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  • 301. Drotz, Marcus K.
    et al.
    Brodin, Tomas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Saura, Anssi
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Giles, Barbara E.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ecotype Differentiation in the Face of Gene Flow within the Diving Beetle Agabus bipustulatus (Linnaeus, 1767) in Northern Scandinavia2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 2, p. e31381-Article in journal (Refereed)
    Abstract [en]

    The repeated occurrence of habitat-specific polyphyletic evolved ecotypes throughout the ranges of widely distributed species implies that multiple, independent and parallel selection events have taken place. Ecological transitions across altitudinal gradients over short geographical distances are often associated with variation in habitat-related fitness, these patterns suggest the action of strong selective forces. Genetic markers will therefore contribute differently to differences between ecotypes in local hybrid zones. Here we have studied the adaptive divergence between ecotypes of the water beetle Agabus bipustulatus along several parallel altitudinal gradients in northern Scandinavia. This water beetle is well known for its remarkable morphological variation associated with mountain regions throughout the western Palaearctic. Two morphological ecotypes are recognised: a montane type with reduced flight muscles and a lowland type with fully developed muscles. Using a multilocus survey of allozyme variation and a morphological analysis with landmark-based morphometrics, across thirty-three populations and seven altitudinal gradients, we studied the local adaptive process of gene flow and selection in detail. Populations were sampled at three different elevations: below, at and above the tree line. The results indicate that the levels of divergence observed between ecotypes in morphology and allele frequencies at alpha-Glycerophosphate dehydrogenase relative to those shown by neutral molecular markers reflects local diversifying selection in situ. Four main lines of evidence are shown here: (1) A repeated morphological pattern of differentiation is observed across all altitudinal transects, with high reclassification probabilities. (2) Allele and genotype frequencies at the alpha-Gpdh locus are strongly correlated with altitude, in sharp contrast to the presumable neutral markers. (3) Genetic differentiation is two to three times higher among populations across the tree line than among populations at or below. (4) Genetic differentiation between ecotypes within independent mountain areas is reflected by different sets of allozymes.

  • 302. Du, Shuhui
    et al.
    Wang, Zhaoshan
    Ingvarsson, Pär K
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Wang, Dongsheng
    Wang, Junhui
    Wu, Zhiqiang
    Tembrock, Luke R.
    Zhang, Jianguo
    Multilocus analysis of nucleotide variation and speciation in three closely related Populus (Salicaceae) species2015In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 24, no 19, p. 4994-5005Article in journal (Refereed)
    Abstract [en]

    Historical tectonism and climate oscillations can isolate and contract the geographical distributions of many plant species, and they are even known to trigger species divergence and ultimately speciation. Here, we estimated the nucleotide variation and speciation in three closely related Populus species, Populus tremuloides, P.tremula and P.davidiana, distributed in North America and Eurasia. We analysed the sequence variation in six single-copy nuclear loci and three chloroplast (cpDNA) fragments in 497 individuals sampled from 33 populations of these three species across their geographic distributions. These three Populus species harboured relatively high levels of nucleotide diversity and showed high levels of nucleotide differentiation. Phylogenetic analysis revealed that P.tremuloides diverged earlier than the other two species. The cpDNA haplotype network result clearly illustrated the dispersal route from North America to eastern Asia and then into Europe. Molecular dating results confirmed that the divergence of these three species coincided with the sundering of the Bering land bridge in the late Miocene and a rapid uplift of the Qinghai-Tibetan Plateau around the Miocene/Pliocene boundary. Vicariance-driven successful allopatric speciation resulting from historical tectonism and climate oscillations most likely played roles inthe formation of the disjunct distributions and divergence of these three Populus species.

  • 303. Dunn, RM
    et al.
    Colwell, RK
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The river domain: why are there more species halfway up the river?2006In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 29, no 2, p. 251-259Article in journal (Refereed)
  • 304.
    Dupont, Chris L.
    et al.
    J. Craig Venter Institute, USA.
    Larsson, John
    Stockholm University.
    Yooseph, Shibu
    J. Craig Venter Institute, USA.
    Ininbergs, Karolina
    Stockholm University.
    Goll, Johannes
    J. Craig Venter Institute, USA.
    Asplund-Samuelsson, Johannes
    Stockholm University.
    McCrow, John P.
    J. Craig Venter Institute, USA.
    Celepli, Narin
    Stockholm University.
    Allen, Lisa Zeigler
    J. Craig Venter Institute, USA.
    Ekman, Martin
    Stockholm University.
    Lucas, Andrew J.
    Hagström, Åke
    University of Gothenburg.
    Thiagarajan, Mathangi
    Brindefalk, Bjorn
    Richter, Alexander R.
    Andersson, Anders F.
    Tenney, Aaron
    Lundin, Daniel
    KTH Royal Institute of Technology.
    Tovchigrechko, Andrey
    Nylander, Johan A. A.
    Brami, Daniel
    Badger, Jonathan H.
    Allen, Andrew E.
    Rusch, Douglas B.
    Hoffman, Jeff
    Norrby, Erling
    Friedman, Robert
    Pinhassi, Jarone
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Venter, J. Craig
    Bergman, Birgitta
    Functional Tradeoffs Underpin Salinity-Driven Divergence in Microbial Community Composition2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 2, article id e89549Article in journal (Refereed)
    Abstract [en]

    Bacterial community composition and functional potential change subtly across gradients in the surface ocean. In contrast, while there are significant phylogenetic divergences between communities from freshwater and marine habitats, the underlying mechanisms to this phylogenetic structuring yet remain unknown. We hypothesized that the functional potential of natural bacterial communities is linked to this striking divide between microbiomes. To test this hypothesis, metagenomic sequencing of microbial communities along a 1,800 km transect in the Baltic Sea area, encompassing a continuous natural salinity gradient from limnic to fully marine conditions, was explored. Multivariate statistical analyses showed that salinity is the main determinant of dramatic changes in microbial community composition, but also of large scale changes in core metabolic functions of bacteria. Strikingly, genetically and metabolically different pathways for key metabolic processes, such as respiration, biosynthesis of quinones and isoprenoids, glycolysis and osmolyte transport, were differentially abundant at high and low salinities. These shifts in functional capacities were observed at multiple taxonomic levels and within dominant bacterial phyla, while bacteria, such as SAR11, were able to adapt to the entire salinity gradient. We propose that the large differences in central metabolism required at high and low salinities dictate the striking divide between freshwater and marine microbiomes, and that the ability to inhabit different salinity regimes evolved early during bacterial phylogenetic differentiation. These findings significantly advance our understanding of microbial distributions and stress the need to incorporate salinity in future climate change models that predict increased levels of precipitation and a reduction in salinity.

  • 305.
    Dynesius, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Slow recovery of bryophyte assemblages in middle-aged boreal forests regrown after clear-cutting2015In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 191, p. 101-109Article in journal (Refereed)
    Abstract [en]

    Clear-cutting followed by even-aged forestry is transforming forests around the globe. There is growing concern that considerable parts of the native forest biodiversity will not be able to re-colonize these new stands before the next clear-cutting. The development of species assemblages during the full forestry rotation period must be understood in order to assess the need for management adaptations and to get a basis for their design. Knowledge is accumulating from studies of permanent plots before and shortly after clear-cutting, but for later stages only comparative studies have been published (space-for-time substitutions). In this study, I combined this comparative approach with direct monitoring of the pace of assemblage recovery in boreal stands regrown after clear-cutting half a century ago (treatment stands). I found little re-colonization in assemblages of mosses and liverworts between an initial survey to a resurvey 15 years later in 0.1-ha permanent plots of upland and stream-side forest. The assemblages of the treatment stands were still significantly different from those in matched old control forests that had never been clear-cut. The treatment stands had significantly fewer species of liverworts and of the substrate-based species subgroup "wood or bark", and the six most negatively affected species were liverworts more or less specialized to this substrate. The only significant recovery recorded over the 15 years was for the "rocks or boulders" subgroup in upland stands, probably related to a shadier and moister climate resulting from canopy development. During the inter-survey period, some of the upland treatment stands were thinned. All disfavored subgroups recovered less in thinned than in not thinned upland stands, most likely as a result of a return to lighter and drier microclimates and direct mechanical disturbance. The incomplete and slow recovery halfway into the forestry rotation period calls for action. Adaptation of thinning for conservation has rarely been implemented in boreal forest management, but has a large potential. To facilitate re-colonization by disfavored liverworts and mosses growing on wood or bark and/or under shaded and moist conditions, I suggest retention of unlogged patches during thinning and addition of coarse deadwood on the ground in these patches. Such measures would also favor re-colonization of other late-successional species.

