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  • 251. Berg, Anna
    et al.
    Östlund, Lars
    Moen, Jon
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    A century of logging and forestry in a reindeer herding area in northern Sweden2008Ingår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 256, s. 1009-1020Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Boreal forest ecosystems are generally highly sensitive to logging and other forestry activities. Thus, commercial forestry has had major effects on the forests and landscape structure in northern Sweden since the middle of the 19th Century, when it rapidly extended across the region. Lichens (which constitute up to 80% of reindeer forage in winter and early spring) have often been amongst the most severely affected ecosystem components. The overall aim of the present study was to analyze how forestry has influenced the potential supply of ground-growing lichens as winter forage for the reindeer in this region over the past ca. 100 years. For this purpose, we analysed changes in forest and stand structure in Scots pine-dominated (Pinus sylvestris L.) reindeer wintering areas in the southern part of the county Norrbotten (covering ca. 58,000 ha) using detailed historical forest inventories and management plans. We found that the amount of the forest types considered potentially good pasture (mainly middleaged and old pine forests) decreased during the first part of the 20th Century. However, the quality of grazing grounds was improved by forestry during this time mainly because selective logging made the forests more open which benefits lichen growth. During the last part of the 20th century forestry impaired the quality of grazing grounds in several ways, e.g. by clear-cutting and intensified use of various silviculturalmeasures. We conclude that ca. 30–50% of the winter grazing grounds have been lost in the study area because of intensive forest management during the last century. The spatially precise historical information about the affects of forestry on lichen pasture provided in this study can be used to direct forest management which will facilitate and promote reindeer herding in the future.

  • 252. Berg, B.
    et al.
    Kjonaas, O. J.
    Johansson, M. -B
    Erhagen, Björn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Åkerblom, S.
    Late stage pine litter decomposition: Relationship to litter N, Mn, and acid unhydrolyzable residue (AUR) concentrations and climatic factors2015Ingår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 358, s. 41-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this paper is to evaluate relationships between decomposition rates of Scots pine (Pinus sylvestris) and lodgepole pine (Pinus contorta var. contorta) needle litter in the late stage of decomposition (>30% accumulated mass loss), and the progressively changing concentrations of manganese (Mn), nitrogen (N), and acid unhydrolyzable residue (AUR), as well as mean annual temperature (MAT) and mean annual precipitation (MAP). Using available long-term decomposition studies on pine needle litter in a climate gradient in Sweden, we calculated annual mass loss and related to concentrations of Mn, N, and AUR at the start of each one-year period as well as to MAT and MAP. We investigated these relationships for (i) all data on annual mass loss combined and (ii) annual mass loss for five different decomposition categories as defined by accumulated mass loss. We found highly significant, negative, and dominant relationships between annual mass loss and N (R-2 = 0.39) and AUR (R-2 = 0.39), a slight but significant positive relationship to Mn (R-2 = 0.08) and a significant negative relationship to MAT (R-2 = 0.06). The relationships were dynamic, and changed with accumulated mass loss. The rate-dampening effect of N decreased to be a rate-enhancing effect at c. 60-80% accumulated mass loss. A similar trend was found for AUR, becoming rate-enhancing at 70-80% accumulated mass loss. For Scots pine needle litter the effect of MAT on mass loss decreased with increasing accumulated mass loss and changed to a rate-dampening effect at c. 50-70% accumulated mass loss. Mn showed a stimulating effect on mass loss rate in all categories whereas MAP showed no effect in this mainly boreal climatic gradient. The current approach indicates a method for detailed studies of rate-regulating factors for litter decomposition.

  • 253. Berg, Björn
    et al.
    Erhagen, Björn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Johansson, Maj-Britt
    Nilsson, Mats
    Stendahl, Johan
    Trum, Florence
    Vesterdal, Lars
    Manganese in the litter fall-forest floor continuum of boreal and temperate pine and spruce forest ecosystems: A review2015Ingår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 358, s. 248-260Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    We have reviewed the literature on the role of manganese (Mn) in the litter fall-to-humus subsystem. Available data gives a focus on North European coniferous forests. Manganese concentrations in pine (Pinus spp.) foliar litter are highly variable both spatially and temporally within the same litter species and for the genus Pinus we found a range from 0.03 to 3.7 mg g(-1). Concentrations were related negatively to site mean annual temperature (MAT) and annual actual evapotranspiration (AET) for pine species litter but not for that of Norway spruce (Picea abies) as a single species. Combined data for several species showed a highly significant relationship to MAT. Manganese peroxidase is an Mn-dependent enzyme, found in white-rot fungi, essential for the degradation of lignin and ligninlike compounds. The decomposition rates of lignified litter tissue (late phase) is positively related to the litter's Mn concentration. Further, the Mn concentration is positively related to the limit value for decomposition - the higher the Mn concentration the smaller the stable litter fraction. Manganese release from decomposing litter appears at least in part to be species related. Thus was release from pine needle litter significantly faster (p < 0.001) than that from the Mn-richer litter of Norway spruce. Over Northern Europe concentrations of total Mn in mor humus as well as extractable Mn in the mineral soil increase with decreasing MAT and over a climatic gradient the Mn concentrations in Norway spruce mor increase more with decreasing MAT than in a gradient with Scots pine. Higher Mn concentrations in humus appear to decrease its stability and result in a higher release of carbon dioxide (CO2) and dissolved organic carbon (DOC). We conclude that this may explain (i) the lower amount of carbon (C) in mor layers under Norway spruce as compared to Scots pine as well as the higher amount of C in mineral soil under spruce. The increase in nitrogen (N) concentration in humus, following N fertilization resulted in a decrease in that of Mn. We have found four cases - empirical - with negative interaction between Mn and N; (i) in pine foliar litter fall concentrations of Mn decrease with site MAT whereas those of N increase, (ii) in decomposing late-stage litter with N retarding and Mn stimulating decomposition, (iii) for the stable phase, limit values are related negatively to N and positively to Mn, and (iv) Mn concentrations in humus decrease with MAT whereas those of N increase. (C) 2015 Elsevier B.V. All rights reserved.

  • 254.
    Berg, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Methane tree stem flux over the course of the spring flood: Spatial and temporal effects in a boreal riparian zone2022Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Methane (CH4) tree stem-atmosphere flux is viewed as a new frontier in the global carbon cycle and may be of great importance. The effect on flux from different tree species, forest ecosystems and seasons is still uncertain. This study aims to investigate how CH4 flux from stems of spruces and birches in a boreal riparian zone in northern Sweden was affected during the spring flood. Spatial and temporal patterns were examined in combination with tree species differences. A closed stem chamber system was applied to estimate CH4 flux from 28 trees during pre-snowmelt and snowmelt conditions. A three-way ANOVA analysis and Tukey´s HSD test was applied to test for main effects and interaction effects from “Field day”, “Distance to the stream” and “Species”. The study revealed that i) there was a significant increase in stem flux over the course of the spring flood while not unequivocal, ii) spruces and birches displayed no significant difference in flux, iii) the distance to the stream had no undisputable significant effect on stem flux. However, a trend in flux variation was observed with distance to the stream. No significant interaction effects were detected. Cumulative seasonal environmental changes or natural variability might explain temporal patterns. Spatial patterns may be connected to hot spots close to the stream. Results for species and interaction effects might facilitate estimations of fluxes in forested ecosystems. Methane flux rates are affected over the course of the spring flood, but further studies are needed to determine the cause for it. 

