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  • 1. Bell, David
    et al.
    Hjältén, Joakim
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jørgensen, Dolly
    Johansson, Therese
    Forest restoration to attract a putative umbrella species, the white-backed woodpecker, benefited saproxylic beetles2015In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 12, article id 278Article in journal (Refereed)
    Abstract [en]

    Umbrella species are often spatially demanding and have limited ability to adapt to environmental changes induced by human land-use. This makes them vulnerable to human encroachment. In Sweden, broadleaved trees are disadvantaged by forestry, and commercially managed forests are often deprived of dead wood. This has led to a situation where previously widespread top predators in saproxylic food webs, such as the white-backed woodpecker (Dendrocopos leucotos), have become species of conservation concern. The white-backed woodpecker is generally considered an umbrella species, and it has been linked to forests with large volumes of dead wood from broadleaved trees. In recent years, forest stands have been restored for the white-backed woodpecker, but post-treatment evaluations have rarely included other species that also occur in broad-leaved forests (co-occurring species). Many co-occurring species are saproxylic beetles. In this study, we collected saproxylic beetles and environmental data in restored and commercially managed forests to evaluate if habitat restoration for the white-backed woodpecker also benefited other species with similar habitat associations. We found that volumes of coarse woody debris were higher in restored than in commercially managed forests, and that a majority of man-made snags and downed logs were created from birch trees (Betula spp.). Most spruce trees (Picea abies) were extracted during forest restoration, and this opened up the forest canopy, and created stands dominated by broadleaved trees. Many saproxylic beetles were more common in restored forests, and there were significant differences in species composition between treatments. These differences were largely explained by species traits. Effects of sun-exposure were particularly important, but many beneficiary species were also linked to dead wood from broadleaved trees. Red-listed saproxylic beetles showed a similar pattern with more species and individuals in restored sites. The white-backed woodpecker is still critically endangered in Sweden, but important prey species are already responding to forest restoration at the stand level. We recognize that landscape-level improvements will be required to bring the white-backed woodpecker back, but also that the umbrella species concept can provide a useful framework for successful forest restoration as many co-occurring saproxylic beetle species seemingly benefitted from restoration for the white-backed woodpecker.

  • 2.
    Bergström, Ann-Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Daniel
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vrede, Tobias
    N-limited consumer growth and low nutrient regeneration N:P ratios in lakes with low N deposition2015In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 1, article id 9Article in journal (Refereed)
    Abstract [en]

    Nutrient limitation of primary producers and their consumers can have a large influence on ecosystem productivity. The nature and strength of nutrient limitation is driven both by external factors (e.g., nutrient loading) and internal processes (e.g., consumer-driven nutrient regeneration). Here we present results from a field study in 10 low productive headwater lakes in northern subarctic Sweden, where nitrogen (N) deposition is low and phytoplankton is primarily N-limited. We assessed the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of seston and zooplankton and estimated the N:P ratio of consumer-driven nutrient regeneration. Based on stoichiometric models, the estimated elemental imbalances between seston and zooplankton suggest that zooplankton were mainly N-limited and regenerated nutrients with low N:P ratios (median 11.9, atomic ratio). The predicted N:P regeneration ratios were consistent with results from phytoplankton nutrient limitation bioassays in mid-summer, i.e., the N:P regeneration was predicted to be low when phytoplankton were N-limited, and high when phytoplankton were P-limited. During other seasons, when water discharge was high, nutrient loading from the surrounding catchments apparently had the strongest effect on phytoplankton nutrient limitation. We propose that lakes with higher N:P ratios than the open ocean is an effect of N deposition, that N-limitation of consumers and phytoplankton is further enhanced by low nutrient regeneration N:P ratios, and that in the absence of N deposition, lake and ocean N:P stoichiometry are similar.

