauslaa, Yngvar
    Simulated nitrogen deposition influences gastropod grazing in lichens2010In: Ecoscience, ISSN 1195-6860, Vol. 17, no 1, p. 83-89Article in journal (Refereed)
    Abstract [en]

    Lichens are often important photosynthetic organisms in oligotrophic environments where high-quality fodder plants are rare. A strong herbivore defence and/or low nutritional quality allows the accumulation of a high lichen biomass in such areas. However, it is not known how N deposition influences lichen palatability. This study analyzes possible changes in gastropod grazing preference after 3 months simulated N deposition on 3 foliose (Lobaria scrobiculata, Platismatia glauca, and Xanthoria aureola) and 1 pendulous lichen species (Alectoria sarmentosa). Lichens were daily irrigated in the field with rainwater containing 1.625 mM NH4NO3 from June to September, equivalent to a deposition of 50 kg N·ha-1·y-1. Irrigations applied at night, morning, or noon simulated different C-gain regimes. Afterwards in the lab, we offered 2 common lichen-feeding gastropods the choice between N-fertilized thalli and control thalli irrigated with artificial rainwater. The gastropods clearly preferred the unfertilized thalli of the 3 foliose species. For the pendulous A. sarmentosa, the gastropods preferred N-enriched thalli (irrigated at night) to controls. In conclusion, N-enrichment changes the palatability of lichens in species-specific ways.

  • 53.
    Assefa, Anteneh Taye
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sobek, Anna
    Sundqvist, Kristina L.
    Cato, Ingemar
    Jonsson, Per
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wiberg, Karin
    Temporal Trends of PCDD/Fs in Baltic Sea Sediment Cores Covering the 20th Century2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 2, p. 947-953Article in journal (Refereed)
    Abstract [en]

    The pollution trend of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea region was studied based on depth profiles of PCDD/Fs in sediment cores collected from six offshore areas, eight coastal sites impacted by industrial/urban emissions, and one coastal reference site. A general trend was observed for the offshore and coastal reference sites with substantial increase in PCDD/F concentrations in the mid-late 1970s and peak levels during 1985-2002. The overall peak year for PCDD/Fs in Baltic Sea offshore areas was estimated (using spline-fit modeling) to 1994 ± 5 years, and a half-life in sediments was estimated at 29 ± 11 years. For the industrial/urban impacted coastal sites, the temporal trend was more variable with peak years occurring 1-2 decades earlier compared to offshore areas. The substantial reductions from peak levels (38 ± 11% and 81 ± 12% in offshore and coastal areas, respectively) reflect domestic and international actions taken for reduction of the release of PCDD/Fs to the environment. The modeled overall half-life and reductions of PCDD/Fs in offshore Baltic Sea sediment correspond well to both PCDD/F trends in European lakes without any known direct PCDD/F sources (half-lives 30 and 32 years), and previously modeled reduction in atmospheric deposition of PCDD/Fs to the Baltic Sea since 1990. These observations support previous findings of a common diffuse source, such as long-range air transport of atmospheric emissions, as the prime source of PCDD/Fs to the Baltic Sea region. The half-life of PCDD/Fs in Baltic Sea offshore sediments was estimated to be approximately 2 and 4-6 times longer than in semirural and urban European air, respectively. This study highlights the need for further international actions to reduce the levels of PCDD/Fs in Baltic Sea air specifically and in European air in general.

  • 54. Atkinson, Lindsey J
    et al.
    Campbell, Catherine D
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Zaragoza-Castells, Joana
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Atkin, Owen K
    Impact of growth temperature on scaling relationships linking photosynthetic metabolism to leaf functional traits2010In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 24, no 6, p. 1181-1191Article in journal (Refereed)
    Abstract [en]

    1. Scaling relationships linking photosynthesis (A) to leaf traits are important for predicting vegetation patterns and plant-atmosphere carbon fluxes. Here, we investigated the impact of growth temperature on such scaling relationships.

    2. We assessed whether changes in growth temperature systematically altered the slope and/or intercepts of log-log plots of A vs leaf mass per unit leaf area (LMA), nitrogen and phosphorus concentrations for 19 contrasting plant species grown hydroponically at four temperatures (7, 14, 21 and 28 degrees C) in controlled environment cabinets. Responses of 21 degrees C-grown pre-existing (PE) leaves experiencing a 10 day growth temperature (7, 14, 21 and 28 degrees C) treatment, and newly-developed (ND) leaves formed at each of the four new growth temperatures, were quantified. Irrespective of the growth temperature treatment, rates of light-saturated photosynthesis (A) were measured at 21 degrees C.

    3. Changes in growth temperature altered the scaling between A and leaf traits in pre-existing (PE) leaves, with thermal history accounting for up to 17% and 31% of the variation on a mass and area basis, respectively. However, growth temperature played almost no role in accounting for scatter when comparisons were made of newly-developed (ND) leaves that form at each growth temperature.

    4. Photosynthetic nitrogen and phosphorus use efficiency (PNUE and PPUE, respectively) decreased with increasing LMA. No systematic differences in temperature-mediated reductions in PNUE or PPUE of PE leaves were found among species.

    5. Overall, these results highlight the importance of leaf development in determining the effects of sustained changes in growth temperature on scaling relationships linking photosynthesis to other leaf traits.

  • 55. Aufgebauer, Anne
    et al.
    Panagiotopoulos, Konstantinos
    Wagner, Bernd
    Schaebitz, Frank
    Viehberg, Finn A.
    Vogel, Hendrik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Zanchetta, Giovanni
    Sulpizio, Roberto
    Leng, Melanie J.
    Damaschke, Magret
    Climate and environmental change in the Balkans over the last 17 ka recorded in sediments from Lake Prespa (Albania/FYR of Macedonia/Greece)2012In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 274, p. 122-135Article in journal (Refereed)
    Abstract [en]

    This paper presents sedimentological, geochemical, and biological data from Lake Prespa (Albania/Former Yugoslav Republic of Macedonia/Greece). The 320 cm core sequence (Co1215) covers the last 17 ka calBP and reveals significant change in climate and environmental conditions on a local and regional scale. The sediment record suggests typical stadial conditions from 17.1 to 15.7 ka calBP, documented through low lake productivity, well-mixed conditions, and cold-resistant steppe catchment vegetation. Warming is indicated from 15.7 ka calBP with slightly increased in-lake productivity, gradual expansion of trees, and decreasing erosion through disappearance of local ice caps. Between 14.5 and 11.5 ka calBP relatively stable hydrological conditions are documented. The maximum in tree taxa percentages during the Bolling/Allerod interstadial (14.5-13.2 ka calBP) indicates increased temperatures and moisture availability, whereas the increase of cold-resistant open steppe vegetation taxa percentages during the Younger Dryas (13.2-11.5 ka calBP) is coupled with distinct colder and drier conditions. The Holocene sequence from 11.5 ka calBP indicates ice-free winters, stratification of the water column, a relatively high lake trophic level and dense vegetation cover over the catchment. A strong climate related impact on the limnology and physical parameters in Lake Prespa is documented around 8.2 ka through a significant decrease in productivity, enhanced mixing, strong decomposition and soil erosion, and a coeval expansion of herbs implying cool and dry climate conditions. Intensive human activity in the catchment is indicated from around 1.9 ka calBP. This multiproxy approach improves our understanding of short- and long-term climate fluctuations in this area and their impact on catchment dynamics, limnology, hydrology, and vegetation. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.

  • 56.
    Augulyte, Lijana
    Umeå University, Faculty of Science and Technology, Chemistry.
    Use and Development of Diffusive Samplers to Analyse the Fate of Polycyclic Aromatic Compounds, Polychlorinated Biphenyls and Pharmaceuticals in Wastewater Treatment Processes2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The efficiency of wastewater treatment systems is commonly measured by the reductions of parameters such as biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) and/or reductions in levels of selected macro compounds (e.g. long-chained hydrocarbons and inorganic compounds). Less attention has generally been paid to micropollutants with high potential toxic effects, such as polycyclic aromatic compounds (PACs), including unsubstituted and alkylated polycyclic aromatic hydrocarbons (PAHs) and dibenzothiophenes, polychlorinated biphenyls (PCBs), human pharmaceuticals and by-products formed during the treatment process. These organic micropollutants occur in wastewaters at trace and ultra-trace levels, therefore their detection requires advanced, costly analyses and large sample volumes. Furthermore, concentrations of micropollutants can fluctuate widely both diurnally and between days. Thus, in order to understand the fate of micropollutants in wastewaters there is a need to develop sampling techniques that allow representative samples to be readily collected.

    In the work underlying this thesis two types of diffusive passive samplers, semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCISs), were used to monitor non-polar and polar organic micropollutants in wastewaters subjected to various treatment processes. The pollutants sequestered in these samplers represent micropollutants in the dissolved phase that are available for aquatic organisms. Further, since they collect pollutants in an integrative manner, i.e. they sample continuously during the selected exposure time (usually approx. one to ca. three weeks), the results provide time-weighted average (TWA) concentrations. In addition, the effects of various environmental factors on the uptake of analyzed micropollutants in POCISs and SPMDs were investigated using laboratory calibration and in situ calibration with performance reference compounds (PRCs).