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  • 255.
    Berg, Ivan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Effects of doc and water temperature on prey use and performance of nine-spine stickleback2021Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Climate change is causing water temperature to rise, and many lakes in the boreal zone will experience browning of waters (brownification) due to increased input of dissolved organic carbon (DOC). In fish, warming may cause resource limitation and decrease both fish size and population abundance. Many fish species display ontogenetic niche shifts during their lifetime, shifting to larger prey as they grow. Brownification may change the timing for, the benefits from or prevent individuals from displaying ontogenetic niche shifts by decreasing large prey abundance in the benthic zone or making fast-moving prey harder to see. This can cause resource limitations, suppressing growth and population growth. This study investigated the effects of increasing DOC and water temperature on ontogenetic diet shifts, size structure, and population abundance in nine-spine stickleback (Pungitius pungitius) in an experimental pond system with a warming treatment and a gradient of DOC concentration. Warming had a negative effect on population number, biomass, maximum fish size, stomach fullness, and consumption of large prey. Contrary to expected outcomes, increasing DOC input resulted in higher population, biomass, and larger maximum sized fish as DOC increased. DOC did not negatively affect ontogenetic diet shifts. In the relatively shallow enclosures, the highest DOC concentration may not have reached the threshold where the shading effect of DOC overturns the benefits of extra nutrients associated with DOC. Hence, in shallow lake ecosystems, climate change induced DOC increase may support fish production, while warming may have strong negative effects on fish population abundance and size.

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  • 256.
    Berg, Ivan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Headwaters and forestry: Effect of riparian buffers on stream physiochemical properties2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Forest management practices usually preserves riparian buffers along watercourses in order to protect stream water from physical, chemical and ecological changes caused by clear-cutting. The purpose of this thesis was to investigate whether there is a relationship between the size of the riparian buffer zone along small streams, i.e., headwaters, and a number of physical and chemical attributes of these streams. Twelve headwaters in the Västerbotten county and twelve in Jönköpings county were investigated. These headwaters had a range of buffer widths from “No buffer” (no trees left), Thin buffer” (< 5 m wide), to “Moderate buffer” (>5 m wide) and “Reference” (no harvest) streams were also included. Tested physical and chemical conditions were light in the riparian zone, air and water temperature, stream bed cover and water chemistry. Buffer width had a significant effect on reducing light levels and temperature in the riparian zone; a buffer width over 13 m on each side of the stream was needed to maintain light and air temperature as in reference conditions. Regarding water temperature, increasing sedimentation and water quality, no significant reducing effect of increasing riparian buffer width was found.

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  • 257.
    Berg, Noomi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Carbon and nutrient leaching in Betula pubescens: Intraspecific leachability pattern across an environmental gradient2023Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Leaching of carbon and nutrients from leaf material can make important contributions to ecosystems biogeochemical processes but is relatively understudied. In particular, intraspecific leachability patterns and its variability across environmental gradients could be of importance to understand local ecosystem processes. The aim of this study is to gain better understanding of intraspecific leachability patterns in Betula pubescens and how it is related to leaf traits and environmental factors. Green and brown leaf material of B. pubescens from 25 islands across a natural gradient in ecosystem fertility and productivity were put in water solution whereafter the leachates were chemically analysed. Chemical analysis of foliar element concentration was also performed. To test leachability patterns between green and brown leaves, t-tests were applied. Multiple stepwise regressions were applied to test if observed leachability patterns could be explained by plasticity in leaf traits and/or environmental changes across the islands. The results of the analyses show that green leaves leached a higher portion of elements than brown leaves, probably explained by resorptive processes during senescence. Additionally, the quantities of leached elements from the leaves probably make important contributions to the local bioavailable nutrient-pool. Additionally, some leaf traits, known to vary across the environmental gradient, were strongly related to observed leachability patterns. Despite that, no strong relations between leachability patterns and environmental factors were found. To gain deeper understanding of the direct and indirect drivers of intraspecific leachability patterns, structural modelling would be of interest. 

  • 258.
    Bergdahl, Annika
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Hur hälsan hos butiksmedarbetare påverkats av covid-19-pandemin2021Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The covid-19 pandemic can endanger the physical and mental health of people in general, but a particularly vulnerable group are people who work in stores. The purpose of the study was to examine how the health of store employees had been affected by the covid-19 pandemic and to identify if age, gender, form of employment, line of business and type of store, are important contributing factors. To answer the purpose a web-based survey was performed where 783 store employees participated. The results showed that store employees had relatively high anxiety levels concerning covid-19 infection and relatively high stress levels concerning increased workload because of covid-19. A large proportion of the store employees who had less social interactions due to their job had experienced sadness. The results also showed that there were several factors that affected the health of store employees. The factors who clearly influenced the anxiety and stress levels were if the store employees had shown symptoms, has had covid-19 or were in risk group. Gender, line of business and what type of store they worked in also had some impact on anxiety or stress levels. Age and form of employment were however factors who influenced the health very little according to this study, but to draw this conclusion with certainty further studies are needed. The conclusion is that the health of store employees has been negatively affected by the covid-19 pandemic regarding increased anxiety, stress and sadness, and also that risk group is the foremost contributing factor.

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  • 259.
    Bergdahl, Lisa
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Miljöklassning av flerbostadshus: Laboratorvägen 7 och 9 i Umeå2009Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 260. Berger, R
    et al.
    Bergström, L
    Granéli, E
    Kautsky, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    How does eutrophication affect different life stages of Fucus vesiculosus in the Baltic Sea? - a conceptual model2004Ingår i: Biology of the Baltic Sea, 2004, s. 243-248Kapitel i bok, del av antologi (Refereegranskat)
  • 261. Berger, S. A.
    et al.
    Diehl, S.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Kunz, T. J.
    Albrecht, D.
    Oucible, A. M.
    Ritzer, S.
    Light supply, plankton biomass, and seston stoichiometry in a gradient of lake mixing depths2006Ingår i: Limnology and Oceanography, Vol. 51, nr 4, s. 1898-1905Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We derive from a dynamic model that light availability, phytoplankton density, and the carbon : nutrient ratio of phytoplankton biomass should all be negatively related to mixed surface layer depth, whereas the areal standing stock of phytoplankton should show a unimodal, and total and dissolved nutrients a horizontal or increasing, relationship to mixing depth. These predictions agree closely with data from 65 central European lakes during summer stratification. In addition, zooplankton biomass was strongly negatively related to mixing depth in a subset of lakes. A decrease in mixing depth is thus a form of enrichment with light of the mixed surface layer, the effects of which could propagate to higher trophic levels.

  • 262. Berger, S. A.
    et al.
    Diehl, S.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Stibor, H.
    Trommer, G.
    Ruhenstroth, M.
    Wild, A.
    Weigert, A.
    Jager, C. G.
    Striebel, M.
    Water temperature and mixing depth affect timing and magnitude of events during spring succession of the plankton2007Ingår i: Oecologia, Vol. 150, nr 4, s. 643-654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In many lakes, the most conspicuous seasonal events are the phytoplankton spring bloom and the subsequent clear-water phase, a period of low-phytoplankton biomass that is frequently caused by mesozooplankton (Daphnia) grazing. In Central European lakes, the timing of the clear-water phase is linked to large-scale climatic forcing, with warmer winters being followed by an earlier onset of the clear-water phase. Mild winters may favour an early build-up of Daphnia populations, both directly through increased surface temperatures and indirectly by reducing light limitation and enhancing algal production, all being a consequence of earlier thermal stratification. We conducted a field experiment to disentangle the separate impacts of stratification depth (affecting light supply) and temperature on the magnitude and timing of successional events in the plankton. We followed the dynamics of the phytoplankton spring bloom, the clear-water phase and the spring peak in Daphnia abundance in response to our experimental manipulations. Deeper mixing delayed the timing of all spring seasonal events and reduced the magnitudes of the phytoplankton bloom and the subsequent Daphnia peak. Colder temperatures retarded the timing of the clear-water phase and the subsequent Daphnia peak, whereas the timing of the phytoplankton peak was unrelated to temperature. Most effects of mixing depth (light) and temperature manipulations were independent, effects of mixing depth being more prevalent than effects of temperature. Because mixing depth governs both the light climate and the temperature regime in the mixed surface layer, we propose that climate-driven changes in the timing and depth of water column stratification may have far-reaching consequences for plankton dynamics and should receive increased attention.