  • 3. Cameron, Erin K.
    et al.
    Sundqvist, Maja K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. The Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen,Universitetsparken 15, 2100 Copenhagen Ø, Denmark.
    Keith, Sally A.
    CaraDonna, Paul J.
    Mousing, Erik A.
    Nilsson, Karin A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Metcalfe, Daniel B.
    Classen, Aimee T.
    Uneven global distribution of food web studies under climate change2019In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 10, no 3, article id e02645Article in journal (Refereed)
    Abstract [en]

    Trophic interactions within food webs affect species distributions, coexistence, and provision of ecosystem services but can be strongly impacted by climatic changes. Understanding these impacts is therefore essential for managing ecosystems and sustaining human well-being. Here, we conducted a global synthesis of terrestrial, marine, and freshwater studies to identify key gaps in our knowledge of climate change impacts on food webs and determine whether the areas currently studied are those most likely to be impacted by climate change. We found research suffers from a strong geographic bias, with only 3.5% of studies occurring in the tropics. Importantly, the distribution of sites sampled under projected climate changes was biased-areas with decreases or large increases in precipitation and areas with low magnitudes of temperature change were under-represented. Our results suggest that understanding of climate change impacts on food webs could be broadened by considering more than two trophic levels, responses in addition to species abundance and biomass, impacts of a wider suite of climatic variables, and tropical ecosystems. Most importantly, to enable better forecasts of biodiversity responses to dimate change, we identify critically under-represented geographic regions and climatic conditions which should be prioritized in future research.

  • 4. Classen, Aimee T.
    et al.
    Sundqvist, Maja K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Henning, Jeremiah A.
    Newman, Gregory S.
    Moore, Jessica A. M.
    Cregger, Melissa A.
    Moorhead, Leigh C.
    Patterson, Courtney M.
    Direct and indirect effects of climate change on soil microbial and soil microbial-plant interactions: What lies ahead?2015In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 8, article id 130Article in journal (Refereed)
    Abstract [en]

    Global change is altering species distributions and thus interactions among organisms. Organisms live in concert with thousands of other species, some beneficial, some pathogenic, some which have little to no effect in complex communities. Since natural communities are composed of organisms with very different life history traits and dispersal ability it is unlikely they will all respond to climatic change in a similar way. Disjuncts in plant-pollinator and plant-herbivore interactions under global change have been relatively well described, but plant-soil microorganism and soil microbe-microbe relationships have received less attention. Since soil microorganisms regulate nutrient transformations, provide plants with nutrients, allow co-existence among neighbors, and control plant populations, changes in soil microorganism-plant interactions could have significant ramifications for plant community composition and ecosystem function. In this paper we explore how climatic change affects soil microbes and soil microbe-plant interactions directly and indirectly, discuss what we see as emerging and exciting questions and areas for future research, and discuss what ramifications changes in these interactions may have on the composition and function of ecosystems.

  • 5.
    Grieve, Adrian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lau, Danny C. P.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Do autochthonous resources enhance trophic transfer of allochthonous organic matter to aquatic consumers, or vice versa?2018In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 9, no 6, article id e02307Article in journal (Refereed)
    Abstract [en]

    Autochthonous and allochthonous resources are known to differ in nutritional quality and trophic support for aquatic food webs, but it is less clear how these high- and low-quality resources interact to affect trophic transfer and consumer production. We conducted 30-d feeding trials to investigate the resource assimilation, somatic growth, and fatty-acid (FA) composition of the widespread benthic generalist isopod Asellus aquatints, in response to different ratios of low-quality allochthonous (leaf litter) to high-quality autochthonous diets (algae). Wet mass growth of Asellus was lowest when fed 100% leaf litter or algae (0.53 +/- 0.46 and 0.55 +/- 0.57 mg center dot g(-1)center dot d(-1), respectively; mean +/- SE) and highest (4.95 +/- 0.51 mg center dot g(-1)center dot d(-1)) with a diet of 90:10 leaf litter:algae ratio. Asellus tended to grow slower with increasing dietary algal proportions (10-100%), yet stable isotopes and Bayesian mixing models revealed consistently high algal assimilation (>= 94%) by Asellus. Therefore, among the mixed-diet treatments, Asellus biomass production using algal resources was optimized when terrestrial organic matter (OM) dominated over algae. Eicosapentaenoic acid (EPA):total FA, EPA:omega-3 FA, and arachidonic acid:total FA declined, but docosahexaenoic acid (DHA):omega-3 FA increased, with increasing growth of Asellus. Tissue EPA concentrations of Asellus were similar among treatments, so reductions in EPA:omega-3 and EPA:total FA were due to increases in DHA concentration. Overall, our results suggest synergistic effects between autochthonous and allochthonous resources on Asellus growth and that allochthonous OM particularly facilitates the trophic transfer of autochthonous resources. Asellus preferentially retains DHA at low algal availability. This may improve its neural tissue development and so its success in accessing algae. The growth and FA responses of the widespread Asellus can enhance resource and DHA transfer to visual predators that have greater DHA demands, particularly when brownification of boreal freshwaters likely intensifies upon global climate change.