    The results confirm that SPMDs are good sampling tools for investigating the efficacy of wastewater treatment processes for removing non-polar PACs and PCBs, and the effects of varying the process settings. In addition, analyses of process streams in municipal sewage treatment plants demonstrated that conventional sewage treatment processes are not optimized for removing dissolved four-ringed PAHs, some of the five-ringed PAHs, and tri- to hexa-chlorinated biphenyls. The removal of bioavailable PACs was enhanced by adding sorbents with high sorption capacities to the sludge used in the activated sludge treatment step, and a biologically activated carbon system was designed that robustly removed bioavailable PACs, with removal efficiencies of 96.9-99.7 percent across the tested ranges of five varied process parameters.

    In situ SPMD calibration data acquired show that uptake of PACs, described by SPMD sampling rates (Rs), were four to eight times higher than published laboratory calibrated Rs values, mainly due to strong (bio)fouling and turbulence effects. In addition, the laboratory calibration study demonstrated that temperature affects the POCIS uptake of pharmaceuticals. The uptake of four pharmaceuticals was higher, by 10-56 percent, at 18 °C compared to 5 °C. For two of the pharmaceuticals our data indicate that the uptake was lower by 18-25 percent at 18 °C. Our results also indicate that uptake of the studied pharmaceuticals was in the linear phase throughout the 35 day exposure period at both temperatures. Finally, calibration studies enabled aqueous concentrations of micropollutants to be more accurately estimated from amounts collected in the passive samplers.

  • 57.
    Augulyte, Lijana
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kliaugaite, Daina
    Racys, Viktoras
    Jankunaite, Dalia
    Zaliauskiene, Audrone
    Bergqvist, Per-Anders
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Patrik L
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multivariate analysis of a biologically activated carbon (BAC) system and its efficiency for removing PAHs and aliphatic hydrocarbons from wastewater polluted with petroleum products2009In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 170, no 1, p. 103-110Article in journal (Refereed)
    Abstract [en]

    The efficiency of a biologically activated carbon system for treating wastewater polluted with petroleum products was examined and the effects of process parameters on its efficacy were evaluated. In each experiment 17 alkylated and 19 non-alkylated polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs, C10-C40) were extracted using semipermeable membrane devices from wastewater before and after treatment. The acquired data during experiments were analyzed using principal component analysis (PCA). The treatment system robustly removed dissolved PAHs across the studied ranges of the process parameters, providing overall removal efficiencies of 96.9-99.7% for the sum of 36 PAHs. However, the major contributor to their removal was sorption rather than biodegradation, and despite the general efficiency of the process there was up to a 9-fold range in the sums of quantified PAHs in the effluents between experiments. Combinations of long process contact time (24 h) with high temperature (24 degrees C) and moderate oxygen concentration (6-7mg O2 L-1) resulted in good removal of bioavailable PAHs. The removal of TPHs was more dependent on biological activities during the wastewater treatment, and consequently more dependent on the process parameters. In addition, small but significant proportions of PAHs were volatilized and released during the wastewater treatment.

  • 58.
    Aurell, Johanna
    Umeå University, Faculty of Science and Technology, Chemistry.
    Effects of Varying Combustion Conditions on PCDD/F Formation2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are by-products emitted from combustion sources such as municipal solid waste (MSW) incineration plants. These organic compounds are recognized as toxic, bioaccumulative and persistent in the environment. PCDD/Fs are removed from flue gases before released from MSW incineration. However, the PCDD/Fs are not destroyed but retained in the residues, thus in the environment. Understanding the pathways that lead to their formation is important in order to develop ways to suppress their formation and prevent their release into the environment. Suppressing the formation can also allow less expensive air pollution control system to be used, and/or the costs of thermally treating the residues to be reduced. The main objective of the studies underlying this thesis was to elucidate process, combustion and fuel parameters that substantially affect the emission levels and formation of PCDD/Fs in flue gases from MSW incineration. The experiments were conducted under controllable, realistic combustion conditions using a laboratory-scale reactor combusting artificial MSW.

    The parameter found to most strongly reduce the PCDD/F emissions, was prolonging the flue gas residence time at a relatively high temperature (460°C). Increasing the sulfur dioxide (SO2) to hydrogen chloride (HCl) ratio to 1.6 in the flue gas was also found to reduce the PCDF levels, but not the PCDD levels. Fluctuations in the combustion process (carbon monoxide peaks), high chlorine levels in the waste (1.7%) and low temperatures in the secondary combustion zone (660°C) all tended to increase the emission levels. The PCDD/PCDF ratio in the flue gas was found to depend on the chlorine level in the waste, fluctuations in the combustion process and the SO2:HCl ratio in the flue gas. The formation pathways were found to be affected by the quench time profiles in the post-combustion zone, fluctuations in the combustion process and addition of sulfur. In addition, increased levels of chlorine in the waste increased the chlorination degrees of both PCDDs and PCDFs. A tendency for increased SO2 levels in the flue gas to increase levels of polychlorinated dibenzothiophenes (sulfur analogues of PCDFs) was also detected, however the increases were much less significant than the reduction in PCDF levels.

  • 59. Avagyan, Rozanna
    et al.
    Nyström, Robin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindgren, Robert
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerholm, Roger
    Particulate hydroxy-PAH emissions from a residential wood log stove using different fuels and burning conditions2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 140, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Hydroxylated polycyclic aromatic hydrocarbons are oxidation products of polycyclic aromatic hydrocarbons, but have not been studied as extensively as polycyclic aromatic hydrocarbons. Several studies have however shown that hydroxylated polycyclic aromatic hydrocarbons have toxic and carcinogenic properties. They have been detected in air samples in semi urban areas and combustion is assumed to be the primary source of those compounds. To better understand the formation and occurrence of particulate hydroxylated polycyclic aromatic hydrocarbons from residential wood log stove combustion, 9 hydroxylated polycyclic aromatic hydrocarbons and 2 hydroxy biphenyls were quantified in particles generated from four different types of wood logs (birch, spruce, pine, aspen) and two different combustion conditions (nominal and high burn rate). A previously developed method utilizing liquid chromatography photo ionization tandem mass spectrometry and pressurized liquid extraction was used. Polycyclic aromatic hydrocarbons were analyzed along with hydroxylated polycyclic aromatic hydrocarbons. The hydroxylated polycyclic aromatic hydrocarbon emissions varied significantly across different wood types and burning conditions; the highest emissions for nominal burn rate were from spruce and for high burn rate from pine burning. Emissions from nominal burn rate corresponded on average to 15% of the emissions from high burn rate, with average emissions of 218 mu g/MJ(fuel) and 32.5 mu g/MJ(fuel) for high burn rate and nominal burn rate, respectively. Emissions of the measured hydroxylated polycyclic aromatic hydrocarbons corresponded on average to 28% of polycyclic aromatic hydrocarbons emissions. This study shows that wood combustion is a large emission source of hydroxylated polycyclic aromatic hydrocarbons and that not only combustion conditions, but also wood type influences the emissions of hydroxylated polycyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons. There are few studies that have determined hydroxylated polycyclic aromatic hydrocarbons in emissions from wood combustion, and it is therefore necessary to further investigate the formation, occurrence and distribution of these compounds as they are present in significant amounts in wood smoke particles.

  • 60.
    Avenius, Joel
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Agricultural history and its effect on Lake Ekoln, central Sweden: A study based on historical maps and the use of sediment as a proxy for lake-water phosphorus2015Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Agriculture and the use of arable land have long been assumed to be one of the key drivers behind eutrophication of lakes. However, little is known about how early agriculture has affected lakes in the past. The aims of this study were: i) quantify the within-region variability in historical land use and its linkage to soil cover and ii) test if the sediment geochemistry could be used to reconstruct inputs of phosphorus from early agricultural activities. The within-region variability was determined by digitalizing historical maps covering four centuries from the 18th to the 21st century for six selected regions across Sweden. To assess historical changes in lake-water phosphorus, a 6 m long 14C-dated sediment core from Ekoln was analyzed. The core was analyzed for 24 elements by X-ray fluorescence spectroscopy (XRF) together with the total concentration of nitrogen and carbon and their isotopes (δ13C, δ15N). Results show that there was a statistically significant difference (P<0.05) in agricultural activities between regions with soils rich in fine texture classes compared to soils with a more coarse texture. Agriculture also became less dependent on fine-grained soils due to new technological implements following the industrialization. The reconstructed long term-trend in Ekoln indicate limited inputs of phosphorus from early farming and that the lake had higher concentrations of phosphorus throughout the last millennia. Therefore, early farming was unlikely to be the prime driver of high phosphorus loadings, and that other factors should be considered, e.g. extensive urbanization and inputs of wastewater effluent.

  • 61.
    Avenius, Joel
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sänkta sjöars inverkan på ytvatten i Västerbottens kustland: Samband mellan sänkningsnivåer och vattenkemi i sjöar på sulfidrika sedimentjordar2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Lake lowering in sulphide-rich areas is currently a major environmental impact for surface water. This study focuses on whether there is a relationship between a gradient of lake lowering and surface water impacts in areas of sulphide-rich sediments, in order to better understand their contribution of heavy metals and sulfuric acid. Also, is it a reasonable method to use the reduced lake area in order to quantify the gradient? The survey was conducted by collecting water samples from reference lakes and lowered lakes from south to north in coastal areas within the county of Västerbotten. Water samples were then analyzed for TOC, pH, conductivity, anions, base cations, alkalinity, acidity, sulfate, Al, Cd, Fe, Mn, Cu, Zn and Pb. These parameters were then compared statistically using regression analysis and t-tests. The results show that no gradient was discernible in response to the reduced lake area. However, significant differences (p < 0,05) between the reference lakes and all the reduced lakes were visible for pH, conductivity, Cd, Cu, Zn and Al. The study shows that there is a correlation between lake lowering and negative impacts on surface water. However, to calculate a gradient from the reduced lake area is deficient as it is limited by the lakes volume reduction, and how the area around the lake has been affected. Further studies on the subject are therefore necessary.