  • 263.
    Berger, Sandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Vattnet, ljuset och dess betydelse för krukväxten: Varierande känslighet hos Pelargonium x hortorum och Kalanchoe blossfeldiana2019Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Well-balanced water and light conditions are two of the most important necessities of keeping houseplants alive, although the sensitivity to these conditions varies in different kinds of plants. This report covers the effects of light and water conditions to the life of two  of our most popular houseplants Pelargonium x hortorum and Kalanchoe blossfeldiana.  Conclusions could be made by studying the two species and the responses brought on by  the following combinations of treatments; light/water, light/drought, darkness/water and darkness/drought. The purpose of the study was to gain knowledge surrounding  the treatment of houseplants, how responses differ between different species and whether or not this leads to assumptions regarding conditioning of our houseplants during periods of not being home to care for them. In conclusion darkness is the far more harmful aspect between darkness and drought, and P. x hortorum is more sensitive to adverse light conditions compared to K. blossfeldiana. In dark treatment the survival between the two species differed to the extent that P. x hortorum was left with no healthy leaves on any of the plants after just three weeks, while the K. blossfeldiana plants still had on average approximately half of its original leaves still healthy. Water conditions were a nonfactor to the time of survival in darkness in both species. In drought and light conditions on the other hand, the reduction of healthy leaves by the end of the six week experiment did not differ between the two species. It was also noted that P. x hortorum plants subjected to normal light and water treatment was strikingly more productive in producing new leaves than the K. blossfeldiana plants. During the six week experiment the P. x hortorum controls on average doubled its number of healthy leaves, while barely any growth was observed in the K. blossfeldiana controls.  

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  • 264.
    Berger, Stella A.
    et al.
    Univ Munich, Dept Biol 2, Planegg Martinsried, Germany; Univ Georgia, Skidaway Inst Oceanog, Savannah, GA USA.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Univ Munich, Dept Biol 2, Planegg Martinsried, Germany.
    Stibor, Herwig
    Univ Munich, Dept Biol 2, Planegg Martinsried, Germany.
    Sebastian, Patrizia
    Univ Munich, Dept Biol 2, Planegg Martinsried, Germany.
    Scherz, Antonia
    Univ Munich, Dept Biol 2, Planegg Martinsried, Germany.
    Separating effects of climatic drivers and biotic feedbacks on seasonal plankton dynamics: no sign of trophic mismatch2014Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 59, nr 10, s. 2204-2220Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climate change may impact most strongly on temperate lake plankton communities in spring, when light availability and water temperature change rapidly due to thermal stratification. Effects of changing light and temperature on one food-web component transfer to other components, producing a complex interplay between physical drivers and biotic feedbacks. Understanding this interplay is important, because altered climate regimes could result in phenological mismatch between the phytoplankton spring bloom and the timing of maximum food requirements of grazers. To separate direct effects of light and temperature on spring plankton dynamics from effects mediated through micro- and mesograzer feedbacks, we manipulated water temperature, stratification depth and presence/absence of the mesograzer Daphnia in lake mesocosms. In early spring, stratification depth and water temperature directly influenced the light supply to phytoplankton and the growth rates of all plankton groups. Subsequently, indirect effects, including light-dependent food supply to grazers and temperature-dependent grazing pressure, became increasingly important. Phytoplankton and Daphnia peaked earlier in warmer treatments and reached higher peaks when stratification depth was shallower. Ciliates responded positively to increased food density and higher temperature and subsequently affected the taxonomic composition, but not the total biomass, of phytoplankton. In the absence of Daphnia, phytoplankton did not enter a distinct clear water phase. When present, Daphnia caused an extended clear water phase, maintaining phytoplankton and ciliates at low levels throughout early summer and suppressing all direct effects of physical drivers on these plankton groups. Our Daphnia treatments mimicked the high and low fish predation settings of the largely descriptive, recently revised Plankton Ecology Group (PEG) model of seasonal plankton succession and explored their responses to climate change scenarios. The results largely support the PEG model, but attribute greater importance to early season temperature effects and later season grazing effects of Daphnia. In warmer treatments, the timing of phytoplankton and zooplankton peaks tended to be more closely coupled, and temperature did not affect the height of zooplankton peaks. In line with other experiments, these results do not support the widely held concern that warming may create a trophic mismatch between phytoplankton and zooplankton and reduce spring zooplankton production.

  • 265. Berger, Stella A
    et al.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Stibor, Herwig
    Trommer, Gabriele
    Ruhenstroth, Miriam
    Water temperature and stratification depth independently shift cardinal events during plankton spring succession2010Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 16, nr 7, s. 1954-1965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In deep temperate lakes, the beginning of the growing season is triggered by thermal stratification, which alleviates light limitation of planktonic producers in the surface layer and prevents heat loss to deeper strata. The sequence of subsequent phenological events (phytoplankton spring bloom, grazer peak, clearwater phase) results in part from coupled phytoplankton–grazer interactions. Disentangling the separate, direct effects of correlated climatic drivers (stratification-dependent underwater light climate vs. water temperature) from their indirect effects mediated through trophic feedbacks is impossible using observational field data, which challenges our understanding of global warming effects on seasonal plankton dynamics. We therefore manipulated water temperature and stratification depth independently in experimental field mesocosms containing ambient microplankton and inocula of the resident grazer Daphnia hyalina. Higher light availability in shallower surface layers accelerated primary production, warming accelerated consumption and growth of Daphnia, and both factors speeded up successional dynamics driven by trophic feedbacks. Specifically, phytoplankton peaked and decreased earlier and Daphnia populations increased and peaked earlier at both shallower stratification and higher temperature. The timing of ciliate dynamics was unrelated to both factors. Volumetric peak densities of phytoplankton, ciliates and Daphnia in the surface layer were also unaffected by temperature but declined with stratification depth in parallel with light availability. The latter relationship vanished, however, when population sizes were integrated over the entire water column. Overall our results suggest that, integrated over the entire water column of a deep lake, surface warming and shallower stratification independently speed up spring successional events, whereas the magnitudes of phytoplankton and zooplankton spring peaks are less sensitive to these factors. Therefore, accelerated dynamics under warming need not lead to a trophic mismatch (given similar grazer inocula at the time of stratification). We emphasize that entire water column dynamics must be studied to estimate global warming effects on lake ecosystems.

  • 266.
    Berggren, Andreas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ficedula hypoleuca hemoglobin levels in lead contaminated areas.: Is bird health affected by invertebrate community composition and abundance?2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Mining is a widespread industrial activity that in many cases, via mining wastes, leads to altered concentrations of metals in close vicinity to the mining activities. Metals in mining waste can have high toxicity and may persist in environments for long time periods. The presence of metals, such as lead (Pb), is known to contaminate and cause damage to nearby organisms and ecosystems. Birds are at risk of metal contamination and, since they are predators high up in the food chain, may face accumulation of metal in tissue over time, via consumption of contaminated prey. Small passerine species, such as the pied flycatcher (Ficedula hypoleuca), are suitable for studying metal contamination as they are ubiqutious, and high up in the food chain. Pied flycatchers feed exclusively on invertebrates, making the abundance, quality, and potential contamination of invertebrates interesting to study with regard to the health of the birds. Studies have shown that hemoglobin (Hb) levels in young pied flycatchers are reduced by high background levels of Pb.  This may be linked to prey availability and quality, as invertebrates are known to alter their composition, and contain higher Pb concentrations in Pb contaminated areas. Here, I investigated how invertebrate abundance and community composition, and pied flycatcher Hb concentrations (i.e. health), in reference and Pb contaminated areas, were related to each other. Invertebrate traps were set and sampled twice during the summer of 2018 to provide invertebrate data to the study. Bird Hb levels was acquired by taking blood samples from nearly fledged chicks in birdhouses placed in the different areas. I found a potential trend towards higher Hb levels in reference areas (p=0.110), suggesting that bird health is reduced by the presence of Pb, but this could not be explained by differences in invertebrate community composition or abundance (p>0.05). Hence, based on this study, high Pb concentrations in the soil does not directly, or indirectly via potential impacts on the prey community composition, influence the health of pied flycatchers.