  • 6. Heuschele, Jan
    et al.
    Ekvall, Mikael T.
    Bianco, Giuseppe
    Hylander, Samuel
    Hansson, Lars-Anders
    Context-dependent individual behavioral consistency in Daphnia2017In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 8, no 2, article id e01679Article in journal (Refereed)
    Abstract [en]

    The understanding of consistent individual differences in behavior, often termed "personality," for adapting and coping with threats and novel environmental conditions has advanced considerably during the last decade. However, advancements are almost exclusively associated with higher-order animals, whereas studies focusing on smaller aquatic organisms are still rare. Here, we show individual differences in the swimming behavior of Daphnia magna, a clonal freshwater invertebrate, before, during, and after being exposed to a lethal threat, ultraviolet radiation (UVR). We show consistency in swimming velocity among both mothers and daughters of D. magna in a neutral environment, whereas this pattern breaks down when exposed to UVR. Our study also, for the first time, illustrates how the ontogenetic development in swimming and refuge-seeking behavior of young individuals eventually approaches that of adults. Overall, we show that aquatic invertebrates are far from being identical robots, but instead they show considerable individual differences in behavior that can be attributed to both ontogenetic development and individual consistency. Our study also demonstrates, for the first time, that behavioral consistency and repeatability, that is, something resembling " personality," is context and state dependent in this zooplankter taxa.

  • 7.
    Horstkotte, Tim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Univ Lapland, Arctic Ctr, Pohjoisranta 4, FI-96101 Rovaniemi, Finland; Univ Turku, Dept Geog & Geol, FI-20500 Turku, Finland.
    Utsi, T. Aa.
    Larsson-Blind, A.
    Burgess, P.
    Johansen, B.
    Kayhko, J.
    Oksanen, L.
    Forbes, B. C.
    Human-animal agency in reindeer management: Sami herders' perspectives on vegetation dynamics under climate change2017In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 8, no 9, article id e01931Article in journal (Refereed)
    Abstract [en]

    Many primary livelihoods in Arctic and sub-Arctic regions experience accelerating effects of environmental change. The often close connection between indigenous peoples and their respective territories allows them to make detailed observations of how these changes transform the landscapes where they practice their daily activities. Here, we report Sami reindeer herders' observations based on their long-term inhabitance and use of contrasting pastoral landscapes in northern Fennoscandia. In particular, we focus on the capacity for various herd management regimes to prevent a potential transformation of open tundra vegetation to shrubland or woodland. Sami herders did not confirm a substantial, rapid, or large-scale transformation of treeless tundra areas into shrub-and/or woodlands. However, where they observe encroachment of open tundra landscapes, a range of factors was deemed responsible. These included abiotic conditions, anthropogenic influences, and the direct and indirect effects of reindeer. The advance of the mountain birch tree line was in some cases associated with reduced or discontinued grazing and firewood cutting, depending on the seasonal significance of these particular areas. Where the tree line has risen in elevation and/or latitude, herding practices have by necessity adapted to these changes. Exploiting the capacity of reindeer impacts on vegetation as a conservation tool offers time-tested adaptive strategies of ecosystem management to counteract a potential encroachment of the tundra by woody plants. However, novel solutions in environmental governance involve difficult trade-offs for ecologically sustainable, economically viable, and socially desirable management strategies.

  • 8.
    Jonsson, Micael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Snall, Tord
    Asplund, Johan
    Clemmensen, Karina E.
    Dahlberg, Anders
    Kumordzi, Bright B.
    Lindahl, Bjorn D.
    Oksanen, Jari
    Wardle, David A.
    Divergent responses of beta-diversity among organism groups to a strong environmental gradient2016In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 7, no 10, article id e01535Article in journal (Refereed)
    Abstract [en]