  • 62. Axelsson, E. Petter
    et al.
    Hjalten, Joakim
    LeRoy, Carri J.
    Whitham, Thomas G.
    Julkunen-Tiitto, Riitta
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Leaf litter from insect-resistant transgenic trees causes changes in aquatic insect community composition2011In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 48, no 6, p. 1472-1479Article in journal (Refereed)
    Abstract [en]

    1. Recent research has addressed how transgenic residues fromarable crops may influence adjacent waterways, aquatic consumers and important ecosystem processes such as litter breakdown rates. With future applications of transgenic plants in forestry, such concerns may apply to forest stream ecosystems. Before any large-scale release of genetically modified (GM) trees, it is therefore imperative to evaluate the effects of genetic modifications in trees on such ecosystems. 2. We conducted decomposition experiments under natural stream conditions using leaf litter from greenhouse grown GM trees (Populus tremula x Populus tremuloides) that express Bacillus thuringiensis (Bt) toxins (cry3Aa; targeting coleopteran leaf-feeding beetles) to examine the hypothesis that GM trees would affect litter decomposition rates and/or the aquatic arthropod community that colonizes and feeds on leaf litter in streams. 3. We show that two independent transformations of isogenic Populus trees to express Bt toxins caused similar changes to the composition of aquatic insects colonizing the leaf litter, ultimately manifested in a 25% and 33% increases in average insect abundance. 4. Measurements of 24 phenolic compounds as well as nitrogen (N) and carbon (C) in the litter did not significantly differ among modified and wild-type trees and were thus not sufficient to explain these differences in the insect assemblage. 5. Decomposition rates were comparable among litter treatments suggesting that the normal suite of leaf traits influencing decomposition was similar among litter treatments and that the shredding functions of the community were maintained despite the changes in insect community composition. 6. Synthesis and applications. We report that leaf litter from GM trees affected the composition of aquatic insect communities that colonized litter under natural stream conditions. This suggests that forest management using GM trees may affect adjacent waterways in unanticipated ways, which should be considered in future commercial applications of GM trees. We also argue that studies at different scales (e.g. species, communities and ecosystems) will be needed for a full understanding of the environmental effects of Bt plants.

  • 63. Axelsson, E Petter
    et al.
    Hjältén, Joakim
    LeRoy, Carri J
    Julkunen-Tiitto, Riitta
    Wennström, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pilate, Gilles
    Can leaf litter from genetically modified trees affect aquatic ecosystems?2010In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 13, no 7, p. 1049-1059Article in journal (Refereed)
    Abstract [en]

    In addition to potential benefits, biotechnology in silviculture may also be associated with environmental considerations, including effects on organisms associated with the living tree and on ecosystems and processes dependent on tree residue. We examined whether genetic modification of lignin characteristics (CAD and COMT) in Populus sp. affected leaf litter quality, the decomposition of leaf litter, and the assemblages of aquatic insects colonizing the litter in three natural streams. The decomposition of leaf litter from one of the genetically modified (GM) lines (CAD) was affected in ways that were comparable over streams and harvest dates. After 84 days in streams, CAD-litter had lost approximately 6.1% less mass than the non-GM litter. Genetic modification also affected the concentration of phenolics and carbon in the litter but this only partially explained the decomposition differences, suggesting that other factors were also involved. Insect community analyses comparing GM and non-GM litter showed no significant differences, and the two GM litters showed differences only in the 84-day litterbags. The total abundance and species richness of insects were also similar on GM and non-GM litter. The results presented here suggest that genetic modifications in trees can influence litter quality and thus have a potential to generate effects that can cross ecosystem boundaries and influence ecosystem processes not directly associated with the tree. Overall, the realized ecological effects of the GM tree varieties used here were nevertheless shown to be relatively small.

  • 64. Axelsson, Sara
    et al.
    Eriksson, Kåre
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Nilsson, Ulrika
    Determination of resin acids during production of wood pellets-a comparison of HPLC/ESI-MS with the GC/FID MDHS 83/2 method2011In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 13, no 10, p. 2940-2945Article in journal (Refereed)
    Abstract [en]

    Resin acids are constituents of natural and technical products of widespread use. Exposure is known to cause health effects in the airways and on the skin. Liquid chromatography/positive ion electrospray-mass spectrometry (HPLC/pos ESI-MS) was investigated for determination of 7-oxodehydroabietic (7-OXO), dehydroabietic (DHAA) and abietic acid (AA) in wood dust-containing air samples as a derivatisation-free alternative to the GC/FID HSE method 83/2, developed by the Health and Safety Executive UK. The resin acid 7-OXO was measured as a marker for oxidised resin acids, which are known to be the main contact allergens in colophonium. The found detection limits were 0.42 ng m(-3) for 7-OXO, 5.2 ng m(-3) for DHAA and 9.4 ng m(-3) for AA, respectively, which are considerably lower than with the GC/FID method (24, 115 and 89 ng m(-3)). The two methods correlated well, although consistently and significantly lower concentrations of 7-OXO were detected with LC/MS. The higher concentration of this compound with MDHS 83/2 is suggested to be an artefact from the derivatisation step in the presence of soluble wood dust remains.

  • 65.
    B. Krishnamurthy, Chandra Kiran
    Umeå University, Faculty of Social Sciences, Center for Environmental and Resource Economics (CERE). Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Economics. The Beijer Institute of Ecological Economics, The Royal Swedish Academy of Sciences.
    Optimal management of groundwater under uncertainty: a unified approach2017In: Environmental and Resource Economics, ISSN 0924-6460, E-ISSN 1573-1502, Vol. 67, no 2, p. 351-377Article in journal (Refereed)
    Abstract [en]

    Discrete-time stochastic models of management of groundwater resources have been extensively used for understanding a number of issues in groundwater management. Most models used suffer from two drawbacks: relatively simplistic treatment of the cost of water extraction, and a lack of important structural results (such as monotonicity of extraction in stock and concavity of the value function), even in simple models. Lack of structural properties impede both practical policy simulation and clarity of understanding of the resulting models and the underlying economics. This paper provides a unifying framework for these models in two directions; first, the usual cost function is extended to encompass cases where marginal cost of pumping depends on the stock and second, the analysis dispenses with assumptions of concavity of the objective function and compactness of the state space, using instead lattice-theoretic methods. With these modifications, a comprehensive investigation of which structural properties can be proved in each of the resulting cases is carried out. It is shown that for some of the richer models more structural properties may be proved than for the simpler model used in the literature. This paper also introduces to the resource economics literature an important method of proving convergence to a stationary distribution which does not require monotonicity in stock of resource. This method is of interest in a variety of renewable resource model settings.

  • 66.
    B. Krishnamurthy, Chandra Kiran
    et al.
    Umeå University, Faculty of Social Sciences, Center for Environmental and Resource Economics (CERE). Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Economics.
    Cioffi, Francesco
    University of Rome ‘La Sapienza’, Italy.
    Lall, Upmanu
    Columbia University, New York.
    Rus, Ester
    Thames Water Innovation Centre, Reading, UK.
    Space-time Structure of Extreme Precipitation in Europe over the last CenturyArticle in journal (Refereed)
  • 67.
    Backlund, Kenneth
    Umeå University, Faculty of Social Sciences, Department of Economics.
    Nuclear power policy as a differential game2000Report (Other academic)
    Abstract [en]

    This paper examines nuclear energy output in a differential game framework involving two countries. The countries differ regarding nuclear technology with one being relatively safe and the other less safe. Simulation of a numerical model gives the following results, (i) A cooperative agreement will imply less use of nuclear energy compared with both a noncooperative Nash equilibrium and an uncontrolled market solution, (ii) The country with relatively safe nuclear energy technology benefits most from a cooperative solution, (iii) Starting from an uncontrolled market economy, an agreement between the countries to introduce taxation of nuclear energy will be beneficial for both countries. However, by starting from the noncooperative Nash equilibrium, an agreement to slightly increase the nuclear energy taxes will be most beneficial for the country with less safe nuclear energy technology.

  • 68.
    Backlund, Kenneth
    Umeå University, Faculty of Social Sciences, Department of Economics.
    On the role of green taxes in social accounting: a numerical analysis2000Report (Other academic)
    Abstract [en]

    This paper addresses social accounting numerically in a dynamic general equilibrium model. The main purposes are to study: (i) whether emission taxes based on static willingness to pay information can be used to improve the welfare level, and; (ii) whether these taxes provide close enough approximations of the correct Pigou-vian emission tax to be useful in the context of social accounting. The results indicate that, if environmental quality is relatively linear with respect to pollution, the approximation of the Pigouvian emission tax will bring the economy close to the socially optimal solution and, at the same time, provide a close approximation of the value of net investments in environmental capital.

  • 69.
    Backlund, Kenneth
    Umeå University, Faculty of Social Sciences, Department of Economics.
    Welfare measurement, externalities and Pigouvian taxation in dynamic economies2000Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of five papers.

    Paper [1] analyzes one possible way of replacing dynamic Pigouvian taxes by a static approximation of such taxes from the point of view of social accounting. The idea is to approximate a Pigouvian emission tax by using the instantaneous marginal willingness to pay to reduce the stock of pollution. If this approximation is close enough to the correct Pigouvian tax it will be useful for at least two reasons: (i) it brings the economy close to the socially optimal solution; and (ii) it provides information relevant for social accounting by closely approximating the value of additions to the stock of pollution.