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  • 267.
    Berggren, Johanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Stoftnedfall från gruvindustrin: En utvärdering av analysdata och undersökning av provtagningspunkter kring Aitikgruvan, Gällivare2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The purpose of this study was to investigate whether the sampling points for measuring airborne dust deposition in the Aitik copper mine - the largest, most effective opencast copper mining in Europe - are well located regarding efficiency to collect monitoring data. Issues that were addressed, among others, include background levels, weather impacts and possible external influence. The study was carried out by analyzing monitoring data covering a seven-year period (2010–2016). Dust-and copper levels, precipitation patterns, wind direction and wind speed were the parameters analyzed. A further look into the sampling points and their actual location in terrain was also made. The result of the study indicates, according to different aspects, on decreasing dust fall levels even though the production has increased. For instance, many of the 19 sampling points shows to have lower dust and copper levels according to a comparison of measurement data from 2010 to 2016. A correlation test showed that precipitation and wind does not have a strong connection to dust levels. On the other hand, wind speed showed to have a strong impact on dust fall levels under periods when the highest dust amounts were measured. Many of the sampling points also showed to have a strong connection to each other. The study concludes that a better dust control programme can be obtained if sampling points are reorganized along with a better method for calculating the dispersion of airborne dust.

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  • 268. Berggren, M.
    et al.
    Bengtson, P.
    Soares, A. R. A.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Climate Impacts Research Centre (CIRC).
    Terrestrial support of zooplankton biomass in northern rivers2018Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, nr 6, s. 2479-2492Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The contribution of terrestrially derived carbon to micro-crustacean zooplankton biomass (i.e., allochthony) has been previously studied in lakes, reservoirs, and estuaries, but little is known about zooplankton allochthony in rivers. In lacustrine environments, allochthony is regulated by distinct selective feeding behavior of different taxa. However, we hypothesized that restricted possibility for selective grazing in turbulent environments such as rivers would decouple zooplankton from specific microbial and algal food resources, such that their allochthony would mirror the terrestrial contribution to the surrounding bulk particle pool. We tested this idea by analyzing allochthony in 13 widely distributed Swedish rivers, using a dual-isotope mixing model. Zooplankton biomasses were generally low, and allochthony in different micro-crustacean groups (Cladocera, Cyclopoida, Calanoida) varied from 2% to 77%. As predicted, there were no correlations between allochthony and variables indicating the supply of algal and microbial food resources, such as chlorophyll a and bacterial production. Instead, the allochthony was generally similar to the share allochthonous contribution in bulk particulate organic matter, with relationships close to the 1 : 1 line. The zooplankton community allochthony was strongly regulated by the ecosystem metabolic balance between production and respiration, which in turn was dependent upon the ratio between total autochthonous organic carbon concentrations and water color. Our study for the first time shows that micro-crustacean allochthony is regulated differently in rivers compared to in lacustrine systems, and points to inefficient support of zooplankton biomass by algal resources in turbulent waters.

  • 269.
    Berggren, Maja
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bisfenol A i normalbefolkningen i Norr- & Västerbotten: Och en studie av om det finns samband mellan bisfenol A och rökning samt kolesterol2011Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 270.
    Berggren, Martin
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Bacterial use of allochthonous organic carbon for respiration and growth in boreal freshwater systems2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Aquatic systems worldwide receive large amounts of organic carbon from terrestrial sources. This ‘allochthonous’ organic carbon (AlloOC) affects critical physical and chemical properties of freshwater ecosystems, with consequences for food web structures and exchange of greenhouse gases with the atmosphere. In the boreal region, loadings of AlloOC are particularly high due to leaching from huge organic deposits in boreal forest, mire and tundra soils.

    A main process of AlloOC turnover in aquatic systems is its use by heterotrophic bacteria. Applying a bioassay approach, I measured the respiration and growth (production) of bacteria in northern Sweden, in streams and lakes almost totally dominated by AlloOC. The objective was to elucidate how variations in AlloOC source, age, composition and concentration impact on its use by aquatic bacteria, and how AlloOC properties, in turn, are regulated by landscape composition and by hydrology.

    The bacterial respiration (30-309 µg C L-1 d-1) was roughly proportional to the concentration of AlloOC (7-47 mg C L-1), but not significantly related to AlloOC source or character. Bacterial production (4-94 µg C L-1 d-1), on the other hand, was coupled to the AlloOC character, rather than concentration. A strong coupling to AlloOC character was also found for bacterial growth efficiency (0.06-0.51), i.e. production per unit of assimilated carbon. Bacterial production and growth efficiency increased with rising concentrations of low molecular weight AlloOC (carboxylic acids, free amino acids and simple carbohydrates). While the total AlloOC concentrations generally were the highest in mire-dominated catchments, low molecular weight AlloOC concentrations were much higher in forested catchments, compared to mire-dominated. These patterns were reflected in a strong landscape control of aquatic bacterial metabolism. Moreover, high flow episodes increased the export of organic carbon from forests, in relation to the export from mires, stimulating the bacterial production and growth efficiency in streams with mixed (forest and mire) catchments. The potential of AlloOC to support efficient bacterial growth decreased on time-scales of weeks to months, as the AlloOC was aged in laboratory or lake in situ conditions.

    To conclude, landscape, hydrology and conditions which determine AlloOC age have large influence on bacterial metabolism in boreal aquatic systems. Considering the role of bacteria in heterotrophic food chains, these factors can have spin-off effects on the structure and function of boreal aquatic ecosystems.

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  • 271. Berggren, Martin
    et al.
    Bergström, Ann-Kristin
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Intraspecific Autochthonous and Allochthonous Resource Use by Zooplankton in a Humic Lake during the Transitions between Winter, Summer and Fall2015Ingår i: PLOS ONE, E-ISSN 1932-6203, Vol. 10, nr 3, artikel-id e0120575Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seasonal patterns in assimilation of externally produced, allochthonous, organic matter into aquatic food webs are poorly understood, especially in brown-water lakes. We studied the allochthony (share biomass of terrestrial origin) in cladoceran, calanoid and cyclopoid micro-crustacean zooplankton from late winter to fall during two years in a small humic lake (Sweden). The use of allochthonous resources was important for sustaining a small population of calanoids in the water column during late winter. However, in summer the calanoids shifted to 100% herbivory, increasing their biomass several-fold by making efficient use of the pelagic primary production. In contrast, the cyclopoids and cladocerans remained at high levels of allochthony throughout the seasons, both groups showing the mean allochthony of 0.56 (range in mean 0.17-0.79 and 0.34-0.75, for the respective group, depending on model parameters). Our study shows that terrestrial organic matter can be an important resource for cyclopoids and cladocerans on an annual basis, forming a significant link between terrestrial organic matter and the higher trophic levels of the food web, but it can also be important for sustaining otherwise herbivorous calanoids during periods of low primary production in late winter.