    A limited understanding of how variation in the species composition among communities (i.e., beta-diversity) changes along natural environmental gradients, and the mechanisms responsible, inhibits our ability to understand large-scale biodiversity change resulting from either natural or anthropogenic drivers. Therefore, our aim was to test key drivers of beta-diversity patterns along a strong, natural environmental gradient for seven widely different organisms groups, that is, root-associated fungi, litter fungi, soil nematodes, vascular plants, epiphytic lichens, beetles, and spiders. Using previously published community-level data from boreal-forested islands, we calculated alpha-diversity and beta-diversity for each of the seven organism groups. Out of several available environmental variables, we identified four variables, that is, ecosystem age, total C storage, net primary productivity (NPP), and N-to-P ratio, as potential predictors of variation in beta-diversity. We found that ecosystem age was the variable with the highest overall importance. We then used two different methods to quantify the relative importance of stochastic and deterministic processes underlying patterns in beta-diversity along the ecosystem age gradient, and our detailed knowledge based on prior data collection in the study system to mechanistically explain among-group differences in these patterns. We found divergent responses in beta-diversity along the age gradient for the seven different organism groups, due to among-group differences in the relative importance of deterministic vs. stochastic community assembly, and attributed these results to reliance on resources from different energy channels that are not always related to NPP. Our results highlight the necessity to consider the importance of taxon-specific resources, and not only NPP, to obtain an understanding of beta-diversity patterns among organism groups and ecosystems, as well as large-scale patterns in biodiversity. They therefore also suggest that management and protection of beta-biodiversity in the landscape requires explicit consideration of a wide range of habitats.

  • 9.
    Lind, Lovisa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, Troy, New York 12180 USA.
    Schuler, Matthew S.
    Hintz, William D.
    Stoler, Aaron B.
    Jones, Devin K.
    Mattes, Brian M.
    Relyea, Rick A.
    Salty fertile lakes: how salinization and eutrophication alter the structure of freshwater communities2018In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 9, no 9, article id e02383Article in journal (Refereed)
    Abstract [en]

    The quality of freshwater ecosystems is decreasing worldwide because of anthropogenic activities. For example, nutrient over-enrichment associated with agricultural, urban, and industrial development has led to an acceleration of primary production, or eutrophication. Additionally, in northern areas, deicing salts that are an evolutionary novel stressor to freshwater ecosystems have caused chloride levels of many freshwaters to exceed thresholds established for environmental protection. Even if excess nutrients and road deicing salts often contaminate freshwaters at the same time, the combined effects of eutrophication and salinization on freshwater communities are unknown. Thus by using outdoor mesocosms, we investigated the potentially interactive effects of nutrient additions and road salt (NaCl) on experimental lake communities containing phytoplankton, periphyton, filamentous algae, zooplankton, two snail species (Physa acuta and Viviparus georgianus), and macrophytes (Nitella spp.). We exposed communities to a factorial combination of environmentally relevant concentrations of road salt (15, 250, and 1000 mg Cl-/L), nutrient additions (oligotrophic, eutrophic), and sunlight (low, medium, and high) for 80 d. We manipulated light intensity to parse out the direct effects of road salts or nutrients from the indirect effects via algal blooms that reduce light levels. We observed numerous direct and indirect effects of salt, nutrients, and light as well as interactive effects. Added nutrients caused increases in most producers and consumers. Increased salt (1000 mg Cl-/L) initially caused a decline in cladoceran and copepod abundance, leading to an increase in phytoplankton. Increased salt also reduced the biomass and chl a content of Nitella and reduced the abundance of filamentous algae. Added salt had no effect on the abundance of pond snails, but it caused a decline in banded mystery snails, which led to an increase in periphyton. Low light negatively affected all taxa (except Nitella) and light levels exhibited multiple interactions with road salt, but the combined effects of nutrients and salt were always additive. Collectively, our results indicate that eutrophication and salinization both have major effects on aquatic ecosystems and their combined effects (through different mechanisms) are expected to promote large blooms of phytoplankton and periphyton while causing declines in many species of invertebrates and macrophytes.