    Paper [2] analyzes the welfare effects of an agreement between countries to slightly increase their emission taxes. The results indicate that such an agreement need not necessarily increase the global welfare level, even if each individual country has set its prereform emission tax to be lower than the marginal social cost of pollution.

    Paper [3] provides an economic framework for analyzing the global warming problem, emphasizing the use of forests as a means of carbon sequestration. We explore the difference between the decentralized economy and the socially optimal resource allocation, and discuss the appropriate tax system required to implement the first best optimum.

    Paper [4] incorporates the uncertainty involved in the production of nuclear energy into a dynamic general equilibrium growth model. We compare the resource allocation in the decentralized economy with the socially optimal resource allocation and design the dynamic Pigouvian taxes that make the decentralized economy reproduce the socially optimal resource allocation.

    Paper [5] treats externalities from nuclear power in a dynamic differential game framework involving two countries, which differ with regard to their nuclear technology. The model is solved numerically, where one country is considered relatively safe and the other relatively less safe.

  • 70.
    Backlund, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Återvinning av dryckeskartonger: En studie som syftar till att öka återvinningsgraden av Tetra Paks förpackningar i Indonesien2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    People of the modern world consume more than they ever used to do. Because of the close correlation between consumption and the amount of waste, the waste volume is also expected to increase. The purpose of this study is to examine if some measures in the recycling process from Sweden could be implemented in Indonesia. In fact, Indonesia is one of the countries in which the waste management system is struggling. Tetra Pak, one of the world leading producer of food packaging, is studied in this report. Tetra Paks recycling rate of their beverage cartons is relatively low, 8.42 %, in Indonesia compared with their recycling rate in other countries. To answer the purpose, information was collected from scientific reports, by interviews carried out in both Sweden and Indonesia and by study visits in Indonesia. The results of the study shows that there are measures which could be made in the recycling process to increase the recycling rate in Indonesia. School projects and deposit systems could increase the collection rate and a drumscreen and a buffertank could make the recycling process more profitable for the papermills. There is also some alternative end products which could make the whole recycling process more public visible. One of the conclusions of this study is that the paper mills should adjust their drumscreens, this to increase the fibre yield which is crucial for the recycling value. Another conclusions is that Tetra Pak should consider to initiate a recycling business by their own, in order to reduce the burden on the environment.

  • 71.
    Backman, Fredrick
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies.
    Från föhn till feu!: Esrange och den norrländska rymdverksamhetens tillkomsthistoria från sekelskiftet 1900 till 19662010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This essay is about the origin, planning and establishment of the European Space Research Organisation's (ESRO) sounding rocket base Esrange outside Kiruna in Northern Sweden. Three main questions are examined. First I show there were not just scientific and technical but also political, economical as well as military reasons to build a European rocket base. Second, I scrutinize the reasons to choose Northern Sweden as the location for the rocket base. As it turns out, the main reasons were the favourable location of Northern Sweden within the aurora oval zone, the proximity of the Kiruna Geophysical Observatory, and the possibility to use a large, although not quite uninhabited, area where the launched rockets could crash. Finally, I examine the difficulty of talking about boundaries of various kinds, such as temporal, spatial and functional. The essay also provides a discussion on possible ways to continue research on this topic.

  • 72.
    Badea, Silviu-Laurentiu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Liljelind, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Assessment of the release of organic contaminants from soil using a batch leaching test2010Conference paper (Refereed)
  • 73.
    Badea, Silviu-Laurentiu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mustafa, Majid
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Leachability and desorption of PCBs from soil and their dependency on pH and dissolved organic matter2014In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 499, p. 220-227Article in journal (Refereed)
    Abstract [en]

    pH affects both soil–water partitioning coefficient (Kd) of polychlorinated biphenyls (PCBs) and dissolved organic matter (DOM), thereby influencing PCBs' leachability from contaminated soils. To explore these incompletely understood interactions, the leachability of 11 selected PCBs in a naturally aged soil was investigated in pH static leaching tests spanning a wide pH range (2 to 9). The Kd was calculated for each of the PCBs, based on their observed concentrations in the soil and leachates obtained from each test. The concentration and composition of DOM in each leachate were also determined, the latter using FTIR spectroscopy. Correlations between the DOM's FTIR spectra and Kd values were investigated by orthogonal projections to latent structures. The log Kd-values varied among the PCB congeners and were most variable at low pH, but the values for all studied congeners decreased with increasing pH, by up to 3 log units (for PCB 187). In the pH 5–7 interval, an abrupt decrease in log Kd values with increases in pH was observed, although the total organic carbon content remained relatively stable. The FTIR data indicate that fulvic and humic acids in DOM partially deprotonate as the pH rises from 5 to 7.

  • 74. Bader, A.
    et al.
    Wieser, G. Stenberg
    Andre, M.
    Wieser, M.
    Futaana, Y.
    Persson, M.
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Nilsson, H.
    Zhang, T. L.
    Proton Temperature Anisotropies in the Plasma Environment of Venus2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 5, p. 3312-3330Article in journal (Refereed)
    Abstract [en]

    Velocity distribution functions (VDFs) are a key to understanding the interplay between particles and waves in a plasma. Any deviation from an isotropic Maxwellian distribution may be unstable and result in wave generation. Using data from the ion mass spectrometer IMA (Ion Mass Analyzer) and the magnetometer (MAG) onboard Venus Express, we study proton distributions in the plasma environment of Venus. We focus on the temperature anisotropy, that is, the ratio between the proton temperature perpendicular (T-perpendicular to) and parallel (T-parallel to) to the background magnetic field. We calculate average values of T-perpendicular to and T-parallel to for different spatial areas around Venus. In addition we present spatial maps of the average of the two temperatures and of their average ratio. Our results show that the proton distributions in the solar wind are quite isotropic, while at the bow shock stronger perpendicular than parallel heating makes the downstream VDFs slightly anisotropic (T-perpendicular to/T-parallel to > 1) and possibly unstable to generation of proton cyclotron waves or mirror mode waves. Both wave modes have previously been observed in Venus's magnetosheath. The perpendicular heating is strongest in the near-subsolar magnetosheath (T-perpendicular to/ T-parallel to approximate to 3/2), which is also where mirror mode waves are most frequently observed. We believe that the mirror mode waves observed here are indeed generated by the anisotropy. In the magnetotail we observe planetary protons with largely isotropic VDFs, originating from Venus's ionosphere.

  • 75.
    Baker, Susan
    et al.
    Cardiff University, Cardiff, Wales U.K..
    Eckerberg, Katarina
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Ecological restoration success: a policy analysis understanding2016In: Restoration Ecology, ISSN 1061-2971, E-ISSN 1526-100X, Vol. 24, no 3, p. 284-290Article in journal (Refereed)
    Abstract [en]

    This article discusses how ecological restoration success can be understood and evaluated using a policy analysis lens. First, this article details a conceptual tool that helps to develop a more encompassing set of criteria to assess restoration activities that provide socioeconomic benefits. Second, by broadening the understanding of restoration success and how it can be evaluated, it allows a more critical view of evaluation itself and its uses as a policy tool. A table is presented that can help practitioners reveal preferences and clarify the aims and objectives of particular initiatives. The table also sensitizes practitioners to the complexity of the links between restoration rationales and evaluation criteria, which in turn may open up much needed discussion and dialogue between restoration participants about the underlying values an actor may wish to promote. It heightens awareness of the fact that evaluation methods need to recognize that restoration is driven by multiple rationales often in the same project, both process driven and output oriented, which in turn can change over time. Adding process and output criteria together may also raise issues of priority. Evaluation criteria thus need to be assigned in ways that reflect these multiplicities, while at the same time recognizing that some restoration values might be conflictual and that there may be winners and losers. Furthermore, judgement about "failure" of a project can change as new goals emerge in delivery and implementation. Ecological restoration evaluation should therefore be ongoing, contextual, and not a one-off event.

  • 76.
    Baker, Susan
    et al.
    Cardiff School of Social Sciences, Cardiff University, Wales, UK.
    Eckerberg, Katarina
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Zachrisson, Anna
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Political science and ecological restoration2014In: Environmental Politics, ISSN 0964-4016, E-ISSN 1743-8934, Vol. 23, no 3, p. 509-524Article in journal (Refereed)
    Abstract [en]

    Ecological restoration has taken on a new significance in the face of climate change and biodiversity loss. Despite its growing policy salience, however, the social and political sciences have paid limited attention to the study of ecological restoration policy and practice. By drawing upon the political science study of multilevel governance, institutions, power elations, and place-based politics, a flavour is given of what a political science engagement might contribute to the rich tapestry of analysis that has already been produced by other disciplines on ecological restoration. As the use of restoration grows, it is increasingly likely that it will give rise to social dispute and be brought into conflict with a variety of environmental, cultural, economic, and community interests. Restoration policy and projects encounter professional and institutional norms as well as place-specific interests and values. There is urgent need to investigate how and in what ways some interests become winners and others losers in these activities, and how this in turn can influence ecological restoration outcomes. A political science lens could help build new criteria for evaluating the success of ecological restoration, ones that combine both process- and product-driven considerations.