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  • 272. Berggren, Martin
    et al.
    Gudasz, Cristian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Guillemette, Francois
    Hensgens, Geert
    Ye, Linlin
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Systematic microbial production of optically active dissolved organic matter in subarctic lake water2020Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 65, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ecology and biogeochemistry of lakes in the subarctic region are particularly sensitive to changes in the abundance and optical properties of dissolved organic matter (DOM). External input of colored DOM to these lakes is an extensively researched topic, but little is known about potential reciprocal feedbacks between the optical properties of DOM and internal microbial processes in the water. We performed 28-day dark laboratory incubation trials on water from 101 subarctic tundra lakes in northern Sweden, measuring the microbial decay of DOM and the resulting dynamics in colored (CDOM) and fluorescent (FDOM) DOM components. While losses in dissolved oxygen during the incubations corresponded to a 20% decrease in mean DOM, conversely the mean CDOM and total FDOM increased by 22% and 30%, respectively. However, the patterns in microbial transformation of the DOM were not the same in all lakes. Notably, along the gradient of increasing ambient CDOM (water brownness), the lakes showed decreased microbial production of protein-like fluorescence, lowered DOM turnover rates and decreasing bacterial growth per unit of DOM. These trends indicate that browning of subarctic lakes systematically change the way that bacteria interact with the ambient DOM pool. Our study underscores that there is no unidirectional causal link between microbial processes and DOM optical properties, but rather reciprocal dependence between the two.

  • 273.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Hjalmar, Laudon
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Aging of allochthonous organic carbon regulates bacterial production in unproductive boreal lakes2009Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, nr 4, s. 1333-1342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We calculated average aquatic dissolved organic carbon (DOC) age (the time span from soil discharge to observation) in water from the inlets and outlets of two unproductive Swedish lakes at different times during an annual cycle. Bacterial production (BP) and bacterial growth efficiency (BGE) determined during 7-d bioassays decreased with increasing average aquatic DOC age. Parallel to the declines in BP and BGE there was a rise in specific ultraviolet absorbance at the wavelength of 254 nm (SUVA254), which indicates that decreasing BP and BGE were connected to a shift to a more aromatic and recalcitrant DOC pool. The relationships between bacterial metabolism and DOC age were stronger after a Q10 correction of the DOC age, showing that temperature affected rates of DOC quality changes over time and should be taken into account when relating lake bacterial growth to substrate aging in natural environments. We propose that hydrological variability in combination with lake size (water renewal time) have a large influence on pelagic BP in lakes with high input of terrigenous DOC.

  • 274. Berggren, Martin
    et al.
    Klaus, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Selvam, Balathandayuthabani Panneer
    Ström, Lena
    Laudon, Hjalmar
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes2018Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, nr 2, s. 457-470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in changes in DOC composition and pigmentation (color). However, the process-based understanding of these changes is incomplete, especially for headwater lakes. We hypothesized that because heterotrophic bacteria preferentially consume noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend on the relative importance of these two processes, accordingly. To test this hypothesis we combined laboratory experiments with field studies in nine boreal lakes, assessing both the relative importance of different DOC decay processes (biological or photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net losses of colored DOC. However, in highly pigmented brown-water lakes (absorbance at 420 nm > 7 m(-1)) biological processes dominated, and there was no systematic relationship between color loss and WTT. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes.

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  • 275.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Laudon, Hjalmar
    Skogens ekologi och skötsel, SLU, Umeå.
    Haei, Mahsa
    Skogens ekologi och skötsel, SLU, Umeå.
    Ström, Lena
    Naturgeografi och Ekosystemanalys, Lunds universitet, Lund.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Efficient aquatic bacterial metabolism of dissolved low-molecular-weight compounds from terrestrial sources2010Ingår i: The ISME Journal, ISSN 1751-7362, Vol. 4, nr 3, s. 408-416Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carboxylic acids (CAs), amino acids (AAs) and carbohydrates (CHs) in dissolved free forms can be readily assimilated by aquatic bacteria and metabolized at high growth efficiencies. Previous studies have shown that these low-molecular-weight (LMW) substrates are released by phytoplankton but also that unidentified LMW compounds of terrestrial origin is a subsidy for bacterial metabolism in unproductive freshwater systems. We tested the hypothesis that different terrestrially derived CA, AA and CH compounds can offer substantial support for aquatic bacterial metabolism in fresh waters that are dominated by allochthonous dissolved organic matter (DOM). Drainage water from three catchments of different characters in the Krycklan experimental area in Northern Sweden were studied at the rising and falling limb of the spring flood, using a 2-week bioassay approach. A variety of CA, AA and CH compounds were significantly assimilated by bacteria, meeting 15–100% of the bacterial carbon demand and explaining most of the observed variation in bacterial growth efficiency (BGE; R2=0.66). Of the 29 chemical species that was detected, acetate was the most important, representing 45% of the total bacterial consumption of all LMW compounds. We suggest that LMW organic compounds in boreal spring flood drainage could potentially support all in situ bacterial production in receiving lake waters during periods of weeks to months after the spring flood.

  • 276.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Laudon, Hjalmar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bacterial utilization of imported organic material in three small nested humic lakes2010Ingår i: INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL 30, PT 9 / [ed] Jones J, Faaborg J, Stuttgart: E SCHWEIZERBART'SCHE VERLAGSBUCHHANDLUNG , 2010, Vol. 30, nr 9, s. 1393-1396Konferensbidrag (Refereegranskat)
  • 277.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Laudon, Hjalmar
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Hydrological control of organic carbon support for bacterial growth in boreal headwater streams2009Ingår i: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 57, nr 1, s. 170-178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Terrestrial organic carbon is exported to freshwater systems where it serves as substrate for bacterial growth. Temporal variations in the terrigenous organic carbon support for aquatic bacteria are not well understood. In this paper, we demonstrate how the combined influence of landscape characteristics and hydrology can shape such variations. Using a 13-day bioassay approach, the production and respiration of bacteria were measured in water samples from six small Swedish streams (64° N, 19° E), draining coniferous forests, peat mires, and mixed catchments with typical boreal proportions between forest and mire coverage. Forest drainage supported higher bacterial production and higher bacterial growth efficiency than drainage from mires. The areal export of organic carbon was several times higher from mire than from forest at low runoff, while there was no difference at high flow. As a consequence, mixed streams (catchments including both mire and forest) were dominated by mire organic carbon with low support of bacterial production at low discharge situations but dominated by forest carbon supporting higher bacterial production at high flow. The stimulation of bacterial growth during high-flow episodes was a result of higher relative export of organic carbon via forest drainage rather than increased drainage of specific “high-quality” carbon pools in mire or forest soils.

  • 278.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Laudon, Hjalmar
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Landscape regulation of bacterial growth efficiency in boreal freshwaters2007Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Allochthonous organic carbon in aquatic systems is metabolized by heterotrophic bacteria, with significant consequences for the biostructure and energy pathways of freshwater ecosystems. The degree to which allochthonous substrates support growth of bacteria is largely dependent on bacterial growth efficiency (BGE), i.e., bacterial production (BP) per unit of assimilated carbon. Here we show how the spatial variability of BGE in the boreal region can be mediated by the distribution of the two dominating landscape elements forest and mires. Using an 11 days bioassay approach, the production and respiration of bacteria were measured in water samples from nine small Swedish streams (64°N 19°E), representing a gradient ranging from organic carbon supplied mainly from peat mires to carbon supplied mainly from coniferous forests. BP was positively correlated to forest coverage (%) of the catchment, while bacterial respiration was similar in all streams. Consequently, BGE showed a strong positive correlation with forest coverage. Partial least square regression showed that BGE was chiefly regulated by qualitative properties of the organic material, indicated by the absorbance ratio a254/a365 plus C/N and C/P ratios. The data suggest that a share of the organic carbon pool, drained mainly from forest soils, had a potential of being incorporated into bacterial biomass with great efficiency. Its potential for supporting growth was probably nutrient regulated as indicated by inorganic nutrient enrichment experiments.