  • 306.
    Dynesius, Mats
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gibb, Heloise
    Department of Zoology, La Trobe University, Melbourne, Australia.
    Hjältén, Joakim
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Surface covering of downed logs: Drivers of a neglected process in dead wood ecology2010In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 10, p. e13237-Article in journal (Refereed)
    Abstract [en]

    Many species use coarse woody debris (CWD) and are disadvantaged by the forestry-induced loss of this resource. A neglected process affecting CWD is the covering of the surfaces of downed logs caused by sinking into the ground (increasing soil contact, mostly covering the underside of the log), and dense overgrowth by ground vegetation. Such cover is likely to profoundly influence the quality and accessibility of CWD for wood-inhabiting organisms, but the factors affecting covering are largely unknown. In a five-year experiment we determined predictors of covering rate of fresh logs in boreal forests and clear-cuts. Logs with branches were little covered because they had low longitudinal ground contact. For branchless logs, longitudinal ground contact was most strongly related to estimated peat depth (positive relation). The strongest predictor for total cover of branchless logs was longitudinal ground contact. To evaluate the effect on cover of factors other than longitudinal ground contact, we separately analyzed data from only those log sections that were in contact with the ground. Four factors were prominent predictors of percentage cover of such log sections: estimated peat depth, canopy shade (both increasing cover), potential solar radiation calculated from slope and slope aspect, and diameter of the log (both reducing cover). Peat increased cover directly through its low resistance, which allowed logs to sink and soil contact to increase. High moisture and low temperatures in pole-ward facing slopes and under a canopy favor peat formation through lowered decomposition and enhanced growth of peat-forming mosses, which also proved to rapidly overgrow logs. We found that in some boreal forests, peat and fast-growing mosses can rapidly cover logs lying on the ground. When actively introducing CWD for conservation purposes, we recommend that such rapid covering is avoided, thereby most likely improving the CWD’s longevity as habitat for many species.

  • 307.
    Dynesius, Mats
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Stockholms universitet, Botaniska institutionen.
    Hylander, Kristoffer
    Stockholms universitet, Botaniska institutionen.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    High resilience of bryophyte assemblages in streamside compared to upland forests2009In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, no 4, p. 1042-1054Article in journal (Refereed)
    Abstract [en]

    Landscape heterogeneity causes spatial variation in disturbance regimes and resilience. We asked whether the resilience of bryophyte (liverwort and moss) assemblages to clear-cutting differs between streamside and upland boreal forests in northern Sweden. We hypothesized that bryophyte survival and recolonization rates are higher in streamside areas, thus raising resilience. Conversely, disturbance-intolerant but also invading species should be more frequent here, potentially reducing resilience. In each of 18 sites, we compared two 0.1-ha plots (one streamside and one upland) located in old forest that had never been clear-cut with two matching plots in young stands established after clear-cutting of old forests 30-50 years earlier. We used the magnitude of the difference in assemblages between old and young stands as a measure of change and, therefore, resilience (large difference implying low resilience). Species assemblages were more resilient in streamside than in upland forests. Species composition changed significantly in upland but not in streamside forests. Reductions in species richness were more pronounced in upland forests for total richness and for eight subgroups of species. Two results indicated lower survival/recolonization in upland forests: (1) species had a stronger association with old stands in upland areas, and (2) among species present in both the old streamside and old upland plot in a site, fewer appeared in the young upland than in the corresponding streamside plot. Simultaneously, a higher proportion of species invaded streamside areas; 40 of the 262 species encountered in streamside forests increased their occupancy by two or more sites compared to only two of 134 species in uplands. We suggest that in boreal forests spatial variation in resilience of assemblages of forest organisms intolerant of canopy removal is related to factors governed mainly by topography. More generally, we argue that landscape-scale variation in resilience of assemblages is influenced by spatial variation in (1) stress and resource availability, (2) number of  disturbance intolerant species, and (3) magnitude of environmental changes brought about by a disturbance with a specific intensity. We also suggest that rapid recovery in the short term does not necessarily imply higher long-term ability to return to the pre-disturbance state.

  • 308. Ecke, Frauke
    et al.
    Berglund, Åsa M. M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rodushkin, Ilia
    Engström, Emma
    Pallavicin, Nicola
    Sörlin, Dieke
    Nyholm, Erik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hörnfeldt, Birger
    Seasonal shift of diet in bank voles explains trophic fate of anthropogenic osmium?2018In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 624, p. 1634-1639Article in journal (Refereed)
    Abstract [en]

    Diet shifts are common in mammals and birds, but little is known about how such shifts along the food web affect contaminant exposure. Voles are staple food for many mammalian and avian predators. There is therefore a risk of transfer of contaminants accumulated in voles within the food chain. Osmium is one of the rarest earth elements with osmium tetroxide (OsO4 ) as the most toxic vapor-phase airborne contaminant. Anthropogenic OsO4 accumulates in fruticose lichens that are important winter food of bank voles (Myodes glareolus). Here, we test if a) anthropogenic osmium accumulates in bank voles in winter, and b) accumulation rates and concentrations are lower in autumn when the species is mainly herbivorous. Our study, performed in a boreal forest impacted by anthropogenic osmium, supported the hypotheses for all studied tissues (kidney, liver, lung, muscle and spleen) in 50 studied bank voles. In autumn, osmium concentrations in bank voles were even partly similar to those in the graminivorous field vole (Microtus agrestis: n =3D 14). In autumn but not in late winter/early spring, osmium concentrations were generally negatively correlated with body weight and root length of the first mandible molar, i.e. proxies of bank vole age. Identified negative correlations between organ-to-body weight ratios and osmium concentrations in late winter/early spring indicate intoxication. Our results suggest unequal accumulation risk for predators feeding on different cohorts of bank voles. 

  • 309. Ecke, Frauke
    et al.
    Christensen, Pernilla
    Rentz, Ralf
    Nilsson, Mats
    Sandström, Per
    Hörnfeldt, Birger
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Vindelfjällens forskningsstation, Ammarnäs, Sweden; Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden .
    Landscape structure and the long-term decline of cyclic grey-sided voles in Fennoscandia2010In: Landscape Ecology, ISSN 0921-2973, E-ISSN 1572-9761, Vol. 25, no 4, p. 551-560Article in journal (Refereed)
    Abstract [en]

    Changes in forest landscape structure have been suggested as a likely contributing factor behind the long-term decline in the numbers of cyclic grey-sided voles (Clethrionomys rufocanus) in northern Fennoscandian lowland regions in contrast to mountain regions due to the absence of forest management in the mountains. This study, for the first time, formally explored landscape structure in 29 lowland (LF) and 14 mountain forest (MF) landscapes (each 2.5 x 2.5 km) in northern Sweden, and related the results to the cumulated spring trapping index of the grey-sided vole in 2002-2006. The grey-sided vole showed striking contrasts in dynamics close in space and time. The MF landscapes were characterized by larger patches and less fragmentation of preferred forest types. The grey-sided vole was trapped in all of 14 analyzed MF landscapes but only in three out of 29 of the LF landscapes. MF and LF landscapes with grey-sided vole occurrence were characterized by similar focal forest patch size (mean 357 ha, minimum 82 ha and mean 360 ha, minimum 79 ha, respectively). In contrast, these MF compared to the LF landscapes were characterized by larger patches of preferred forest types and less fragmented preferred forest types and by a lower proportion of clear-cut areas. The present results suggest that landscape structure is important for the abundance of grey-sided voles in both regions. However, in the mountains the change from more or less seasonal dynamics to high-amplitude cycles between the mid 1990s and 2000s cannot be explained by changes in landscape structure.