  • 77. Balint, Miklos
    et al.
    Pfenninger, Markus
    Grossart, Hans-Peter
    Taberlet, Pierre
    Vellend, Mark
    Leibold, Mathew A.
    Englund, Göran
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bowler, Diana
    Environmental DNA time series in ecology2018In: Trends in Ecology & Evolution, ISSN 0169-5347, E-ISSN 1872-8383, Vol. 33, no 12, p. 945-957Article, review/survey (Refereed)
    Abstract [en]

    Ecological communities change in time and space, but long-term dynamics at the century-to-millennia scale are poorly documented due to lack of relevant data sets. Nevertheless, understanding long-term dynamics is important for explaining present-day biodiversity patterns and placing conservation goals in a historical context. Here, we use recent examples and new perspectives to highlight how environmental DNA (eDNA) is starting to provide a powerful new source of temporal data for research questions that have so far been overlooked, by helping to resolve the ecological dynamics of populations, communities, and ecosystems over hundreds to thousands of years. We give examples of hypotheses that may be addressed by temporal eDNA biodiversity data, discuss possible research directions, and outline related challenges.

  • 78. Balk, Berth M.
    et al.
    Brännlund, Runar
    Umeå University, Faculty of Social Sciences, Department of Economics. SLU.
    Färe, Rolf
    Grosskopf, Shwana
    Lindmark, Magnus
    Umeå University, Faculty of Social Sciences, Department of Economic History.
    Environmental Performance in Swedish Manufacturing 1913-19902006In: The theory and practice of environmental and resource economics: essays in honour of Karl-Gustaf Löfgren / [ed] Thomas Aronsson, Roger Axelsson, Runar Brännlund, Cheltenham: Edward Elgar , 2006, p. 287-306Chapter in book (Refereed)
  • 79.
    Bandau, Franziska
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Albrectsen, Benedicte Riber
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Julkunen-Tiitto, Riitta
    Gundale, Michael J.
    Genotypic variability in Populus tremula L. affects how anthropogenic nitrogen enrichment influences litter decomposition2017In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 410, no 1-2, p. 467-481Article in journal (Refereed)
    Abstract [en]

    Boreal forests can receive substantial nitrogen (N) enrichment via atmospheric N deposition and industrial forest fertilization. While it is known that N enrichment can impact ecosystem properties, such as litter decomposition, it remains poorly understood how genetic variability within plant species modifies these impacts. We grew replicates of ten Populus tremula L. genotypes (GTs) under 3 N conditions; ambient, and levels representing atmospheric N deposition and industrial forest fertilization. We measured leaf and litter physical and chemical traits, and conducted a litter decomposition assay. Leaf traits varied due to N treatment, GT, and constitutive tannin levels. Leaf traits were in some cases correlated with litter traits, and decomposition was influenced by single and interactive effects of N and GT. Nitrogen addition unexpectedly decelerated decomposition, potentially due to changes in specific leaf area (SLA). Variation in decomposition rates among the GTs was best explained by their differences in SLA, and lignin:N ratio. Nitrogen addition also caused a shift in which traits most strongly influenced decomposition. Our findings highlight that the considerable diversity present in tree species can have a strong influence on ecosystem processes, such as decomposition, and how these processes respond to environmental change.

  • 80.
    Barabash, Victoria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kirkwood, S.
    Feofilov, A.
    Kutepov, A.
    Polar Mesosphere Summer Echoes during the July 2000 Solar Proton Event2004In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, p. 759-771Article in journal (Refereed)
    Abstract [en]

    The influence of the solar proton event (SPE) 14–16 July 2000 on Polar Mesosphere Summer Echoes (PMSE) is examined. PMSE were observed by the Esrange VHF MST Radar (ESRAD) at 67°53'N, 21°06'E. The 30MHz Imaging Riometer for Ionospheric Studies IRIS in Kilpisjärvi (69°30'N, 20°47'E) registered cosmic radio noise absorption caused by ionisation changes in response to the energetic particle precipitation. An energy deposition/ion-chemical model was used to estimate the density of free electrons and ions in the upper atmosphere. Particle collision frequencies were calculated from the MSISE-90 model. Electric fields were calculated using conductivities from the model and measured magnetic disturbances. The electric field reached a maximum of 91mV/m during the most intensive period of the geomagnetic storm accompanying the SPE. The temperature increase due to Joule and particle heating was calculated, taking into account radiative cooling. The temperature increase at PMSE heights was found to be very small.

    The observed PMSE were rather intensive and extended over the 80–90km height interval. PMSE almost disappeared above 86km at the time of greatest Joule heating on 15 July 2000. Neither ionisation changes, nor Joule/particle heating can explain the PMSE reduction. Transport effects due to the strong electric field are a more likely explanation.

  • 81. Barrio, I. C.
    et al.
    Bueno, C. G.
    Gartzia, M.
    Soininen, E. M.
    Christie, K. S.
    Speed, J. D. M.
    Ravolainen, V. T.
    Forbes, B. C.
    Gauthier, G.
    Horstkotte, Tim
    Hoset, K. S.
    Høye, T. T.
    Jónsdóttir, I. S.
    Lévesque, E.
    Mörsdorf, M. A.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wookey, P. A.
    Hik, D. S.
    Biotic interactions mediate patterns of herbivore diversity in the Arctic2016In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 25, no 9, p. 1108-1118Article in journal (Refereed)
    Abstract [en]

    Aim: Understanding the forces shaping biodiversity patterns, particularly for groups of organisms with key functional roles, will help predict the responses of ecosystems to environmental changes. Our aim was to evaluate the relative role of different drivers in shaping the diversity patterns of vertebrate herbivores, a group of organisms exerting a strong trophic influence in terrestrial Arctic ecosystems. This biome, traditionally perceived as homogeneous and low in biodiversity, includes wide variation in biotic and physical conditions and is currently undergoing major environmental change. Location: The Arctic (including the High Arctic, Low Arctic and Subarctic) MethodsWe compiled available data on vertebrate (birds and mammals) herbivore distribution at a pan-Arctic scale, and used eight variables that represent the most relevant hypotheses for explaining patterns of species richness. We used range maps rasterized on a 100kmx100km equal-area grid to analyse richness patterns of all vertebrate herbivore species combined, and birds and mammalian herbivores separately. Results: Overall, patterns of herbivore species richness in the Arctic were positively related to plant productivity (measured using the normalized difference vegetation index) and to the species richness of predators. Greater species richness of herbivores was also linked to areas with a higher mean annual temperature. Species richness of avian and mammalian herbivores were related to the distance from the coast, with the highest avian richness in coastal areas and mammalian richness peaking further inland. Main conclusions: Herbivore richness in the Arctic is most strongly linked to primary productivity and the species richness of predators. Our results suggest that biotic interactions, with either higher or lower trophic levels or both, can drive patterns of species richness at a biome-wide scale. Rapid ongoing environmental changes in the Arctic are likely to affect herbivore diversity through impacts on both primary productivity and changes in predator communities via range expansion of predators from lower latitudes.

  • 82. Barrio, Isabel C.
    et al.
    Lindén, Elin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Te Beest, Mariska
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rocha, Adrian
    Soininen, Eeva M.
    Alatalo, Juha M.
    Andersson, Tommi
    Asmus, Ashley
    Boike, Julia
    Bråthen, Kari Anne
    Bryant, John P.
    Buchwal, Agata
    Bueno, C. Guillermo
    Christie, Katherine S.
    Denisova, Yulia V.
    Egelkraut, Dagmar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ehrich, Dorothee
    Fishback, LeeAnn
    Forbes, Bruce C.
    Gartzia, Maite
    Grogan, Paul
    Hallinger, Martin
    Heijmans, Monique M. P. D.
    Hik, David S.
    Hofgaard, Annika
    Holmgren, Milena
    Høye, Toke T.
    Huebner, Diane C.
    Jónsdóttir, Ingibjorg Svala
    Kaarlejärvi, Elina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
    Kumpula, Timo
    Lange, Cynthia Y. M. J. G.
    Lange, Jelena
    Lévesque, Esther
    Limpens, Juul
    Macias-Fauria, Marc
    Myers-Smith, Isla
    van Nieukerken, Erik J.
    Normand, Signe
    Post, Eric S.
    Schmidt, Niels Martin
    Sitters, Judith
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
    Skoracka, Anna
    Sokolov, Alexander
    Sokolova, Natalya
    Speed, James D. M.
    Street, Lorna E.
    Sundqvist, Maja K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. The Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen, Copenhagen Ø, Denmark.
    Suominen, Otso
    Tananaev, Nikita
    Tremblay, Jean-Pierre
    Urbanowicz, Christine
    Uvarov, Sergey A.
    Watts, David
    Wilmking, Martin
    Wookey, Philip A.
    Zimmermann, Heike H.
    Zverev, Vitali
    Kozlov, Mikhail V.
    Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome2017In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 40, no 11, p. 2265-2278Article in journal (Refereed)
    Abstract [en]

    Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6-7% over the current levels with a 1 degrees C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems.

  • 83.
    Bartels, Pia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Allochthonous Organic Matter Supports Benthic but Not Pelagic Food Webs in Shallow Coastal Ecosystems2018In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, no 7, p. 1459-1470Article in journal (Refereed)
    Abstract [en]

    Rivers transport large amounts of allochthonous organic matter (OM) to the ocean every year, but there are still fundamental gaps in how allochthonous OM is processed in the marine environment. Here, we estimated the relative contribution of allochthonous OM (allochthony) to the biomass of benthic and pelagic consumers in a shallow coastal ecosystem in the northern Baltic Sea. We used deuterium as a tracer of allochthony and assessed both temporal variation (monthly from May to August) and spatial variation (within and outside river plume). We found variability in allochthony in space and time and across species, with overall higher values for zoobenthos (26.2 +/- 20.9%) than for zooplankton (0.8 +/- 0.3%). Zooplankton allochthony was highest in May and very low during the other months, likely as a result of high inputs of allochthonous OM during the spring flood that fueled the pelagic food chain for a short period. In contrast, zoobenthos allochthony was only lower in June and remained high during the other months. Allochthony of zoobenthos was generally higher close to the river mouth than outside of the river plume, whereas it did not vary spatially for zooplankton. Last, zoobenthos allochthony was higher in deeper than in shallower areas, indicating that allochthonous OM might be more important when autochthonous resources are limited. Our results suggest that climate change predictions of increasing inputs of allochthonous OM to coastal ecosystems may affect basal energy sources supporting coastal food webs.