  • 279.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Laudon, Hjalmar
    Department of Forest Ecology and Management, SLU, Umeå.
    Jonsson, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Nutrient constraints on metabolism affect the temperature regulation of aquatic bacterial growth efficiency2010Ingår i: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 60, nr 4, s. 894-902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inorganic nutrient availability and temperature are recognized as major regulators of organic carbon processing by aquatic bacteria, but little is known about how these two factors interact to control bacterial metabolic processes. We manipulated the temperature of boreal humic stream water samples within 0–25°C and measured bacterial production (BP) and respiration (BR) with and without inorganic nitrogen + phosphorus addition. Both BP and BR increased exponentially with temperature in all experiments, with Q 10 values varying between 1.2 and 2.4. The bacterial growth efficiency (BGE) showed strong negative relationships with temperature in nutrient-enriched samples and in natural stream water where community-level BP and BR were not limited by nutrients. However, there were no relationships between BGE and temperature in samples where BP and BR were significantly constrained by the inorganic nutrient availability. The results suggest that metabolic responses of aquatic bacterial communities to temperature variations can be strongly dependent on whether the bacterial metabolism is limited by inorganic nutrients or not. Such responses can have consequences for both the carbon flux through aquatic food webs and for the flux of CO2 from aquatic systems to the atmosphere.

  • 280. Berggren, Martin
    et al.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Soares, Ana R. Alves
    Bergström, Ann-Kristin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Toward an ecologically meaningful view of resource stoichiometry in DOM-dominated aquatic systems2015Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 37, nr 3, s. 489-499Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Research on nutrient controls of planktonic productivity tends to focus on a few standard fractions of inorganic or total nitrogen (N) and phosphorus (P). However, there is a wide range in the degree to which land-derived dissolved organic nutrients can be assimilated by biota. Thus, in systems where such fractions form a majority of the macronutrient resource pool, including many boreal inland waters and estuaries, our understanding of bacterio-and phytoplankton production dynamics remains limited. To adequately predict aquatic productivity in a changing environment, improved standard methods are needed for determining the sizes of active (bioavailable) pools of N, P and organic carbon (C). A synthesis of current knowledge suggests that variation in the C:N:P stoichiometry of bioavailable resources is associated with diverse processes that differentially influence the individual elements across space and time. Due to a generally increasing organic nutrient bioavailability from C to N to P, we hypothesize that the C:N and N:P of bulk resources often vastly overestimates the corresponding ratios of bioavailable resources. It is further proposed that basal planktonic production is regulated by variation in the source, magnitude and timing of terrestrial runoff, through processes that have so far been poorly described.

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  • 281.
    Berggren, Martin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ström, L
    Laudon, H
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jonsson, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bergström, Ann-Kristin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lake secondary production fueled by rapid transfer of low molecular weight organic carbon from terrestrial sources to aquatic consumers2010Ingår i: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 13, nr 7, s. 870-880Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ecology Letters (2010) Abstract Carbon of terrestrial origin often makes up a significant share of consumer biomass in unproductive lake ecosystems. However, the mechanisms for terrestrial support of lake secondary production are largely unclear. By using a modelling approach, we show that terrestrial export of dissolved labile low molecular weight carbon (LMWC) compounds supported 80% (34-95%), 54% (19-90%) and 23% (7-45%) of the secondary production by bacteria, protozoa and metazoa, respectively, in a 7-km(2) boreal lake (conservative to liberal estimates in brackets). Bacterial growth on LMWC was of similar magnitude as that of primary production (PP), and grazing on bacteria effectively channelled the LMWC carbon to higher trophic levels. We suggest that rapid turnover of forest LMWC pools enables continuous export of fresh photosynthates and other labile metabolites to aquatic systems, and that substantial transfer of LMWC from terrestrial sources to lake consumers can occur within a few days. Sequestration of LMWC of terrestrial origin, thus, helps explain high shares of terrestrial carbon in lake organisms and implies that lake food webs can be closely dependent on recent terrestrial PP.

  • 282.
    Berggren, Martin
    et al.
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
    Ye, Linlin
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden; School of Geographic Sciences, Nantong University, Nantong, China.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bergström, Ann-Kristin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Verheijen, Hendricus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Hensgens, Geert
    Department of Earth Sciences, Vrije Universiteit, Amsterdam, Netherlands.
    Nutrient limitation masks the dissolved organic matter composition effects on bacterial metabolism in unproductive freshwaters2023Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 68, nr 9, s. 2059-2069Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aquatic microbial responses to changes in the amount and composition of dissolved organic carbon (DOC) are of fundamental ecological and biogeochemical importance. Parallel factor (PARAFAC) analysis of excitation–emission fluorescence spectra is a common tool to characterize DOC, yet its ability to predict bacterial production (BP), bacterial respiration (BR), and bacterial growth efficiency (BGE) vary widely, potentially because inorganic nutrient limitation decouples microbial processes from their dependence on DOC composition. We used 28-d bioassays with water from 19 lakes, streams, and rivers in northern Sweden to test how much the links between bacterial metabolism and fluorescence PARAFAC components depend on experimental additions of inorganic nutrients. We found a significant interaction effect between nutrient addition and fluorescence on carbon-specific BP, and weak evidence for influence on BGE by the same interaction (p = 0.1), but no corresponding interaction effect on BR. A practical implication of this interaction was that fluorescence components could explain more than twice as much of the variability in carbon-specific BP (R2 = 0.90) and BGE (R2 = 0.70) after nitrogen and phosphorus addition, compared with control incubations. Our results suggest that an increased supply of labile DOC relative to ambient phosphorus and nitrogen induces gradually larger degrees of nutrient limitation of BP, which in turn decouple BP and BGE from fluorescence signals. Thus, while fluorescence does contain precise information about the degree to which DOC can support microbial processes, this information may be hidden in field studies due to nutrient limitation of bacterial metabolism.

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    fulltext
  • 283.
    Berggren, Sally
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lokalt eller hållbart producerat?: Jämförelse mellan koldioxidutsläpp från två alternativa trävirke för brobygge över Skellefteälven.2022Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Emissions of greenhouse gasses, such as carbon dioxide, have been shown to be strongly connected global warming. In 2020 the European Union adopted the goal of reducing emissions of greenhouse gasses to a net of zero before year 2050. This is essential for keeping the average global temperature rise below 1.5 degrees. A large source of carbon dioxide emissions in Sweden is the forestry sector. The carbon balance in ecosystems is usually disturbed due to clear-cutting, which is the main silvicultural system used in Sweden. Introducing more sustainable silvicultural systems, such as continuous cover forestry, is a measure that authorities advocate. This study aimed to examine emissions of carbon dioxide from two timber sources that may be used for a bridge construction in Skellefteå. The timber would either come from a local clear-cut, transported by truck, or from continuous cover forestry in Lithuania, transported to Sweden by ship. The result is based on literature and calculations on data from previous studies. The results showed effects on carbon balance due to different silvicultural systems are complex, though the alternative with continuous cover forestry seemed to contribute to less emissions, despite the timber not being locally produced. The main factor between the systems, and therefore the different levels of emissions, seems to be highly dependent on how much of the harvested trees that is suitable for timber. However, emissions will also depend on local conditions such as timber storage. Therefore, it is important to take this into account when comparing silvicultural systems. 

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  • 284.
    Berggren, Åsa
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Hållbart skogsbruk i Robertsfors kommun - Är kontinuerligt skogsbruk en väg att gå?2006Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 285.
    Bergknut, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wiberg, Karin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Vertical and lateral redistribution of POPs in soils developed along a hydrological gradient2011Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 45, nr 24, s. 10378-10384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Study of the dispersion of persistent organic pollutants (POPs) throughout the environment is necessitated by their toxicological properties and propensity to accumulate in biota. In this study, we use data from the analysis of three (210)Pb dated soil profiles collected along a 30-m hydrological gradient to demonstrate postdepositional mobility of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs). We found that (i) humus originating from litter exposed to surface fallout during the 1960-1970s contains the highest concentrations of PCDD/Fs and PCBs in the O-horizon of the soils; (ii) accumulation rates of PCDD/Fs and PCBs in the O-horizon (similar to 5.0 and similar to 210 mu g m(-2) yr(-1)) constituted only 9.1% and 3.5%, respectively, of the measured annual input, demonstrating that a minor fraction of the deposited material is retained within the O-horizon; (iii) POP inventories in the upper 0.5-0.9 m of the mineral soil constituted a considerable part (40-70%) of the total pool stored in the soil, implying significant vertical translocation of atmospheric derived POPs; and (iv) increasing downslope inventories of POPs suggest a lateral downward transport of POPs from uphill soils. The findings challenge the commonly accepted view that POPs fallout is effectively retained within O-horizons.