  • 310. Ecke, Frauke
    et al.
    Singh, Navinder J.
    Arnemo, Jon M.
    Bignert, Anders
    Helander, Björn
    Berglund, Åsa M. M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Borg, Hans
    Bröjer, Caroline
    Holm, Karin
    Lanzone, Michael
    Miller, Tricia
    Nordström, Åke
    Räikkönen, Jannikke
    Rodushkin, Ilia
    Ågren, Erik
    Hörnfeldt, Birger
    Sublethal Lead Exposure Alters Movement Behavior in Free-Ranging Golden Eagles2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 10, p. 5729-5736Article in journal (Refereed)
    Abstract [en]

    Lead poisoning of animals due to ingestion of fragments from lead-based ammunition in carcasses and offal of shot wildlife is acknowledged globally and raises great concerns about potential behavioral effects leading to increased mortality risks. Lead levels in blood were correlated with progress of the moose hunting season. Based on analyses of tracking data, we found that even sublethal lead concentrations in blood (25 ppb, wet weight), can likely negatively affect movement behavior (flight height and movement rate) of free ranging scavenging Golden Eagles (Aquila chrysaetos). Lead levels in liver of recovered post-mortem analyzed eagles suggested that sublethal exposure increases the risk of mortality in eagles. Such adverse effects on animals are probably common worldwide and across species, where game hunting with lead-based ammunition is widespread. Our study highlights lead exposure as a considerably more serious threat to wildlife conservation than previously realized and suggests implementation of bans of lead ammunition for hunting.

  • 311. Eeva, Tapio
    et al.
    Rainio, Miia
    Berglund, Åsa
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kanerva, Mirella
    Stauffer, Janina
    Stoewe, Mareike
    Ruuskanen, Suvi
    Experimental manipulation of dietary lead levels in great tit nestlings: limited effects on growth, physiology and survival2014In: Ecotoxicology, ISSN 0963-9292, E-ISSN 1573-3017, Vol. 23, no 5, p. 914-928Article in journal (Refereed)
    Abstract [en]

    We manipulated dietary lead (Pb) levels of nestlings in wild populations of the great tit (Parus major L) to find out if environmentally relevant Pb levels would affect some physiological biomarkers (haematocrit [HT], fecal corticosterone metabolites [CORT], heat shock proteins [HSPs], erythrocyte delta-aminolevulinic acid dehydratase activity [ALAd]), growth (body mass, wing length), phenotype (plumage coloration) or survival of nestlings. The responses to three experimental manipulation (control, low and high: 0, 1 and 4 mu g/g body mass/day) are compared with those in a P. major population breeding in the vicinity of a heavy metal source, a copper smelter. Our Pb supplementation was successful in raising the fecal concentrations to the levels found in polluted environments (high: 8.0 mu g/g d.w.). Despite relatively high range of exposure levels we found only few effects on growth rates or physiology. The lack of blood ALAd inhibition suggests that the circulating Pb levels were generally below the toxic level despite that marked accumulation of Pb in femur (high: 27.8 mu g/g d.w.) was observed. Instead, birds in the metal polluted environment around the smelter showed decreased growth rates, lower HT, higher CORT, less colorful plumage and lower survival probabilities than any of the Pb treated groups. These effects are likely related to decreased food quality/quantity for these insectivorous birds at the smelter site. In general, the responses of nestlings to metal exposure and/or associated resource limitation were not gender specific. One of the stress proteins (HSP60), however, was more strongly induced in Pb exposed males and further studies are needed to explore if this was due to higher accumulation of Pb or higher sensitivity of males. In all, our results emphasize the importance of secondary pollution effects (e.g. via food chain disruption) on reproductive output of birds.

  • 312. Effenberger, M.
    et al.
    Engel, J.
    Diehl, S.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Matthaei, C. D.
    Disturbance history influences the distribution of stream invertebrates by altering microhabitat parameters: a field experiment2008In: Freshwater Biology, Vol. 53, no 5, p. 996-1011Article in journal (Refereed)
    Abstract [en]

    1. We investigated the effects of local disturbance history and several biotic and abiotic habitat parameters on the microdistribution of benthic invertebrates after an experimental disturbance in a flood-prone German stream. 2. Bed movement patterns during a moderate flood were simulated by scouring and filling stream bed patches (area 0.49 m(2)) to a depth of 15-20 cm. Invertebrates were investigated using ceramic tiles as standardized substrata. After 1, 8, 22, 29, 36 and 50 days, we sampled one tile from each of 16 replicates of three bed stability treatments (scour, fill and stable controls). For each tile, we also determined water depth, near-bed current velocity, the grain size of the substratum beneath the tile, epilithic algal biomass and standing stock of particulate organic matter (POM). 3. Shortly after disturbance, total invertebrate density, taxon richness and density of the common taxa Baetis spp. and Chironomidae were highest in stable patches. Several weeks after disturbance, by contrast, Baetis spp. and Hydropsychidae were most common in fill and Leuctra spp. in scour patches. The black fly Simulium spp. was most abundant in fill patches from the first day onwards. Community evenness was highest in scour patches during the entire study. 4. Local disturbance history also influenced algal biomass and POM standing stock at the beginning of the experiment, and water depth, current velocity and substratum grain size throughout the experiment. Scouring mainly exposed finer substrata and caused local depressions in the stream bed characterized by slower near-bed current velocity. Algal biomass was higher in stable and scour patches and POM was highest in scour patches. In turn, all five common invertebrate taxa were frequently correlated with one or two of these habitat parameters. 5. Our results suggest that several 'direct' initial effects of local disturbance history on the invertebrates were subsequently replaced by 'indirect' effects of disturbance history (via disturbance-induced changes in habitat parameters such as current velocity or food).

  • 313.
    Egelkraut, Dagmar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Aronsson, Kjell-Åke
    Ájtte, Swedish Mountain and Sami Museum, Jokkmokk, Sweden.
    Allard, Anna
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Åkerholm, Marianne
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Stark, Sari
    Arctic Centre, University of Lapland, Rovaniemi, Finland.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Multiple feedbacks contribute to a centennial legacy of reindeer on tundra vegetation2018In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, no 8, p. 1545-1563Article in journal (Refereed)
    Abstract [en]

    Historical contingency is the impact of past events, like the timing and order of species arrival, on community assembly, and can sometimes result in alternative stable states of ecological communities. Large herbivores, wild and domestic, can cause profound changes in the structure and functioning of plant communities and therefore probably influence historical contingency; however, little empirical data on the stability of such shifts or subsequent drivers of stability are available. We studied the centennial legacy of reindeer (Rangifer tarandus) pressure on arctic tundra vegetation by considering historical milking grounds (HMGs): graminoid- and forb-dominated patches amid shrub-dominated tundra, formed by historical Sami reindeer herding practices that ended approximately 100 years ago. Our results show that the core areas of all studied HMGs remained strikingly stable, being hardly invaded by surrounding shrubs. Soil nitrogen concentrations were comparable to heavily grazed areas. However, the HMGs are slowly being reinvaded by vegetative growth of shrubs at the edges, and the rate of ingrowth increased with higher mineral N availability. Furthermore, our data indicate that several biotic feedbacks contribute to the stability of the HMGs: increased nutrient turnover supporting herbaceous vegetation, strong interspecific competition preventing invasion and herbivore damage to invading shrubs. In particular, voles and lemmings appear to be important, selectively damaging shrubs in the HMGs. We concluded that HMGs provide clear evidence for historical contingency of herbivore effects in arctic ecosystems. We showed that several biotic feedbacks can contribute to subsequent vegetation stability, but their relative importance will vary in time and space.

  • 314.
    Egelkraut, Dagmar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University.
    Barthelemy, Hélène
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Reindeer trampling causes vegetation changes in tundra heathlands: results from a simulation experimentManuscript (preprint) (Other academic)
  • 315.
    Egelkraut, Dagmar D.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Long-lasting ecological legacies of reindeer on tundra vegetation2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reindeer can have strong effects on the plant species composition and functioning of tundra ecosystems, and often promote a transition towards a graminoid-dominated vegetation type. As a result, they influence many ecological processes, such as nutrient dynamics, soil biotic composition and functioning, and carbon storage. Several studies suggest that the effect of reindeer on vegetation may follow predictable patterns and could induce an alternative stable vegetation state. However, little empirical data on the long-term stability of reindeer effects on vegetation exist, as it is inherently challenging to study these ecological processes experimentally on a sufficiently long timescale. The main objective of this thesis was therefore to gain a better understanding of the long-term ecological processes following reindeer-induced vegetation shifts.