  • 84. Bartels, Pia
    et al.
    Cucherousset, Julien
    Gudasz, Cristian
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Premke, Katrin
    Rubach, Anja
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Steger, Kristin
    Tranvik, Lars J.
    Eklov, Peter
    Terrestrial subsidies to lake food webs: an experimental approach2012In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 168, no 3, p. 807-818Article in journal (Refereed)
    Abstract [en]

    Cross-ecosystem movements of material and energy are ubiquitous. Aquatic ecosystems typically receive material that also includes organic matter from the surrounding catchment. Terrestrial-derived (allochthonous) organic matter can enter aquatic ecosystems in dissolved or particulate form. Several studies have highlighted the importance of dissolved organic carbon to aquatic consumers, but less is known about allochthonous particulate organic carbon (POC). Similarly, most studies showing the effects of allochthonous organic carbon (OC) on aquatic consumers have investigated pelagic habitats; the effects of allochthonous OC on benthic communities are less well studied. Allochthonous inputs might further decrease primary production through light reduction, thereby potentially affecting autotrophic resource availability to consumers. Here, an enclosure experiment was carried out to test the importance of POC input and light availability on the resource use in a benthic food web of a clear-water lake. Corn starch (a C-4 plant) was used as a POC source due to its insoluble nature and its distinct carbon stable isotope value (delta C-13). The starch carbon was closely dispersed over the bottom of the enclosures to study the fate of a POC source exclusively available to sediment biota. The addition of starch carbon resulted in a clear shift in the isotopic signature of surface-dwelling herbivorous and predatory invertebrates. Although the starch carbon was added solely to the sediment surface, the carbon originating from the starch reached zooplankton. We suggest that allochthonous POC can subsidize benthic food webs directly and can be further transferred to pelagic systems, thereby highlighting the importance of benthic pathways for pelagic habitats.

  • 85.
    Bartels, Pia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Cucherousset, Julien
    Steger, Kristin
    Eklöv, Peter
    Tranvik, Lars J
    Hillebrand, Helmut
    Reciprocal subsidies between freshwater and terrestrial ecosystems structure consumer resource dynamics2012In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 93, no 5, p. 1173-1182Article in journal (Refereed)
    Abstract [en]

    Cross-ecosystem movements of material and energy, particularly reciprocal resource fluxes across the freshwater-land interface, have received major attention. Freshwater ecosystems may receive higher amounts of subsidies (i.e., resources produced outside the focal ecosystem) than terrestrial ecosystems, potentially leading to increased secondary production in freshwaters. Here we used a meta-analytic approach to quantify the magnitude and direction of subsidy inputs across the freshwater-land interface and to determine subsequent responses in recipient animals. Terrestrial and freshwater ecosystems differed in the magnitude of subsidies they received, with aquatic ecosystems generally receiving higher subsidies than terrestrial ecosystems. Surprisingly, and despite the large discrepancy in magnitude, the contribution of these subsidies to animal carbon inferred from stable isotope composition did not differ between freshwater and terrestrial ecosystems, likely due to the differences in subsidy quality. The contribution of allochthonous subsidies was highest to primary consumers and predators, suggesting that bottom-up and top-down effects may be affected considerably by the input of allochthonous resources. Future work on subsidies will profit from a food web dynamic approach including indirect trophic interactions and propagating effects.

  • 86.
    Bartels, Pia
    et al.
    Department of Ecology and Genetics, Limnology, Uppsala University, Uppsala, Sweden.
    Hirsch, Philipp E.
    Svanbäck, Richard
    Eklöv, Peter
    Water Transparency Drives Intra-Population Divergence in Eurasian Perch (Perca fluviatilis)2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 8, p. e43641-Article in journal (Refereed)
    Abstract [en]

    Trait combinations that lead to a higher efficiency in resource utilization are important drivers of divergent natural selection and adaptive radiation. However, variation in environmental features might constrain foraging in complex ways and therefore impede the exploitation of critical resources. We tested the effect of water transparency on intra-population divergence in morphology of Eurasian perch (Perca fluviatilis) across seven lakes in central Sweden. Morphological divergence between near-shore littoral and open-water pelagic perch substantially increased with increasing water transparency. Reliance on littoral resources increased strongly with increasing water transparency in littoral populations, whereas littoral reliance was not affected by water transparency in pelagic populations. Despite the similar reliance on pelagic resources in pelagic populations along the water transparency gradient, the utilization of particular pelagic prey items differed with variation in water transparency in pelagic populations. Pelagic perch utilized cladocerans in lakes with high water transparency and copepods in lakes with low water transparency. We suggest that under impaired visual conditions low utilization of littoral resources by littoral perch and utilization of evasive copepods by pelagic perch may lead to changes in morphology. Our findings indicate that visual conditions can affect population divergence in predator populations through their effects on resource utilization.

  • 87.
    Barthelemy, Helene
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stark, Sari
    Rovaniemi, Finland.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Strong Responses of Subarctic Plant Communities to Long-Term Reindeer Feces Manipulation2015In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 18, no 5, p. 740-751Article in journal (Refereed)
    Abstract [en]

    Deposition of feces is a key mechanism by which herbivores influence soil nutrient cycling and plant production, but the knowledge about its importance for plant production and community structure is still rudimental since experimental evidence is scarce. We thus performed a 7-year long reindeer feces manipulation experiment in two tundra vegetation types with contrasting nutrient availability and analyzed effects on plant community composition and soil nutrient availability. Despite feces being fairly nutrient poor, feces manipulation had strong effect on both the nutrient-poor heath and the nutrient-rich meadow. The strongest effect was detected when feces were added at high density, with a substantial increase in total vascular plant productivity and graminoids in the two communities. Doubling natural deposition of reindeer feces enhanced primary production and the growth of deciduous shrubs in the heath. By contrast, removal of feces decreased only the production of graminoids and deciduous shrubs in the heath. Although the response to feces addition was faster in the nutrient-rich meadow, after 7 years it was more pronounced in the nutrient-poor heath. The effect of feces manipulation on soil nutrient availability was low and temporarily variable. Our study provides experimental evidence for a central role of herbivore feces in regulating primary production when herbivores are abundant enough. Deposition of feces alone does, however, not cause dramatic vegetation shifts; to drive unproductive heath to a productive grass dominated state, herbivore trampling, and grazing are probably also needed.

  • 88.
    Barthelemy, Hélène
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stark, Sari
    Michelsen, Anders
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Urine is an important nitrogen source for plants irrespective of vegetation composition in an Arctic tundra: Insights from a N-15-enriched urea tracer experiment2018In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 106, no 1, p. 367-378Article in journal (Refereed)
    Abstract [en]

    1. Mammalian herbivores can strongly influence nitrogen (N) cycling and herbivore urine could be a central component of the N cycle in grazed ecosystems. Despite its potential role for ecosystem productivity and functioning, the fate of N derived from urine has rarely been investigated in grazed ecosystems. 2. This study explored the fate of N-15-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer for more than 50years. We followed the fate of the N-15 applied to the plant canopy, at 2weeks and 1year after tracer addition, in the different ecosystem N pools. 3. N-15-urea was rapidly incorporated in cryptogams and in above-ground parts of vascular plants, while the soil microbial pool and plant roots sequestered only a marginal proportion. Furthermore, the litter layer constituted a large sink for the N-15-urea, at least in the short term, indicating a high biological activity in the litter layer and high immobilization in the first phases of organic matter decomposition. 4. Mosses and lichens still constituted the largest sink for the N-15-urea 1year after tracer addition at both levels of grazing intensity demonstrating their large ability to capture and retain N from urine. Despite large fundamental differences in their traits, deciduous and evergreen shrubs were just as efficient as graminoids in taking up the N-15-urea. The total recovery of N-15-urea was lower in the intensively grazed sites, suggesting that reindeer reduce ecosystem N retention. 5. Synthesis. The rapid incorporation of the applied N-15-urea indicates that arctic plants can take advantage of a pulse of incoming N from urine. In addition, N-15 values of all taxa in the heavily grazed sites converged towards the N-15 values for urine, bringing further evidence that urine is an important N source for plants in grazed tundra ecosystems.

  • 89. Battarbee, R.W.
    et al.
    Charles, D.F.
    Bigler, Christian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Cumming, B.F.
    Renberg, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Diatoms as indicators of surface-water acidity2010In: The Diatoms: Applications for the Environmental and Earth Sciences / [ed] Smol, J. P. & Stoermer, E. F., Cambridge: Cambridge University Press, 2010, 2., p. 98-121Chapter in book (Refereed)
    Abstract [en]

    Lake acidification became an environmental issue of international significance in the late 1960s and early 1970s when Scandinavian scientists claimed that ‘acid rain’ was the principal reason why fish populations had declined dramatically in Swedish and Norwegian lakes (Odén, 1968; Jensen & Snekvik, 1972; Almer et al., 1974). Similar claims were being made at about the same time in Canada (Beamish & Harvey, 1972). However, these claims were not immediately accepted by all scientists. It was argued instead that acidification was due to natural factors or to changes in catchment land-use and management (Rosenqvist 1977, 1978; Pennington 1984; Krug & Frink, 1983).