  • 286.
    Berglund, Bobby
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Länsstyrelsens arbete med anmälningsärenden inom djurskyddet: Kan andelen obefogade ärenden sänkas?2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The county administrative boards work with notification errands within animal welfare: Can the proportion of unjustified notifications be lowered?

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    fulltext
  • 287.
    Berglund, Dennis
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    När bildas is?: En studie om ispredicering och faktorer som påverkar isbildning2023Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    An improved knowledge regarding what spatial scale temperature data is needed for ice-prediction would improve calculations how ice-coverage has been affected over time. Which by extension would give insight how ice might response to climate change. The purpose of this study was to find out if ice-growth in Sävar River could be explained by both local and regional temperature data, and what factors beyond temperature affect ice-growth. To accomplish this, I analyzed time-lapse photos from Sävar River during a three-month period. I found out that the use of regional temperature data to explain ice-growth on a local scale is limited due to the differences in accumulated degrees. The local temperature data measurement accumulated -2281 °C from ice began to grow until the whole channel was ice-covered and the regional temperature data accumulated -1901 °C under the same period. My findings support the assumption that frazil ice in large concentrations seem to increase ice-growth. Furthermore, no relation between ice-growth/decrease and precipitation or wet spots was found in this study.

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  • 288. Berglund, H
    et al.
    Edman, M
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ericson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Temporal variation in wood-fungi diversity in boreal old-growth forests: implications for monitoring2005Ingår i: Ecological Applications, Vol. 15, s. 970-982Artikel i tidskrift (Refereegranskat)
  • 289. Berglund, Håkan
    et al.
    Jonsson, Bengt-Gunnar
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Erratum: Nested plant and fungal communities; the importance of area and habitat quality in maximizing species capture in boreal old-growth forests (Biological Conservation 112:3 (319-328) DOI: 10.1016/S0006-3207(02)00329-4)2004Ingår i: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 117, nr 5, s. 563-565Artikel i tidskrift (Refereegranskat)
  • 290.
    Berglund, Johan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Omställning av Bredviksbergets avfallsanläggning i Piteå inför förbudet att deponera flytande avfall2004Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 291.
    Berglund, Johnny
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pelagic microorganisms in the northern Baltic Sea: Ecology, diversity and food web dynamics2005Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Heterotrophic microorganisms are important for the flow of carbon and nutrients in the sea. Bacteria, nanoflagellates and ciliates are relevant components of the pelagic food web. In order to be able to predict the outcome of e.g. eutrophication or climate change we need to know how the different components of the pelagic food web are regulated. With the focus on the northern Baltic Sea food web, this thesis deals with limitation and control of heterotrophic protists, the effect of resource heterogeneity on food web efficiency and diversity of nanoflagellates.

    In-situ microcosm experiments showed that the net growth of heterotrophic flagellates were resource limited throughout the year. Field data confirmed that the abundance of flagellates was bottom-up controlled. Furthermore, field data also showed that the annual average biomass of protists, flagellates and ciliates increased with primary productivity. On a smaller seasonal scale temperature and bacterial biomass were able to explain most of the variation in flagellate biovolume. The temporal variation in ciliate biovolume could not be explained by any bottom-up factors like bacterial biomass, flagellate biomass or chlorophyll a. This and an in-situ microcosm experiment implied that the seasonal dynamics of ciliates were more regulated by predators like mesozooplankton.

    The food web efficiency i.e. how much of production at the resource level is converted to production at the top trophic level, may be affected by specific size or type of resource. Indoor mesocosms revealed that the food web efficiency was 11 times lower when heterotrophic bacteria dominated basal production instead of nano- and micro-sized phytoplankton. This was due to a lengthening of the food web when pico-sized bacteria constituted the main resource.

    The PCR-DGGE molecular biological method was used to study the diversity of heterotrophic or mixotrophic chrysomonads. The focus was set on chrysomonads due to their relatively large contribution to the nanoflagellate community. Group-specific PCR primers were optimized for the target group. A field survey in the northern Baltic Sea showed that a handful of chrysomonad sequences were present throughout the year. Significantly more chrysomonads were recorded in the basin with higher primary productive and salinity. In total 15-16 different chrysomonad sequences were recorded. Most of them matched uncultured chrysomonad clones.

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    FULLTEXT01
  • 292.
    Berglund, Johnny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Jürgens, Klaus
    Bruchmüller, Iris
    Wedin, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Use of group-specific PCR primers for identification of chrysophytes by denaturing gradient gel electrophoresis2005Ingår i: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, ISSN 0948-3055, Vol. 39, nr 2, s. 171-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The chrysophytes Chrysophyceae and Synurophyceae are ecologically important groups of autotrophic, mixotrophic and heterotrophic flagellates. The smallest forms are difficult to identify by classical microscopy but have important functions both as primary producers and as consumers of bacteria in the aquatic food chain. Group-specific primers for amplification of the 18S small sub-unit rRNA gene were developed for analysis of chrysophyte diversity by denaturing gradient gel electrophoresis (DGGE). Two different primer pairs were tested. The first primer pair (EukC1-F–Chryso-R) primarily targeted Paraphysomonadaceae and Ochromonadales, which generally have heterotrophic or mixotrophic nutrition. The second primer pair (EukC2-F–Chryso-R) targeted both Chrysophyceae and Synurophyceae. The primer pairs were tested for PCR amplification of the 18S rRNA gene of 25 cultured chrysophyte species and 6 other closely related nanoplanktonic species. Both primer pairs performed well, since PCR products were obtained for the corresponding chrysophyte cultures. None of the non-chrysophyte species were amplified with these primers. PCR products of chrysophyte cultures could be separated by DGGE in a denaturing gradient from 40 to 60%. In order to test this PCR-DGGE system for natural planktonic systems, we used field samples from a brackish water area (Baltic Sea) and a freshwater lake. The most intense DGGE bands were excised, sequenced and compared to sequences in GenBank. All obtained sequences grouped within the chrysophytes. Thus, the method seems to be promising for examining chrysophyte diversity in planktonic systems.

  • 293.
    Berglund, Johnny
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Müren, Umut
    Båmstedt, Ulf
    Andersson, Agneta
    Efficiency of a phytoplankton and bacterial-based food web in a pelagic marine ecosystemManuskript (Övrigt vetenskapligt)
  • 294.
    Berglund, Johnny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Müren, Umut
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Båmstedt, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Efficiency of a phytoplankton-based and a bacterial-based food web in a pelagic marine system2007Ingår i: Limnology and Oceanography, Vol. 52, nr 1, s. 121-131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    he food web efficiency in two contrasting food webs, one phytoplankton based and one bacteria based, was studied in a mesocosm experiment using seawater from the northern Baltic Sea. Organisms included in the experiment were bacteria, phytoplankton, protozoa, and mesozooplankton (copepods). A phytoplankton-based food web was generated by incubating at a high light level with the addition of nitrogen and phosphorus (NP). A bacteria-based food web was created by adding carbon, nitrogen, and phosphorus (CNP) and incubating at a lower light level. In the CNP treatment bacteria dominated the productivity (91%), while in the NP treatment phytoplankton were dominant producers (74%). The phytoplankton community in the NP treatment was dominated by autotrophic nanoflagellates. The food web efficiency, defined as mesozooplankton productivity per basal productivity (phytoplankton + bacteria), was 22% in the phytoplankton-based food web and 2% in the bacteria-based food web. This discrepancy could be explained by 1�xtra trophic levels in the bacteria-based food web where carbon passed through flagellates and ciliates before reaching mesozooplankton, while in the phytoplankton-based food web there was a direct pathway from phytoplankton to mesozooplankton. The results were supported by stable isotope analysis of mesozooplankton. We propose that climate change, with increased precipitation and river runoff in the Baltic Sea, might favor a bacteria-based food web and thereby reduce pelagic productivity at higher trophic levels.