    In order to gain a more mechanistic insight in what initially drives this transition, I used a field-based grazing simulation experiment in which I separated defoliation, trampling, moss removal and the addition of feces. This allowed me to test the relative contribution of reindeer-related activities to initiating the shift from moss and heath- dominated tundra towards a graminoid-dominated vegetation state. Additionally, I studied the long-term ecological stability following such a vegetation shift. I did this by addressing historical milking grounds (HMGs): sites where high reindeer concentrations associated with historical traditional reindeer herding practices induced a vegetation transition from shrubs towards graminoids several centuries earlier, but which were abandoned a century ago. Studying HMGs allowed me to address: 1. The potential stability of reindeer-induced vegetation shifts; 2. The ecological mechanisms contributing to the long-term stability of these vegetation shifts; and 3. How such long-lasting vegetation changes influence soil carbon- and nutrient cycling.

    I found that trampling by reindeer is an important mechanism by which reindeer cause vegetation change. Addressing HMGs further revealed that this vegetation change can be hightly persistent, as the studied HMGs showed only a low encroachment at the surrounding borders in the last 50 years. The vegetation in the core areas of all studied HMGs had remained strikingly stable, and were hardly invaded by surrounding shrubs. Interestingly, soil nutrient concentrations and microbial activities were still different from the surrounding area as well, and even comparable to actively grazed areas. Even after many centuries of changed vegetation composition and soil processes, there was no difference in total carbon sequestration. This suggests that the environmental conditions for microbial decomposition were more important than vegetation composition for the soil carbon stocks, in our study site.

    After studying the contemporary habitat use of HMGs by reindeer and other herbivores, investigating the potential plant-soil feedbacks mechanisms and detailed soil analyses, I concluded that several ecological mechanisms contribute to the long-term stability of HMGs: first, the altered soil biotic and abiotic conditions appear to have a stronger advantage for HMG vegetation than for the surrounding tundra vegetation. Furthermore, I found a clear browsing preference of small rodents on single shrubs proliferating in HMGs, causing a strong limitation on shrub expansion. Moreover, the dense established sward of graminoids likely poses a strong direct competition for space and nutrients, hindering seedling establishment. Finally, I conclude that HMGs are highly stable on relevant ecological timescales, and propose how the concepts of historical contingency and ASS can be applied to understand stability of these reindeer-induced vegetation transitions.

  • 316.
    Egelkraut, Dagmar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kardol, Paul
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
    De Long, Jonathan R.
    Department of Terrestrial Ecology, Netherlands Institute of Ecology, Wageningen, The Netherlands.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The role of plant-soil feedbacks in stabilizing a reindeer-induced vegetation shift in subarctic tundra2018In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 32, no 8, p. 1959-1971Article in journal (Refereed)
    Abstract [en]

    1. Herbivory can drive vegetation into different states of productivity and community composition, and these changes may be stable over time due to historical contingency effects. Interactions with abiotic and biotic soil components can contribute to such long-term legacies in plant communities through stabilizing positive feedbacks.

    2. We studied the role of plant-soil feedbacks in maintaining vegetation changes caused by historical (similar to 1350-1900 AD) reindeer herding in northern Sweden. These historical milking grounds (HMGs) consist of meadow plant communities formed in naturally nutrient-poor heath or naturally nutrient-rich shrub-dominated vegetation and are still clearly visible in the landscape, a century after active use ceased.

    3. We selected two phytometer species: the forb Potentilla crantzii as representative of HMG vegetation, and the dwarf shrub Betula nana, as representative of control vegetation. We grew both species under glasshouse conditions on soils derived from replicated HMG and paired control plots, using live soils and sterilized (-radiation)-inoculated soils, to separate between biotic and abiotic soil effects.

    4. A net negative plant-soil feedback for B.nana biomass in its home (i.e., control) soil and a net positive feedback for P.crantzii in its home (i.e., HMG) soil in heath habitat was partly driven by the soil biotic community. However, abiotic differences in mineral nitrogen (N) concentrations between control and HMG soils were a stronger driver of differences in plant growth. Positive feedbacks maintaining a high mineral nutrient availability are thus important, especially in nutrient-poor habitats.

    5. The positive plant responses to higher soil mineral N concentrations, combined with positive biotic plant-soil feedbacks, might shift the competitive balance in favour of typical HMG plant species, thereby contributing to stability of HMG plant communities. Our data indicate that herbivore-driven changes in the interactions between plants and both biotic and abiotic components of the soil persist over long temporal scales.

  • 317. Ehmke, Mariah D
    et al.
    Shogren, Jason F
    Umeå University, Faculty of Social Sciences, Department of Economics. Stroock Professor, Department of Economics and Finance, University of Wyoming, 1000 University Ave, Dept 3985, Laramie, WY 82071, USA.
    Experimental methods for environment and development economics2009In: Environment and Development Economics, ISSN 1355-770X, E-ISSN 1469-4395, Vol. 14, no 4, p. 419-456Article, review/survey (Refereed)
    Abstract [en]

    Many poor countries remain trapped in a cycle of poverty and environmental degradation. Understanding how people react to existing and proposed solutions most likely can be improved using the methods of experimental economics. Experiments provide researchers a method to test theory, look for patterns of behavior, testbed economic institutions and incentives, and to educate people. Herein we explore how experimental economics has been used and could be used to help guide decision making to increase prosperity without overexploiting the resource base and environmental assets needed for basic survival.

  • 318.
    Eilertsen, Lill
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Presence of Hydnellum species on pine heaths2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this study was to assess whether the age, the circumference and the density of trees and stumps in forests affect the occurrence of stipitate hydnoid fungi in the genus Hydnellum. This was done by surveying sporocarps of Hydnellum species in 19 forest stands of potential different age and forest characteristics on a low productive pine heath in northern Sweden. All other fungal species that was present in the forest stands were also noted. The estimated mean age of the trees in the studied forest stands varied between 25 and 144 years. There was a positive correlation between the number of Hydnellum sporocarps, as well as between the number of fungal species observed, and the estimated age and the mean circumference of the trees in the stands. The number of sporocarps of Hydnellum species was also positively correlated with the total number of fungal species found. In total, 54 different species of fungi was found and several threatened fungal species other than Hydnellum were found in the older stands. The lower number of Hydnellum and other fungi in younger stands may be due to these stands being more affected by logging. More thorough studies are needed to evaluate the status and ecological requirements of these fungi to prevent them from further decline.

  • 319. Ejsmond, M. J.
    et al.
    Blackburn, N.
    Fridolfsson, E.
    Haecky, P.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Casini, M.
    Belgrano, A.
    Hylander, S.
    Modeling vitamin B1 transfer to consumers in the aquatic food web2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 10045Article in journal (Refereed)
    Abstract [en]

    Vitamin B-1 is an essential exogenous micronutrient for animals. Mass death and reproductive failure in top aquatic consumers caused by vitamin B-1 deficiency is an emerging conservation issue in Northern hemisphere aquatic ecosystems. We present for the first time a model that identifies conditions responsible for the constrained flow of vitamin B-1 from unicellular organisms to planktivorous fishes. The flow of vitamin B-1 through the food web is constrained under anthropogenic pressures of increased nutrient input and, driven by climatic change, increased light attenuation by dissolved substances transported to marine coastal systems. Fishing pressure on piscivorous fish, through increased abundance of planktivorous fish that overexploit mesozooplankton, may further constrain vitamin B-1 flow from producers to consumers. We also found that key ecological contributors to the constrained flow of vitamin B-1 are a low mesozooplankton biomass, picoalgae prevailing among primary producers and low fluctuations of population numbers of planktonic organisms.

  • 320.
    Ekerholm, Per
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Population dynamics of tundra-living grey-sided voles2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the dynamics of tundra living voles with emphasis on the most common one, the grey-sided vole (Clethrionomys rufocanus). The tundra area chosen for the study was Finnmarksvidda, a vast flatland in northernmost Norway. All small mammal herbivores in the area showed dramatic fluctuations, and field experiment were conducted in order to elucidate these density fluctuations. The specific subjects addressed included: 1/ Temporal and spatial appearance of density fluctuations of voles and lemmings in the area, 2/ The generality of the density patterns observed, 3/ The impact of predation by vole predators during summertime, 4/ The impact of grey-sided vole grazing on food plants of different preference in a predator free environment, in the presence and absence of extra food, and 5/ The impact of food availability on density and demography of grey-sided voles in a predator free environment.

    The results achieved showed that voles in the slope and lowland had cyclic density fluctuations with 5 years duration. The cycles consisted of four phases: an increase phase, a peak phase, a decline phase and a crash phase. In the unproductive lowland and on the moderately productive slope, small pockets of productive habitats seemed to work as “triggers” for the cycles. The lemming fluctuations in the upper plateau (separated from the slope by a steep zone of boulders) differed markedly from the vole patterns in the lowland.