    In the scientific debate that followed, diatom analysis played a pivotal role. It enabled the timing and extent of lake acidification to be reconstructed (Charles et al., 1989; Battarbee et al., 1990; Dixit et al., 1992a) and allowed the various competing hypotheses concerning the causes of lake acidification to be evaluated (Battarbee et al., 1985; Battarbee & Charles 1994; Emmett et al., 1994). However, diatoms had been recognized and used as indicators of water pH well before the beginning of this controversy. The ‘acid rain’ issue served to highlight the importance of diatoms and stimulated the advance of more robust and sophisticated techniques, especially the development of transfer functions for reconstructing lakewater pH and related hydrochemical variables.

    This chapter outlines the history of diatoms as pH indicators, and describes how diatoms are currently used in studies of acid and acidified waters.

  • 90.
    Batten, David F.
    et al.
    Umeå University, Faculty of Social Sciences.
    Grozev, George V.
    Managing energy futures and greenhouse gas emissions with the help of agent-based simulation2008In: Changing Stocks, Flows And Behaviors In Industrial Ecosystems / [ed] Matthias Ruth , Brynhildur Davidsdottir, Cheltenham: Edward Elgar Publishing, 2008, p. 101-121Chapter in book (Other academic)
  • 91. Bazzanti, Marcello
    et al.
    Mastrantuono, Luciana
    Pilotto, Francesca
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Depth-related response of macroinvertebrates to the reversal of eutrophication in a Mediterranean lake: Implications for ecological assessment2017In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 579, p. 456-465Article in journal (Refereed)
    Abstract [en]

    A better management of nutrient inflows into lakes has led to an improvement in their conditions (i.e. reversal of eutrophication) and the effects of this on macroinvertebrate communities that inhabit different lake-depth zones is largely unknown. This paper reports a comparison of macroinvertebrate communities living in the eulittoral, infralittoral and sublittoral/profundal zones of Lake Nemi (Central Italy) before and after its natural recovery from eutrophication following the deviation of domestic Wastewater. The infralittoral zone responded more rapidly than the other two depth-zones to the improved ecological conditions, as shown by larger differences in community composition between the two periods. In the eulittoral sand, the combined effects of hydromorphological pressures and reversal of eutrophication hindered the biotic response. In the eulittoral and infralittoral zones, typical taxa of mesotrophic waters appeared or increased their abundances after the eutrophication reversal. Benthic invertebrate response was slower in the sublittoral/profundal zone due to deoxygenation that continued to prevail in the deepest area of the lake during summer. However, both tolerant and more sensitive taxa were collected there for the first time. After the reversal of eutrophication, the percentage of molluscan + large crustaceans increased in the infralittoral zone, whereas the oligochaete/chironomid ratio decreased in both sublittoral/profundal and infralittoral zones. Functional feeding metrics (percentages of filter-feeders, collector-gatherers, miners and scrapers/grazers) differently tracked the reversal of eutrophication in the three depth-zones probably according to the effects of the-reduction of nutrients on food-web structure influencing macroinvertebrates. Biological Monitoring Working Party (BMWP) and the Average Score Per Taxon (ASPT) seemed to respond to eutrophication reversal only in the sublittoral/profundal zone, where deoxygenation plays a major role as a structuring agent of the community. Our results suggest that the effects of re-. versal of eutrophication can be better assessed by examining the response of the communities belonging to each zone individually. 

  • 92.
    Becher, Marina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Cryogenic soil processes in a changing climate2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A considerable part of the global pool of terrestrial carbon is stored in high latitude soils. In these soils, repeated cycles of freezing and thawing creates soil motion (cryoturbation) that in combination with other cryogenic disturbance processes may play a profound role in controlling the carbon balance of the arctic soil. Conditions for cryogenic soil processes are predicted to dramatically change in response to the ongoing climate warming, but little is known how these changes may affect the ability of arctic soils to accumulate carbon. In this thesis, I utilize a patterned ground system, referred to as non-sorted circles, as experimental units and quantify how cryogenic soil processes affect plant communities and carbon fluxes in arctic soils. I show that the cryoturbation has been an important mechanism for transporting carbon downwards in the studied soil over the last millennia. Interestingly, burial of organic material by cryoturbation appears to have mainly occurred during bioclimatic events occurring around A.D. 900-1250 and A.D. 1650-1950 as indicated by inferred 14C ages. Using a novel photogrammetric approach, I estimate that about 0.2-0.8 % of the carbon pool is annually subjected to a net downward transport induced by the physical motion of soil. Even though this flux seems small, it suggests that cryoturbation is an important transporter of carbon over centennial and millennial timescales and contributes to translocate organic matter to deeper soil layers where respiration proceeds at slow rates. Cryogenic processes not only affect the trajectories of the soil carbon, but also generate plant community changes in both species composition and abundance, as indicated by a conducted plant survey on non-sorted circles subjected to variable differential frost heave during the winter. Here, disturbance-tolerant plant species, such as Carex capillaris and Tofieldia pusilla, seem to be favoured by disturbance generated by the differential heave. Comparison with findings from a previous plant survey on the site conducted in the 1980s suggest that the warmer temperatures during the last decades have resulted in decreased differential heave in the studied non-sorted circles. I argue that this change in cryogenic activity has increased abundance of plants present in the 1980s. The fact that the activity and function of the non-sorted circles in Abisko are undergoing changes is further supported by their contemporary carbon dioxide (CO2) fluxes. Here, my measurements of CO2 fluxes suggest that all studied non-sorted circles act as net CO2 sources and thus that the carbon balance of the soils are in a transition state. My results highlight the complex but important relationship between cryogenic soil processes and the carbon balance of arctic soils.

  • 93.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klaminder, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The use of terrestrial photogrammetry to estimate soil motion rates in non-sorted circlesManuscript (preprint) (Other academic)
    Abstract [en]

    Soil motion induced by cryogenic processes is known for creating soil surface structures (patterned ground) and redistributing carbon within Arctic soils. Lateral and vertical soil motion created by cryogenic processes proceeds over annual to millennial time-scales and is difficult to quantify without adopting disruptive soil sampling techniques. In this study, we evaluate the use of terrestrial close range photogrammetry to calculate soil motion rates within a patterned ground system (non-sorted circles). The measured rates of lateral and vertical motion were estimated and used to infer the importance of physical soil transport for the formation of non-sorted circles as well as the trajectories of soil carbon. Soil experiencing significant vertical displacement between years covered approximately 65% of the non-sorted circles and had surface levels fluctuating between 4 and -2.1 cm. Systematic lateral motion of surface stones allowed detection of lateral motion working outwards from the centre towards the sides, at rates ranging between 0.1 and 6.3 cm yr-1. We conclude that terrestrial close range photogrammetry can be used to identify the main soil movements within non-sorted circles and that this transport is an important factor controlling the trajectories of soil carbon over centennial to millennial timescales. 

  • 94.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Measuring soil motion with terrestrial close range photogrammetry in periglacial environments2014In: EUCOP 4: Book of Abstracts / [ed] Gonçalo Vieira, Pedro Pina, Carla Mora and António Correia, University of Lisbon and the University of Évora , 2014, p. 351-351Conference paper (Other academic)
    Abstract [en]

    Cryoturbation plays an important role in the carbon cycle as it redistributes carbon deeper down in the soil where the cold temperature prevents microbial decomposition. This contribution is also included in recent models describing the long-term build up of carbon stocks in artic soils. Soil motion rate in cryoturbated soils is sparsely studied. This is because the internal factors maintaining cryoturbation will be affected by any excavation, making it impossible to remove soil samples or install pegs without changing the structure of the soil. So far, mainly the motion of soil surface markers on patterned ground has been used to infer lateral soil motion rates. However, such methods constrain the investigated area to a predetermined distribution of surface markers that may result in a loss of information regarding soil motion in other parts of the patterned ground surface.

    We present a novel method based on terrestrial close range (<5m) photogrammetry to calculate lateral and vertical soil motion across entire small-scale periglacial features, such as non-sorted circles (frost boils). Images were acquired by a 5-camera calibrated rig from at least 8 directions around a non-sorted circle. During acquisition, the rig was carried by one person in a backpack-like portable camera support system. Natural feature points were detected by SIFT and matched between images using the known epipolar geometry of the calibrated rig. The 3D coordinates of points matched between at least 3 images were calculated to create a point cloud of the surface of interest. The procedure was repeated during two consecutive years to be able to measure any net displacement of soil and calculate rates of soil motion. The technique was also applied to a peat palsa where multiple exposures where acquired of selected areas.

    The method has the potential to quantify areas of disturbance and estimate lateral and vertical soil motion in non-sorted circles. Furthermore, it should be possible to quantify peat erosion and rates of desiccation crack formations in peat palsas. This tool could provide new information about cryoturbation rates that could improve existing soil carbon models and increase our understanding about how soil carbon stocks will respond to climate change.