  • 10. Magnusson, M.
    et al.
    Ecke, F.
    Khalil, H.
    Olsson, G.
    Evander, Magnus
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology.
    Niklasson, B.
    Hornfeldt, B.
    Spatial and temporal variation of hantavirus bank vole infection in managed forest landscapes2015In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 9, article id 163Article in journal (Refereed)
    Abstract [en]

    Zoonoses are major contributors to emerging infectious diseases globally. Hemorrhagic fever with renal syndrome (HFRS) is a zoonosis caused by rodent-borne hantaviruses. In Europe, Puumala hantavirus (PUUV) carried and shed by the bank vole (Myodes glareolus), is the most common cause of HFRS. We explore the relationship of PUUV infection in bank voles, as measured by PUUV antibody detection, with habitat and landscape scale properties during two successive vole cycles in boreal Sweden. Our analysis revealed that PUUV infection in the population was not uniform between cycles and across different landscapes. The mean density index of PUUV antibody positive and negative bank voles were highest in old forest, second highest in cut-over forest (approx. 0-30 years old) and lowest on mires. Most importantly, old forest was the core habitat, where PUUV antibody positive bank voles were found through the low density phase and the transition between successive vole cycles. In spring, occurrence of antibody positive voles was negatively related to the proportion of cut-over forest in the surrounding landscape, suggesting that large scale human induced land-use change altered the occurrence of PUUV infection in voles which has not been shown before. Dependence of PUUV infection on habitat and landscape structure, and the variation in infection load within and between cycles are of importance for human risk assessment.

  • 11.
    Nilsson, Karin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Refuge availability and within-species differencesin cannibalism determine population variability and dynamics2013In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 4, no 100Article in journal (Refereed)
    Abstract [en]

    Theoretical studies show that both cannibalism and intraspecific resource competition canhave major effects on population dynamics. Cannibalistic intensity, offspring size, harvesting and refugeavailability are important factors affecting the interplay between cannibalism and competition. We studiedtwo populations of the common guppy (Poecilia reticulata) that differed in their cannibalistic voracity aswell as offspring size. We manipulated the availability of refuges for juveniles and harvesting intensity oflarge adults to investigate how these factors influenced the dynamics of the two populations.Overall population dynamics was mainly affected by the origin of the founder populations and thepresence of refuges. The population with a higher cannibalistic propensity and smaller offspring exhibitedhigher population variability, and the presence of refuges reduced cannibalism and stabilised the dynamicsin both populations. Harvest of large cannibalistic females destabilised the dynamics and causedextinctions of several populations without refuges. Both populations displayed cannibal-driven cycles withrepression of recruitment when no refuges were present. Cycle periods were shorter with refuges presentand the dynamics were more cohort like with synchronised peaks in density of vulnerable juveniles andcannibals. We suggest that increased number of refuging juveniles led to intensified resource competitionin the population. The harvest yield was low in the refuge treatments as few females grew large due toresource competition, leading to a small impact of harvesting in these treatments.

  • 12.
    Nilsson, Karin A.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Refuge availability and within-species differences in cannibalism determine population variability and dynamics2013In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 4, no 8, p. 100-Article in journal (Refereed)
    Abstract [en]

    Theoretical studies show that both cannibalism and intraspecific resource competition can have major effects on population dynamics. Cannibalistic intensity, offspring size, harvesting and refuge availability are important factors affecting the interplay between cannibalism and competition. We studied two populations of the common guppy (Poecilia reticulata) that differed in their cannibalistic voracity as well as offspring size. We manipulated the availability of refuges for juveniles and harvesting intensity of large adults to investigate how these factors influenced the dynamics of the two populations. Overall population dynamics was mainly affected by the origin of the founder populations and the presence of refuges. The population with a higher cannibalistic propensity and smaller offspring exhibited higher population variability, and the presence of refuges reduced cannibalism and stabilised the dynamics in both populations. Harvest of large cannibalistic females destabilised the dynamics and caused extinctions of several populations without refuges. Both populations displayed cannibal-driven cycles with repression of recruitment when no refuges were present. Cycle periods were shorter with refuges present and the dynamics were more cohort like with synchronised peaks in density of vulnerable juveniles and cannibals. We suggest that increased number of refuging juveniles led to intensified resource competition in the population. The harvest yield was low in the refuge treatments as few females grew large due to resource competition, leading to a small impact of harvesting in these treatments.