    Only two lemming peaks were recorded in twenty years. Both peaks had very short increase phases, a knife-sharppeak phase and no decline phase before the crash. A comparison between our results and lemming and vole populations from two other areas in Fennoscandia revealed the same difference in fluctuation pattern between lemmings and voles as seen in our area. This results suggests that lemmings in barren tundra highlands and voles in slightly more productive tundra lowlands are regulated by different mechanisms.

    The exclusion of vole predators from vole populations during summertime led to increase in overall vole density. Densities of the clumsy field vole (Microtus agrestis) and juveniles of all species showed the strongest positive effects of the exclusion.

    An experiment analysing the effects of food availability was conducted in islands in a large lake where grey-sided voles were introduced to predator free islands . Supplemental food was given to the voles in two unproductive, and two productive islands. Two unproductive and two productive islands were used as reference islands. The density of voles and the vole weight were higher in both the islands with supplemental food and those with high natural productivity. Increased vole density did not significantly increase grazing damage to plants. The cyclic density pattern of the voles in the nearby mainland (that harboured resident vole specialist predators as stoat and weasel) showed little resemblance to the seasonal fluctuations found in the islands (devoid of resident vole specialist predators). This result suggested that predation by stoat and weasel on grey-sided vole populations may cause the cyclic vole fluctuations seen in the area.

  • 321. Eklov, P.
    et al.
    Diehl, S.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    PISCIVORE EFFICIENCY AND REFUGING PREY - THE IMPORTANCE OF PREDATOR SEARCH MODE1994In: Oecologia, Vol. 98, no 3-4, p. 344-353Article in journal (Refereed)
    Abstract [en]

    In predator-prey interactions, the efficiency of the predator is dependent on characteristics of both the predator and the prey, as well as the structure of the environment. In a field enclosure experiment, we tested the effects of a prey refuge on predator search mode, predator efficiency and prey behaviour. Replicated enclosures containing young of the year (0+) and 1-year-old (1+) perch were stocked with 3 differentially sized individuals of either of 2 piscivorous species, perch (Perca fluviatilis), pike (Esox lucius), or no piscivorous predators. Each enclosure contained an open predator area with three small vegetation patches, and a vegetated absolute refuge for the prey. We quantified the behaviour of the predators and the prey simultaneously, and at the end of the experiment the growth of the predators and the mortality and habitat use of the prey were estimated. The activity mode of both predator species was stationary. Perch stayed in pairs in the vegetation patches whereas pike remained solitary and occupied the corners of the enclosure. The largest pike individuals stayed closest to the prey refuge whereas the smallest individuals stayed farthest away from the prey refuge, indicating size-dependent interference among pike. Both size classes of prey showed stronger behavioural responses to pike than to perch with respect to refuge use, distance from refuge and distance to the nearest predator. Prey mortality was higher in the presence of pike than in the presence of perch. Predators decreased in body mass in all treatments, and perch showed a relatively stronger decrease in body mass than pike during the experiment. Growth differences of perch and pike, and mortality differences of prey caused by predation, can be explained by predator morphology, predator attack efficiency and social versus interference behaviour of the predators. These considerations suggest that pike are more efficient piscivores around prey refuges such as the littoral zones of lakes, whereas perch have previously been observed to be more efficient in open areas, such as in the pelagic zones of lakes.

  • 322.
    Eklöv, Peter
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Effects of behavioural flexibility and habitat complexity on predator-prey interactions in fish communities1995Doctoral thesis, comprehensive summary (Other academic)
  • 323. Eklöv, Peter
    et al.
    Svanbäck, Richard
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Predation favors adaptive morphological variation in perch populationsManuscript (Other academic)
  • 324.
    Elbakidze, M
    et al.
    Swedish University of Agricultural Sciences.
    Angelstam, PK
    Swedish University of Agricultural Sciences.
    Sandström, Camilla
    Umeå University.
    Axelsson, R
    Swedish University of Agricultural Sciences.
    Multi-stakeholder collaboration in Russian and Swedish model forest initiatives: adaptive governance toward sustainable forest management?2010In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 15, no 2, article id 14Article in journal (Refereed)
    Abstract [en]

    Building the adaptive capacity of interlinked social and ecological systems is assumed to improve implementation of sustainable forest management (SFM) policies. One mechanism is collaborative learning by continuous evaluation, communication, and transdisciplinary knowledge production. The Model Forest (MF) concept, developed in Canada, is intended to encourage all dimensions of sustainable development through collaboration among stakeholders of forest resources in a geographical area. Because the MF approach encompasses both social and ecological systems, it can be seen as a process aimed at improving adaptive capacity to deal with uncertainty and change. We analyzed multi-stakeholder approaches used in four MF initiatives representing social–ecological systems with different governance legacies and economic histories in the northwest of the Russian Federation (Komi MF and Pskov MF) and in Sweden (Vilhelmina MF and the Foundation Säfsen Forests in the Bergslagen region). To describe the motivations behind development of the initiative and the governance systems, we used qualitative open-ended interviews and analyzed reports and official documents. The initial driving forces for establishing new local governance arrangements were different in all four cases. All MFs were characterized by multi-level and multi-sector collaboration. However, the distribution of power among stakeholders ranged from clearly top down in the Russian Federation to largely bottom up in Sweden. All MF initiatives shared three main challenges: (a) to develop governance arrangements that include representative actors and stakeholders, (b) to combine top-down and bottom-up approaches to governance, and (c) to coordinate different sectors’ modes of landscape governance. We conclude that, in principle, the MF concept is a promising approach to multi-stakeholder collaboration. However, to understand the local and regional dimensions of sustainability, and the level of adaptability of such multi-stakeholder collaboration initiatives, empirical studies of outcomes are needed. To assess the adaptive capacity, the states and trends of economic, ecological, social, and cultural dimensions in actual landscapes need to be linked to how the multi-stakeholder collaboration develops and performs over the long term.

  • 325.
    Elveland, Jan
    Umeå University, Faculty of Science and Technology.
    Myrar på Storön vid Norrbottenskusten1976Doctoral thesis, monograph (Other academic)
    Abstract [en]

    ELVELAND, J. 1976. Coastal mires on the Storön peninsula, Norrbotten, N Sweden. Wahlenbergia 3. 274 pp. (map + 1 fig. in end pocket). Umeå.Vegetation, flora and habitat conditions of mires on and above the seashore have been studied in an eutrophic coastal area (Storön) in N Sweden. Here the rate of land uplift is almost 1 m per century and vegetational dynamics are rather intense in the younger mires, especially in the seashore fens recently "born from the sea" (primary mire formation).The mire vegetation is dealt with in three main groups: seashore fens, fens above the seashore and bog vegetation. The plant communities have been classified on a basis of their physiognomically dominant species. "Sphagnum fuscum islets" (often called "miniature raised bogs" or "miniature bogs") in the rich fens form the predominant type of bog vegetation. In the present paper the main emphasis has been laid on the rich fens above the seashore.Several vegetational gradients are dealt with, i. a. rich fen-poor fen, mire margin-mire expanse and the complex gradient mud-bottom/carpet/magnocaricetum/ lawn/hummock. Both small-scale and large-scale successions are discussed and a floristic list (vascular plants, bryophytes and lichens) with ecological annotations is presented.Extensive field measurements of pH and electrolytic conductivity of mire waters have been made. The pH, ash content, SÌO2r s r P#• C and N, total content and exchangeable fractions of Na, K, Mg, Ca, Mn and Fe have been determined at different depths for various kinds of peat. The chemistry of lagoon and lake sediments have also been studied. The vertical gradients shown by the chemical parameters are of special interest regarding the Sphagnum fuscum islets. The surface peats of the islets are "functionally ombrotrophic", while from a depth of ca. 30 cm and downwards the chemical characteristics are those of a rich fen peat.Historical and present-day mire utilization is discussed, especially hay-making and cattle grazing.