  • 95.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olid, Carolina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Buried soil organic inclusions in non-sorted circles fields in northern Sweden: Age and Paleoclimatic context2013In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, no 1, p. 104-111Article in journal (Refereed)
    Abstract [en]

    Although burial of surface organic soil horizons into deeper mineral soil layers helps drive the long-term buildup of carbon in arctic soils, when and why buried horizons formed as result of cryoturbation in northern Sweden remain unclear. In this study, we used C-14 and Pb-210 dating to assess when organic matter was buried within non-sorted circles fields near Abisko in northern Sweden. In addition, we used aerial photos from 1959 and 2008 to detect eventual trends in cryogenic activities during this period. We found that organic matter from former organic horizons (stratigraphically intact or partly fragmented) corresponds to three major periods: 0-100 A. D., 900-1250 A. D., and 1650-1950 A. D. The latter two periods were indicated by several dated samples, while the extent of the oldest period is more uncertainty (indicated by only one sample). The aerial photos suggest a net overgrowth by shrub vegetation of previously exposed mineral soil surfaces since 1959. This overgrowth trend was seen in most of the studied fields (92 out of 137 analyzed fields), indicating that the cryogenic activity has mainly decreased in studied non-sorted circles fields since the 1950s. This latter interpretation is also supported by the absence of buried organic layers formed during the last decades. We suggest that the organic matter was buried during the transition from longer cold periods to warmer conditions. We believe these climatic shifts could have triggered regional scale burial of soil organic matter and thus affected how these soils sequestered carbon.

  • 96.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Berglund, Louise
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Decreased cryogenic disturbance: one of the potential mechanisms behind the vegetation change in the Arctic2018In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 41, no 1, p. 101-110Article in journal (Other academic)
    Abstract [en]

    During the last few decades, the Arctic has experienced large-scale vegetation changes. Understanding the mechanisms behind this vegetation change is crucial for our ability to predict future changes. This study tested the hypothesis that decreased cryogenic disturbances cause vegetation change in patterned ground study fields (non-sorted circles) in Abisko, Sweden during the last few decades. The hypothesis was tested by surveying the composition of plant communities across a gradient in cryogenic disturbance and by reinvestigating plant communities previously surveyed in the 1980s to scrutinise how these communities changed in response to reduced cryogenic disturbance. Whereas the historical changes in species occurrence associated with decreased cryogenic disturbances were relatively consistent with the changes along the contemporary gradient of cryogenic disturbances, the species abundance revealed important transient changes highly dependent on the initial plant community composition. Our results suggest that altered cryogenic disturbances cause temporal changes in vegetation dynamics, but the net effects on vegetation communities depend on the composition of initial plant species.

  • 97.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Cryogenic disturbance and its impact on carbon fluxes in a subarctic heathland2015In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 10, no 11, article id 114006Article in journal (Refereed)
    Abstract [en]

    Differential frost heave, along with the associated cryogenic disturbance that accompanies it, is an almost universal feature of arctic landscapes that potentially influences the fate of the soil carbon (C) stored in arctic soils. In this study, we quantify how gross ecosystem photosynthesis (GEP), soil respiration (Re) and the resulting net ecosystem exchange (NEE) vary in a patterned ground system (non-sorted circles) at plot-scale and whole-patterned ground scales in response to cryogenic disturbances (differential heave and soil surface disruption). We found that: (i) all studied non-sorted circles (n=15) acted as net CO2 sources (positive NEE); (ii) GEP showed a weaker decrease than Re in response to increased cryogenic disturbance/decreased humus cover, indicating that undisturbed humus-covered sites are currently the main source of atmospheric CO2 in the studied system. Interestingly, Re fluxes normalized to C pools indicated that C is currently respired more rapidly at sites exposed to cryogenic disturbances; hence, higher NEE fluxes at less disturbed sites are likely an effect of a more slowly degrading but larger total pool that was built up in the past. Our results highlight the complex effects of cryogenic processes on the C cycle at various time scales. 

  • 98. Bejarano, Maria Dolores
    et al.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gonzales del Tanago, Marta
    Marchamalo, Miguel
    Responses of riparian trees and shrubs to flow regulationalong a boreal stream in northern Sweden2011In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 56, no 5, p. 853-866Article in journal (Refereed)
    Abstract [en]

    1. Flow dynamics is a major determinant of riparian plant communities. Therefore, flowregulation may heavily affect riparian ecosystems. Despite the large number of damsworldwide, little specific information is available on the longitudinal impacts of dams onvegetation, for example how far downstream and at what degree of regulation a dam on ariver can influence riparian woodlands.

    2. We quantified the long-term responses of riparian trees and shrubs to flow regulation byidentifying their lateral distribution and habitat conditions along a boreal river in northernSweden that has been regulated by a single dam since 1948. The regulation has reducedannual flow fluctuations, this effect being largest at the dam, downstream from which itprogressively decreases following the entrance of free-flowing tributaries.

    3. We related changes in the distribution patterns, composition, abundance and richness oftree and shrub species to the degree of regulation along the river downstream from thedam. Regulation has triggered establishment of trees and shrubs closer to the channel,making it possible to measure ecological impacts of flow regulation as differences invegetation attributes relative to the positions of tree and shrub communities establishedbefore and after regulation.

    4. Trees and shrubs had migrated towards the mid-channel along the entire study reach,but the changes were largest immediately downstream of the dam. Shrubs were mostimpacted by flow regulation in terms of lateral movement, but the effect on trees extendedfurthest downstream.

    5. The species composition of trees progressively returned to its pre-regulation state withdistance downstream, but entrance of free-flowing tributaries and variation in channelmorphology and substratum caused local deviations. Species richness after regulationincreased for trees but decreased for shrubs. The changes in species composition andrichness of trees and shrubs showed no clear downstream patterns, suggesting that otherfactors than the degree of regulation were more important in governing life form.

  • 99.
    Bejarano, Maria Dolores
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sordo-Ward, Alvaro
    Alonso, Carlos
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Characterizing effects of hydropower plants on sub-daily flow regimes2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 550, p. 186-200Article in journal (Refereed)
    Abstract [en]

    A characterization of short-term changes in river flow is essential for understanding the ecological effects of hydropower plants, which operate by turning the turbines on or off to generate electricity following variations in the market demand (i.e., hydropeaking). The goal of our study was to develop an approach for characterizing the effects of hydropower plant operations on within-day flow regimes across multiple dams and rivers. For this aim we first defined ecologically meaningful metrics that provide a full representation of the flow regime at short time scales from free-flowing rivers and rivers exposed to hydropeaking. We then defined metrics that enable quantification of the deviation of the altered short-term flow regime variables from those of the unaltered state. The approach was successfully tested in two rivers in northern Sweden, one free-flowing and another regulated by cascades of hydropower plants, which were additionally classified based on their impact on short-term flows in sites of similar management. The largest differences between study sites corresponded to metrics describing sub-daily flow magnitudes such as amplitude (i.e., difference between the highest and the lowest hourly flows) and rates (i.e., rise and fall rates of hourly flows). They were closely followed by frequency-related metrics accounting for the numbers of within-day hourly flow patterns (i.e., rises, falls and periods of stability of hourly flows). In comparison, between-site differences for the duration-related metrics were smallest. In general, hydropeaking resulted in higher within-day flow amplitudes and rates and more but shorter periods of a similar hourly flow patterns per day. The impacted flow feature and the characteristics of the impact (i.e., intensity and whether the impact increases or decreases whatever is being described by the metric) varied with season. Our approach is useful for catchment management planning, defining environmental flow targets, prioritizing river restoration or dam reoperation efforts and contributing information for relicensing hydropower dams. 

  • 100. Beldowski, Jacek
    et al.
    Klusek, Zygmunt
    Szubska, Marta
    Turja, Raisa
    Bulczak, Anna I.
    Rak, Daniel
    Brenner, Matthias
    Lang, Thomas
    Kotwicki, Lech
    Grzelak, Katarzyna
    Jakacki, Jaromir
    Fricke, Nicolai
    Ostin, Anders
    Olsson, Ulf
    Fabisiak, Jacek
    Garnaga, Galina
    Nyholm, Jenny Rattfelt
    Majewski, Piotr
    Broeg, Katja
    Soderstrom, Martin
    Vanninen, Paula
    Popiel, Stanislaw
    Nawala, Jakub
    Lehtonen, Kari
    Berglind, Rune
    Umeå University, Faculty of Science and Technology, European CBRNE Center.
    Schmidt, Beata
    Chemical Munitions Search & Assessment-An evaluation of the dumped munitions problem in the Baltic Sea2016In: Deep-sea research. Part II, Topical studies in oceanography, ISSN 0967-0645, E-ISSN 1879-0100, Vol. 128, p. 85-95Article in journal (Refereed)
    Abstract [en]

    Chemical Munitions Search & Assessment (CHEMSEA) project has performed studies on chemical weapon (CW) detection, sediment pollution and spreading as well as biological effects of chemical warfare agents (CWAs) dumped in the Baltic Sea. Results suggest that munitions containing CWAs are more scattered on the seafloor than suspected, and previously undocumented dumpsite was discovered in Gdansk Deep. Pollution of sediments with CWA degradation products was local and close to the detected objects; however the pollution range was larger than predicted with theoretical models. Bottom currents observed in the dumpsites were strong enough for sediment re-suspension, and contributed to the transport of polluted sediments. Diversity and density of the faunal communities were poor at the dumping sites in comparison to the reference area, although the direct effects of CWA on benthos organisms were difficult to determine due to hypoxic or even anoxic conditions near the bottom. Equally, the low oxygen might have affected the biological effects assessed in cod and caged blue mussels. Nonetheless, both species showed significantly elevated molecular and cellular level responses at contaminated sites compared to reference sites.

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