  • 13. Rist, L.
    et al.
    Felton, A.
    Nyström, M.
    Troell, M.
    Sponseller, Ryan A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bengtsson, J.
    Österblom, H.
    Lindborg, R.
    Tidåker, P.
    Angeler, D. G.
    Milestad, R.
    Moen, Jon
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Applying resilience thinking to production ecosystems2014In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 5, no 6, p. 73-Article in journal (Refereed)
    Abstract [en]

    Production ecosystems typically have a high dependence on supporting and regulating ecosystem services and while they have thus far managed to sustain production, this has often been at the cost of externalities imposed on other systems and locations. One of the largest challenges facing humanity is to secure the production of food and fiber while avoiding long-term negative impacts on ecosystems and the range of services that they provide. Resilience has been used as a framework for understanding sustainability challenges in a range of ecosystem types, but has not been systematically applied across the range of systems specifically used for the production of food and fiber in terrestrial, freshwater, and marine environments. This paper applied a resilience lens to production ecosystems in which anthropogenic inputs play varying roles in determining system dynamics and outputs. We argue that the traditional resilience framework requires important additions when applied to production systems. We show how sustained anthropogenic inputs of external resources can lead to a "coercion'' of resilience and describe how the global interconnectedness of many production systems can camouflage signals indicating resilience loss.

  • 14. Uboni, Alessia
    et al.
    Smith, Douglas W
    Mao, Julie S
    Stahler, Daniel R
    Vucetich, John A
    Long- and short-term temporal variability in habitat selection of a top predator2015In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 6, no 4, article id 51Article in journal (Refereed)
    Abstract [en]

    Considerable theory explains the importance of understanding temporal variation in ecological processes. Nevertheless, long-term variability in habitat selection is rarely assessed or even acknowledged. We explored temporal variability in the habitat selection of a top-predator, the wolf (Canis lupus), at two time scales: interannual and seasonal variability. To do this, we developed resource utilization functions to relate wolf habitat selection to environmental variables in different years and seasons. We used radiotelemetry data collected from a wolf population in Yellowstone National Park during a 10-year period (1998-2007) and added a Year variable in the models to account for interannual variation in the studied processes. We also used a three-year data set (nested within the 10-year data set) to incorporate additional variables in the models and test for differences in short- and long-term patterns of habitat selection. Wolves exhibited seasonal variation in habitat selection with respect to distance from roads, elevation, openness, and habitat type. Habitat selection was considerably more complicated during the winter compared to summer, when wolves only selected habitat based on distance from roads. We detected clear patterns of habitat selection in the three-year data set that could not be detected in the 10-year data set, despite the longer data set had more statistical power for pattern detection. This observation is likely the result of the longer data set being comprised of several shorter-term and countervailing patterns. This explanation is also consistent with having detected significant year effects in the 10-year data set. Insomuch as habitat selection is important to conservation and management, this research is significant for demonstrating the different impressions that can be given by short-term and long-term studies. It may be common for short-term data sets to suggest patterns of habitat selection that do not prevail over longer periods of time.

  • 15. Zhao, Qiong
    et al.
    Sundqvist, Maja K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. The Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen,Universitetsparken 15, 2100 Copenhagen Ø Denmark.
    Newman, Gregory S.
    Classen, Aimée T.
    Soils beneath different arctic shrubs have contrasting responses to a natural gradient in temperature2018In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 9, no 6, article id e02290Article in journal (Refereed)
    Abstract [en]

    Shrubs commonly form islands of fertility and are expanding their distribution and dominance in the arctic due to climate change, yet how soil properties may be influenced when different species of shrubs expand under warmer climates remains less explored. Important plant traits, such as their associated root community, are linked to functionally different and dominant shrub species in the arctic and these traits likely shape biogeochemical cycling in areas of shrub expansion. Using an elevational gradient as a proxy for warming, we explored how biochemical processes beneath two important arctic shrubs varied under warmer (low elevation) and cooler (high elevation) climates. Interestingly, the influence of elevation on biogeochemistry varied between the two shrubs. At the low elevation, Betula nana L., an ectomycorrhizal shrub, had high carbon (C) degrading enzyme activities, and relatively low potential net nitrogen (N) mineralization rates. Conversely, Empetrum nigrum ssp. hermaphroditum Hagerup, an cricoid mycorrhizal dwarf-shrub, had higher enzyme activities and net N immobilization rates at the higher elevation. Further, E. nigrum ssp. hermpahroditum appeared to have a more closed C and nutrient cycle than B. nana-enzymes degrading C, N, and phosphorus were tightly correlated with each other and with total C and ammonium concentrations in the humus beneath E. nigrum ssp. hermaphroditum, but not beneath B. nana. Our results suggest differences in the warming responses of C and N cycling beneath shrub species across an arctic tundra landscape.

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