  • 326.
    Enbom, Magnus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Natur och naturvägledning vintertid längs sträckan Abisko-Nikkaluokta2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 327. Engel, Fabian
    et al.
    Farrell, Kaitlin J.
    McCullough, Ian M.
    Scordo, Facundo
    Denfeld, Blaize A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dugan, Hilary A.
    de Eyto, Elvira
    Hanson, Paul C.
    McClure, Ryan P.
    Nöges, Peeter
    Nöges, Tiina
    Ryder, Elizabeth
    Weathers, Kathleen C.
    Weyhenmeyer, Gesa A.
    A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters2018In: The Science of Nature: Naturwissenschaften, ISSN 0028-1042, E-ISSN 1432-1904, Vol. 105, article id 25Article in journal (Refereed)
    Abstract [en]

    The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of 0.70(-0.31)(+0.27) 1.52(-0.90)(+1.09) Pg C yr(-1) depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.

  • 328.
    Englund, Göran
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Competition in caddis larvae1992Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with behavioural strategies used by caddis larvae in pairwise contests and when selecting microhabitats. Effects of caddis larvae on survival and habitat selection of other insect taxa have also been studied.

    The behaviours used by Arctopsyche ladogensis larvae fighting for nets, and Agrypnia pagetana larvae fighting for cases, agreed well with predictions from the sequential assessment game, which is an ESS model of animal fighting behaviour.

    Establishment by net-spinning Hydropsyche siltalai larvae on artificial substrates was highest at intermediate densities of residents. Emigration/mortality was density independent, and it was higher at a poor site (low food availability) than at a rich site. Establishment was unaffected by site quality. Growth was density dependent because larvae in upstream positions reduced both current velocity and concentration of food particles for larvae in downstream positions.

    A field experiment involved manipulations of the density of H. siltalai larvae and their nets in a lake outlet stream. H. siltalai larvae affected all abundant taxa, but the mechanism involved varied between taxa. Rhyacophila nubila (Trichoptera) and chironomid larvae benefited from the presence of H. siltalai nets. Negative effects on nymphs of the mayfly Ephemerella ignita were due to predation by H. siltalai larvae, while a combination of predation and increased emigration in response to nets depressed densities of Simulium truncatum blackfly larvae.

  • 329.
    Englund, Göran
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Eriksson, Håkan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Mats B.
    The birth and death of lakes on young landscapes2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 7Article in journal (Refereed)
    Abstract [en]

    Ongoing land uplift caused by postglacial isostatic rebound creates strong landscape-age gradients alongside the Gulf of Bothnia, northern Scandinavia. Lakes are continuously generated on this dynamic landscape as the uplift isolates bays from sea inundation. However, concomitant with this process older lakes are lost as the basins are filled with sediments, creating a continuum of lake ages on the landscape. We studied the lake size and depth distributions and lake densities, along an age gradient covering 0-4500 years. Map data on the density, area, and elevation of lakes were combined with field-based measurements of maximum basin depth. We find that young lake populations are densely distributed and dominated by small and shallow lakes. Over time, small and shallow lakes are lost by complete sediment filling, resulting in lower lake density and a shift in size and depth distributions towards larger, deeper lakes. Since lake filling is a universal process, we propose that these findings can be generalized to other gradients in landscape age.

  • 330.
    Englund, Göran
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sjödin, Henrik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bonsall, Michael
    Oxford University.
    Cianelli, Lorenzo
    Oregon State University.
    Frank, Kenneth
    Bedford Institute of Oceanography.
    Heino, Mikko
    University of Bergen.
    Janssen, Arne
    University of Amsterdam.
    Leonardsson, Kjell
    Swedish University of Agricultural Science.
    van der Meer, Jaap
    Royal Netherlands Institute for Sea Research.
    Nachman, Gösta
    Copenhagen University.
    Yu, Jun
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Density dependence induced by the spatial covariance between predators and preyManuscript (preprint) (Other academic)
  • 331.
    Englund, Göran
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Öhlund, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hein, Catherine L
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Temperature dependence of the functional response2011In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 14, no 9, p. 914-21Article in journal (Refereed)
    Abstract [en]

    The Arrhenius equation has emerged as the favoured model for describing the temperature dependence of consumption in predator-prey models. To examine the relevance of this equation, we undertook a meta-analysis of published relationships between functional response parameters and temperature. We show that, when plotted in lin-log space, temperature dependence of both attack rate and maximal ingestion rate exhibits a hump-shaped relationship and not a linear one as predicted by the Arrhenius equation. The relationship remains significantly downward concave even when data from temperatures above the peak of the hump are discarded. Temperature dependence is stronger for attack rate than for maximal ingestion rate, but the thermal optima are not different. We conclude that the use of the Arrhenius equation to describe consumption in predator-prey models requires the assumption that temperatures above thermal optima are unimportant for population and community dynamics, an assumption that is untenable given the available data.

  • 332.
    Engstedt, Olof
    Linnéuniversitetet, Institutionen för naturvetenskap, NV.
    Anadromous Pike in the Baltic Sea2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The pike (Esox lucius) is a major predator and top-down regulator in the Baltic Sea where it exists in two sympatric forms. One spawn in streams and rivers and the other one spawn in the sea. During the last decades, the habitats for both of these forms have developed in a negative way. In some freshwater systems, up to 90 % of the water areas have disappeared, mainly through drainage and straightening of watercourses for agricultural purposes. In the sea, reproduction habitats decrease due to construction of harbours and human activities that create disturbances. The perhaps largest single factor negatively affecting recruitment of pike in the sea is the eutrophication. Bottoms are overgrown with filamentous algae and shallow bays are covered with dense Phragmites belts decreasing the habitats suitable for spawning. Further on, a predator on egg and fish larvae, the three-spined stickleback (Gasterosteus aculeatus) has increased in abundance. It is difficult to restore and enhance pike production in the sea and probably the only economically viable alternative is to make restorations in freshwater. However, there is a limited knowledge about the freshwater spawning pike in the Baltic Sea. Thus in this thesis I, together with my coauthors, set out with an aim to increase the knowledge base regarding anadromous pike behaviour.

    We found that pike of natal freshwater origin were common in the Baltic Sea. Through Sr:Ca studies in otoliths, about 45 % of the pike were interpreted to be of freshwater origin. The majority of the pike had emigrated out of freshwater at a length below 6 cm. These results indicate that freshwater recruitment is successful, contrasting the vast areas available for spawning in the sea. This creates incitements that restoration measures in these watercourses could have a significant effect on the pike population in the Baltic Sea.

    Further, in four streams running out in the Baltic Sea, more than three thousand pike were marked to study spawning migration. About 30-40 % returned to the same river the subsequent year. Most of the pike used the lower parts of the stream for spawning. The homing of pike to a watercourse indicate that freshwater pike in the Baltic Sea consist of specific populations and this is crucial information when taking decisions on fish restoration measures.

    Three wetlands adjacent to streams were restored for pike production. The most successful restoration involved minimal digging, with flooded grasslands providing optimal conditions for spawning. The first spawning season after restoration increased the pike production hundredfold.

    In conclusion, the anadromous pike are numerous in the Baltic Sea. To compensate for the decline in pike populations in the sea, “pike-factories” created along the coastline are probably the most justifiable option.

  • 333.
    Engstedt, Olof
    et al.
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Engkvist, Roland
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Larsson, Per
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Elemental fingerprinting in otoliths reveals natal homing of anadromous Baltic Sea pike (Esox lucius L.)2014In: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 23, no 3, p. 313-321Article in journal (Refereed)
    Abstract [en]

    We examined the element pattern in the otoliths of a migratory fish species that inhabit the coastal areas in the brackish of the Baltic Sea. The northern pike (Esox lucius) show migratory behaviour, spawning in streams and rivers and foraging in the sea. We examined spawning migration in four nearby streams in the south-west part of the Baltic. Otolith analysis by microPIXE revealed unique elemental patterns (Sr, Zn, Br, Co and Mn) for the juveniles in each of the different streams. The strontium signal in the otolith of the juveniles was used as an indicator of freshwater origin and the time spent in the stream. Adult pike in their migrating spawning phase were caught in each of the streams. The elemental composition in otoliths in their freshwater phase (using juvenile pike in the streams as references) was determined. A principal component analysis showed that the elemental fingerprint during the freshwater phase several years back in time was similar for the adult fish and for juveniles inhabiting the stream today. The results indicated natal homing of the adults to a specific stream, a conclusion that was strengthened by the fact that marked fish returned to spawn over consecutive years. Anadromous pike in the Baltic Sea may thus be divided in subpopulations. The results of the study may have implications for fishery management, as pike in the Baltic Sea cannot be seen as homogenous population.