  • 295.
    Berglund, Johnny
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Samuelsson, Kristina
    Kruys, Åsa
    Andersson, Agneta
    Spatial and temporal variation of chrysomonads in the northern Baltic Sea estimated by DGGE and epifluorescence microscopyManuskript (Övrigt vetenskapligt)
  • 296.
    Berglund, Johnny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Samuelsson, Kristina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Kull, Tomas
    Muren, Umut
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Relative strength of resource and predation limitation of heterotrophic nanoflagellates in a low-productive sea area2005Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 27, nr 9, s. 923-935Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The magnitude of resource and predation limitation of heterotrophic nanoflagellates (HNF) was studied in two short-term enclosure experiments performed in a low-productive sea area in the northern Baltic Sea in 2001. A cross-factorial design was used to simultaneously assess the relative importance of the two factors. Resource limitation was removed by adding bacteria, and predation limitation was eliminated by selective filtration. The first experiment was performed in June just after the spring bloom decline and the second in September at the end of the productive season. Resource limitation prevailed during both experiments, contributing to 60% of the net growth increase in June and 74% in September. Removal of predators had a significant effect only in June. Evidence for simultaneous resource and predation limitation was thus found only during the post-bloom situation. The results were applied to a model on resource and predation control of HNF abundances. To evaluate seasonal differences, field data on HNF and bacteria from a whole year study were applied to the model. Except for a few occasions during spring, the model indicated prevailing resource control of HNF at two locations with slightly different productivity.

  • 297.
    Berglund, Louise
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Riparian Vegetation Distribution along the Ume River: Predicted responses of riparian plants to environmental flow modifications in run-of-river impoundments2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Älvmiljöer utgör komplexa och dynamiska ekosystem som tillhandahåller värdefulla ekosystemtjänster så som rent vatten. Den artrika strandvegetation bidrar till många viktiga ekosystemsfunktioner som närings- och giftupptag och till minskad erosion. Vattenregleringen med förändrade flödesregimer har minskat artrikedom, täckningsgrad och tillväxt av strandväxter. För restaurering av strandekosystemen kan omreglering till mer naturliga säsongsvariationer i vattenståndet vara nödvändigt. Den här studien syftade till att förutsäga hur utbredningen av strandväxter längs stränder i vattenkraftsmagasin potentiellt skulle förändras vid användande av miljöanpassade flöden för att mer likna naturliga flödesregimer i outbyggda älvar. Jag undersökte växternas utbredning i höjdled på stranden längs två magasin i Umeälven och beräknade sannolikheten för varje arts förekomst längs strandens översvämningsgradient. Av de arter som förekom i både Umeälven och den närliggande, outbyggda Vindelälven jämfördes växternas utbredningsgränser i respektive älv. De flesta arterna uppvisade liknande översvämningstolerans i Umeälven och Vindelälven. För att förutsäga förändringar i utbredning som respons på tre olika simulerade miljöanpassade vattenståndsregimer, jämfördes arternas översvämningstolerans vid nuvarade vattenstånd med simulerade vattenståndsregimer. En simulerad vårflod och lågt vattenstånd under sensommaren förväntas ge de största responserna i artutbredning med ökningar på 70-80% för ett flertal strandväxter. Endast 47% av älvstränderna i magasinen i Umeälven bedöms vara lämpliga för växtetablering eftersom stora delar av strandsträckorna är branta och saknar finkornigt substrat till följd av erosion.

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    Berglund_2014
  • 298.
    Berglund, Louise
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Växtsamhällen på osorterade cirklar i Abisko: Hur förändrad kryogen aktivitet kan påverka sammansättning och artrikedom av kärlväxter2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Non-sorted circles are patterned ground features created by cryogenic activity in alpine and arctic areas. In these features, cryogenic activity controls vegetation communities by causing repeated disturbance and therefore provides habitat for species that are poor competitors but can tolerate disturbance. A recent study has shown that there is a trend where shrub vegetation overgrows the bare soil found within non-sorted circles. The aim of this study was to assess how the vascular plant communities on non-sorted circles have changed since 1985 and determine to what extent cryogenic activity affect vegetation communities. The study was conducted in Abisko and the point frame method was used to re-investigate how the plant species composition and richness have changed between 1985 and 2012, while a visual frame method was used to investigate how the plant communities change along a gradient of cryogenic activity. The results showed that the vascular plant communities on non-sorted circles in Abisko have changed since 1985 with a decrease in poorly competitive species, and an increase in competitive species. My results suggest that species richness is favoured by cryogenic activity, as the highest species richness was found on intermediately disturbed sites and on the transition zone between bare soil and fully developed vegetation cover. My findings indicate that poorly competitive species will lose habitat and become outcompeted by other species when cryogenic activity decreases, and therefore I conclude that there is a risk of local loss in vascular plant species richness in alpine areas.

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    Berglund_2013
  • 299.
    Berglund, Malin
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    A Waste Management Plan for Recycling in Gwanda, Zimbabwe2004Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    A waste management plan for recycling in Gwanda, Zimbabwe

    The city of Gwanda in Zimbabwe is facing problems such as insufficient, unreliable and improper waste management. The refuse collection is working inadequately, the town is experiencing a major problem regarding littering and the current refuse dump is not working satisfactorily. The main purpose of this study was to design a recycling model for Gwanda town. To achieve this, an inventory of the recycling market was performed, an investigation of what kinds of refuse Gwanda town generates was made, recycling companies able to collect specific categories of recyclables were identified and a recycling station was designed, where the material to be recycled could be gathered before collection. The study shows that paper and plastic are the most suitable waste categories to commence recycling in Gwanda. According to the proposed plan, a recycling depot will be established that is centrally situated in town, close to the sources of waste. The project will be community based and operated by youths, who will move around to stores and institutions within town collecting the recyclable material. Only the schools will be able to sell recyclables to the depot. Two recovering companies will purchase and collect the waste paper and plastic gathered at the depot. The project will benefit the youths by providing employment opportunities, the stakeholders (commerce, institutions) will benefit by reduced waste removal costs and the schools, through the profits they receive from selling recyclables to the depot. The local authority and the citizens will benefit immensely by enjoying streets free from litter and also reduced amount of waste disposed at the refuse dump. The lifetime of the refuse dump will be increased and the project will contribute to the preservation of natural resources and also to the development of a sustainable society.

  • 300.
    Berglund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Vad styr älgars betesmönster?: Hur älgbetesskador på tall påverkas av tallungskogars rumsliga fördelning och areal2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    One of the largest challenges humanity faces today is reducing CO₂-emissions to mitigate climate change. Part of the solution might be to increase the use of wood products. To do this, the efficiency of forestry has to be improved. In Sweden, a large obstacle for improving the efficiency of forestry is moose, or rather the damages its browsing causes on Scots pine. The aim of this study was to investigate how stand size and stand isolation affects the intensity of moose browsing damage on Scots pine. In addition, effects from tree density, stand age, and interactions between the different factors were investigated. This was done by using data from forest companies and field data collected from 29 Scots pine stands in central Sweden. The data were analysed in a multiple regression analysis, selecting the model that best explained variation in browsing damage. Results show that browsing damage was lower in more isolated stands. Stand size, however, did not have an effect on browsing damage. The factors stand age and Scots pine density had positive effects on the amount of browsing damage, but effects from stand age decreased with increasing pine density. In total, 77% of the variance in browsing damage was explained by the best model. In order to decrease browsing damage on Scots pine, I suggest that land owners take coordinated action to avoid creating large areas of young pine stands within the same area.

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    fulltext
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