  • 334.
    Engström, Johanna
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Effects of restoration on riparian biodiversity in secondary channels of the Pite River.2005Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 335.
    Engström, Johanna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Roland
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Weber, Christine
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effects of river ice on riparian vegetation2011In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 56, no 6, p. 1095-1105Article in journal (Refereed)
    Abstract [en]

    1.  Many rivers and streams experience pronounced ice dynamics caused by the formation of anchor and frazil ice, leading to flooding and disturbance of riparian and aquatic communities.  The effects of dynamic ice conditions on riverine biota are little known.

    2.  We studied the formation of anchor ice in natural streams over 2 years, and assessed the effects of anchor ice on riparian vegetation by comparing sites with frequent or abundant and little or no anchor ice formation. We also studied the direct impact of ice on riparian plants by experimentally creating ice in the riparian zone over three winters, and by exposing plants of different life-forms to ‑18oC cold ice in the laboratory.

    3.  Riparian species richness per 1-m2 plot was higher at sites affected by anchor ice than at sites where anchor ice was absent or rare. Dominance was lower at anchor ice sites, suggesting that ice disturbance enhanced species richness. Species composition was more homogenous among plots at anchor ice sites. Experimentally creating riparian ice corroborated the comparative results, with species richness increasing in ice-treated plots compared to controls, irrespective of whether the sites showed natural anchor ice.

    4.  Because of human alterations of running waters, the natural effects of river ice on stream hydrology, geomorphology and ecology are little known.  Global warming in northern streams will lead to more dynamic ice conditions, offering new challenges for aquatic organisms and river management.  We expect that the results discussed here can stimulate new research, contributing to a better understanding of ecosystem function during winter.

  • 336.
    Enobile, Sylvanus
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Density-dependent development of size variation in larval perch (Perca fluviatilis)2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 337.
    Ericson, Lars
    Umeå University, Faculty of Science and Technology.
    The influence of voles and lemmings on the vegetation in a coniferous forest during a 4-year period in northern Sweden1977Doctoral thesis, monograph (Other academic)
  • 338.
    Ericson, Lars
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mueller, Warren J.
    Burdon, Jeremy J.
    28-year temporal sequence of epidemic dynamics in a natural rust-host plant metapopulation2017In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 105, no 3, p. 701-713Article in journal (Refereed)
    Abstract [en]

    1. A long-term study of disease dynamics caused by the rust Uromyces valerianae in 31 discrete populations of Valeriana salina provides a rare opportunity to explore extended temporal patterns in the epidemiology of a natural host-pathogen metapopulation. 2. Over a 28-year period, pathogen population dynamics varied across the metapopulation with disease incidence (presence/absence), prevalence (% plants infected) and severity (% leaf area covered by lesions) all showing strong population and year effects, indicative of heterogeneity among years and host populations in the suitability of conditions for the pathogen. 3. Disease incidence within individual host populations was significantly affected by host population size, disease prevalence the previous year and the proximity of neighbouring populations infected in the current year. After accounting for these variables there was still a marked temporal component with winter sea level having a significant effect; as did summer rainfall in the second part of the study period (1997-2011). 4. Disease prevalence was also effected by host population size and disease prevalence in the previous year. However, it was less affected by spatial aspects of disease spread than was disease incidence. Winter sea level and June rainfall significantly affected disease prevalence. 5. Assessment of disease impact on plant performance found strong variation in disease severity associated with the aspect and positioning of host populations. Plants growing in lower disease environments produced significantly more seeds than those growing in high disease sites. 6. Significant variation in reaction to infection by U. valerianae was detected among plants within four populations and between these different populations. 7. Synthesis. The epidemiology of Uromyces valerianae was highly influenced by host population size, previous disease and distance. After accounting for these factors, there was a clear temporal signal of change in disease incidence linked to winter sea level and summer rainfall. These patterns reinforce the importance of considering interactions in multiple populations over long periods of time in order to obtain a clear picture of the variability in disease-induced selection pressures across time and space. The behaviour of the pathogen fitted that predicted for a metapopulation with considerable asynchrony in epidemiological patterns among demes.

  • 339.
    Ericson, Martin
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Trädvegetation i västmanländska rikkärr och skötselförslag för framtiden2006Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 340.
    Eriksson, Amanda
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Water storage in the lichen genus Usnea in Sweden and Norway: Can morphological and water storage traits explain the distribution and ecology of epiphytic species?2015Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Lichens are poikilohydric and cannot control water uptake and loss, water relations could therefore impact their distribution. This study examines if morphological, anatomical, and water storage traits could explain distribution of epiphytic species in the lichen genus Usnea. Seven species from oceanic (Norway) and continental areas (Sweden) were studied. Total, internal, and external water holding capacity (WHC, mg H2O cm-2) along with relative water content (WC) were recorded by spraying the thalli with water and measuring mass after shaking and blotting. The specific thallus mass (STM, mg cm-2 - main driver of WHC) was calculated from images of wet thalli. Thickness of anatomical layers (cortex, medulla, and axis) was also measured. Pendent species had lower STM and water storage than shrubby species, most probably an adaptation to water uptake from humid air. Total, internal, and external WHC were higher in the shrubby species than in the pendent ones. The pendent species had the same internal WHC as earlier reports on Bryoria and Alectoria. External water storage decreased for all species as biomass increased. The ratio between total and internal water was twice as high as reported in foliose lichens. Variation in branch diameter was much higher in shrubby than in pendent species. The interspecific differences in water storage reflect regional differences in water sources – oceanic species had higher water storage than pendent continental species, but lower than the shrubby U. hirta. I conclude that both internal and external water storage help to explain distribution of Usnea in Norway and Sweden.

  • 341.
    Eriksson, Amanda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gauslaa, Yngvar
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ekström, Magnus
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Esseen, Per-Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Morphology drives water storage traits in the globally widespreadlichen genus Usnea2018In: Fungal ecology, ISSN 1754-5048, E-ISSN 1878-0083, Vol. 35, p. 51-61Article in journal (Refereed)
    Abstract [en]

    Links between lichen morphology, internal/external water storage and distribution patterns are poorly known. We compared mass- (WC, % H2O) and area-based (WHC, mg H2O cm−2) hydration traits in seven pendent or shrubby Usnea species from oceanic to continental climates. All species held more external than internal water. Internal WHC and WC increased with specific thallus mass (STM, mg cm−2), while external WC decreased. Shrubby species had higher STM and total WHC than pendent ones. The continental Usnea hirta (shrubby) had the highest total and external storage; the suboceanic Usnea longissima (pendent) had the lowest internal storage. Morphology drives hydration traits and explains distributions of some Usnea species, but such traits did not distinguish oceanic from widespread species. Shrubby species maximize water storage and thus prolong hydration after rainfall events and/or hydration by dew. The low internal WHC in pendent species is likely an adaptation to frequent hydration in humid air.

  • 342.
    Eriksson, Anna-Maria
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Response and recovery of ectomycorrhizal fungal sporocarp production following nitrogen fertilization in boreal forest2005Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 343. Eriksson, Britas Klemens
    et al.
    Rubach, Anja
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Batsleer, Jurgen
    Hillebrand, Helmut
    Cascading predator control interacts with productivity to determine the trophic level of biomass accumulation in a benthic food web2012In: Ecological research, ISSN 0912-3814, E-ISSN 1440-1703, Vol. 27, no 1, p. 203-210Article in journal (Refereed)
    Abstract [en]

    Large-scale exploitation of higher trophic levels by humans, together with global-scale nutrient enrichment, highlights the need to explore interactions between predator loss and resource availability. The hypothesis of exploitation ecosystems suggests that top-down and bottom-up control alternate between trophic levels, resulting in a positive relationship between primary production and the abundance of every second trophic level. Specifically, in food webs with three effective trophic levels, primary producers and predators should increase with primary production, while in food webs with two trophic levels, only herbivores should increase. We provided short-term experimental support for these model predictions in a natural benthic community with three effective trophic levels, where the number of algal recruits, but not the biomass of gastropod grazers, increased with algal production. In contrast, when the food web was reduced to two trophic levels by removing larger predators, the number of algal recruits was unchanged while gastropod grazer biomass increased with algal production. Predator removal only affected the consumer-controlled early life-stages of algae, indicating that both the number of trophic levels and the life-stage development of the producer trophic level determine the propagation of trophic cascades in benthic systems. Our results support the hypothesis that predators interact with resource availability to determine food-web structure.

  • 344. Eriksson, Lennart
    et al.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A graphical index of separation (GIOS) in multivariate modeling2010In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 24, no 11-12, p. 779-789Article in journal (Refereed)
    Abstract [en]

    We introduce a new measure for the importance of predictor variables, X, for the separation of two groups (classes) of observations. The measure is a Graphical Index of Separation (GIOS), and is, for each predictor, determined from the distribution of all possible pairs of observations with one from each group. GIOS is quantitative, intuitively simple and easy to interpret. The GIOS is straightforward to visualize in bivariate plots, and line or bar plots for larger number of variables. The approach applies both to discriminant analyses such as LDA, SIMCA, PLS-DA, OPLS-DA and to quantitative modeling such as MLR, PLS and OPLS. In the latter case, the observations are first divided into two groups based on their response values, Y. The GIOS approach is illustrated by PLS-DA/OPLS-DA and SIMCA-classification of a number of multivariate data sets with few and many variables relative to the number of observations.

  • 345.
    Eriksson, Louise
    et al.
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History, Economic and social geography.
    Nordlund, Annika
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Westin, Kerstin
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History, Economic and social geography.
    The general public´s support for forest policy in Sweden: a value belief approach2013In: Journal of Environmental Planning and Management, ISSN 0964-0568, E-ISSN 1360-0559, Vol. 56, no 6, p. 850-867Article in journal (Refereed)
    Abstract [en]

    In the present study, the legitimacy of the forest policy in Sweden was explored. Based on a value belief approach, the general public's support for forest policy was examined by means of a questionnaire (n=796). Results demonstrated that the respondents believed ecological principles, such as sustaining natural conditions for native plants and animals, were most important in forest policy, but preservation of social values and using the forest efficiently to maintain high market value were also emphasised. Although socio-demographic variables (i.e. gender and age) had some impact on support for the policy, different values and beliefs reflecting ecological, social and economic interests were more important. By considering different values and beliefs, as well as policy support explicitly, the study provides a multifaceted account of the public's viewpoint regarding forest issues.

  • 346.
    Eriksson, Ove E
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The non-lichenized ascomycetes of Sweden2009Book (Other (popular science, discussion, etc.))
  • 347.
    Eriksson, Stina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Impact of vegetation on soil and lake DOC and δ13C2009Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The climate change is expected to affect especially alpine areas negatively, replacing the alpine flora with subalpine forest. The understanding of how vegetation influences total organic carbon (TOC) in soil, streams and lakes in alpine and subalpine areas will lead to a better understanding of the effects of climate change, and will also increase the knowledge of the ecotone as a whole. In this study plant-soil relations were examined in a subalpine and an alpine catchment in the north of Sweden, by comparing dissolved organic carbon (DOC) concentrations, 13C-DOC, 13 compared with lake and stream water DOC, as well as sediment OC from the recipient lakes in the catchments.

     The results show that subalpine forests at lower altitudes, have higher DOC concentrations, higher C:N ratios, and more depleted Particulate OM in water and inlets, show that allochthonous carbon influences water properties in both catchments, as does primary production by benthic and pelagic algae, separating shallow and deep sediment Differences between the catchments are explained with the higher primary production of organic material and root exudations from trees in the subalpine forested catchment effecting the whole catchment dynamics. C-SOM and the carbon to nitrogen (C:N) ratios. The terrestrial bulk chemical properties of DOC were alsoδ13C signals in soil, and soil-solution compared to alpine areas. δ13C signals from Dissolved OM andδ13C signals.

  • 348.
    Eriksson, Torleif
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Migratory behaviour of Baltic salmon (Salmo salar L.): adaptive significance of annual cycles1988Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis evaluates the adaptive significance of annual cycles on the migratory behaviour of Baltic salmon (Salmo salar L.). The studies have included field experiments as well as laboratory studies gf maturity and migratory behaviour patterns of smolts and postsmolts mainly from the Angerman river population.

    Contrasting to the phenotypical elasticity in life-history traits, Baltic salmon was found to have a rather strict temporal organization of their annual behavioural patterns. Two year old smolted Baltic salmon showed drastic differences in migratory behaviour when compared in tanks containing either fresh or brackish water. Freshwater kept fish showed an annual cycle where downstream displacement in the upper water column was followed by a stationary behaviour, indicating a readaption to a freshwater life. Fish in brackish water behaved as a migratory fish throughout tne study. Baltic salmon also showed differences in maturation patterns in fresh and brackish water. Three summer old males detained in freshwater all matured sexually the following autumn. If transferred to sea and kept in net- pens a low proportion matured, mainly previously matured males. Furthermore there was a size- dependent relationship of sexual rematuration. Many small previously matured males did not migrate, similarly small previolusly matured males were unable to respond to shifts in the environment. With larger size the alternatives of sexual maturation and high growth rate wi more related to the environmental conditions the fish experienced.

    A hypothesis has been tested assuming that Baltic salmon migration is influenced by an annual time program. According to the hypothesis the migratory distance covered in the Baltic should be a result of a migratory activity sequence rather than a definite goal orientation. Fish detained before release generally showed a shorter distance between release point and area of recapture compared to fish released at normal time of smoltrun. The migratory distance appeared to be inversly related to the period of delay before release. A seasonal difference in migratory propensity was recorded.

    An instantaneous mortality curve for Baltic salmon during seaward migration and early sea-phase was estimated based on recapture data on sequentially related fish. The weekly mortality rate decreased from an initial mean of 271 during onset of migration, to 3.51 in mean during autumn. The high risk of mortality during the first part of migration indicated that strong selective forces act on a precise seasonal timing of migration.

  • 349.
    Eriksson, Torleif
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Mortality risks of Baltic salmon (Salmo salar L.) during downstream migration and the early sea-phase [Elektronisk resurs]: effects of body-size and season1988Manuscript (preprint) (Other academic)
    Abstract [en]

    Mortality risks in Baltic salmon during early migration was estimated through a sequential release experiment. Effects of time of release and size of fish on survival rate were studied.

    A protected transfer to the sea and an acclimatization prior to release increased the recapture rates by 1.6 to 2.0 times compared to fish released in the river. Furthermore, fish with a delayed release had a 2.8 to 5.0 times higher recapture rate than smolts released in the river.

    I found a strong positive correlation between the size of the fish and recapture rates during all three experimental years. Mortality rates peaked during the downstream migration and entry in to the sea. The weekly risk of mortality during the two first weeks was estimated to be 27.8%. Thereafter the mortality risk declined rapidly to 6.1% per week during the following 8-9 weeks. From mid September until the end of November the estimated mortality rate was only 3.5% per week.

    Baltic salmon appears to migrate at a sub-optimal size with respect to survival during migration. A gain in survival by a larger size during migration,could be obtained by a prolonged freshwater residency. However this is considered to be outweighted by the option of an accelerated growth rate in the sea.

  • 350.
    Eriksson Wiklund, Ann-Kristin
    et al.
    Department of Applied Environmental Science, ITM, Stockholm University, 106 91 Stockholm, Sweden.
    Dahlgren, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Sundelin, Britta
    Department of Applied Environmental Science, ITM, Stockholm University, 106 91 Stockholm, Sweden.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Effects of warming and shifts of pelagic food web structure on benthic productivity in a coastal marine system2009In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 396, p. 13-25Article in journal (Refereed)
    Abstract [en]

    It has been predicted that climate change will lead to increased temperature and precipitation in northern latitudes, which in turn may lead to brownification of coastal sea areas. This will increase the importance of the heterotrophic microbial food web in areas like the northern Baltic Sea. Such a structural change in the pelagic food web would hamper benthic productivity, since microheterotrophs have lower settling rates than phytoplankton. We tested how variation in temperature and alteration of the pelagic food web structure affected the productivity of a key benthic species, the amphipod Monoporeia affinis, and the pelagic-benthic food web efficiency (FWE). Using water from the northern Baltic Sea, a mesocosm experiment was performed in which the temperature was altered by 5°C. The structure of the pelagic food web changed from one based on algae to one based on bacteria. Amphipod productivity was 3 times higher and FWE was 25 times higher in the algae than in the bacteria-based food web, showing that an altered pelagic food web will have severe effects on benthic productivity. Temperature variation, on the other hand, did not cause any changes in either growth of M. affinis or FWE. Our data indicate that indirect effects of climate change, leading to structural changes in the pelagic food web, will have much more severe effects on benthic productivity than the direct effect of increased temperature.

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