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  • 1.
    Gardeström, Johanna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Aquatic Sciences & Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Ermold, Matti
    Goedkoop, Willem
    McKie, Brendan G.
    Disturbance history influences stressor impacts: effects of a fungicide and nutrients on microbial diversity and litter decomposition2016In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, no 12, p. 2171-2184Article in journal (Refereed)
    Abstract [en]

    Streams draining agricultural catchments are severely degraded by multiple stressors, including nutrient enrichment and pesticides. The understanding of how such stressors interact to alter ecosystem structure and function, and how responses of biota reflect their longer-term disturbance history, remains limited. We conducted a multifactorial stream microcosm experiment to investigate how elevated nutrients and a fungicide (azoxystrobin) interact to affect multiple variables associated with leaf decomposition: the biomass, sporulation rate and diversity of aquatic hyphomycete decomposers, litter decomposition rates and detritivore growth. We further manipulated decomposer species composition by using three distinct fungal assemblages drawn from streams with contrasting histories of agricultural disturbance: a forest stream, a mixed land-use stream subject to nutrient enrichment but little pesticide use, and an agricultural stream subjected to both intensive nutrient and pesticide use. We also varied the presence of the detritivorous isopod Asellus aquaticus. The fungicide azoxystrobin reduced both biomass and diversity of aquatic hyphomycetes and growth of A.aquaticus, and had negative knock-on effects on leaf decomposition and fungal sporulation. These impacts further varied with nutrient concentration. Impacts of the fungicide differed markedly among the three fungal assemblages. The agricultural assemblages were dominated by tolerant species and showed some capacity for maintaining processes under pesticide exposure, whereas diversity and functioning were strongly suppressed in the forest stream assemblage, which was dominated by stress-intolerant species. Pesticides, in interaction with other agricultural stressors, can impact microbial diversity and key ecosystem processes underlying the delivery of ecosystem services from streams. The extent of such impacts vary according to the longer-term disturbance history of the biota, and might be most acute when agricultural activity expands into previously uncultivated catchments, as is currently occurring in many regions of the world.

  • 2.
    Gardeström, Johanna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Holmqvist, Daniel
    Vindel River Fishery Advisory Board.
    Polvi, Lina E.
    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.
    Demonstration Restoration Measures in Tributaries of the Vindel River Catchment2013In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 18, no 3, p. Article Number: UNSP 8-Article in journal (Refereed)
    Abstract [en]

    Some ecological restoration projects include elements of trial and error where new measures are repeatedly tried, evaluated, and modified until satisfactory results are achieved. Thereafter, the resulting methods may be applied on larger scales. A difficult step is judging whether developed "best-practice" methods have become reasonably ecologically functional or whether further experimentation "demonstration" methods can lead to yet better results. Here, we use a stream restoration project as a case study for evaluating methods and abiotic effects and outlining stakeholder support for demonstration restoration measures, rather than only using best-practice methods. Our work was located in the Vindel River system, a free-flowing river that is part of the Natura 2000 network. The river was exploited for timber floating from 1850-1976, and rapids in the main channel and tributaries below timberline were channelized to increase timber transport capacity. Several side channels in multi-channeled rapids were blocked and the flow was concentrated to a single channel from which boulders and large wood were removed. Hence, previously heterogeneous environments were replaced by more homogeneous systems with limited habitat for riverine species. The restoration project strives to alleviate the effects of fragmentation and channelization in affected rapids by returning coarse sediment from channel margins to the main channel. However, only smaller, angular sediment is available given blasting of large boulders, and large (old-growth) wood is largely absent; therefore, original levels of large boulders and large wood in channels cannot be achieved with standard restoration practices. In 10 demonstration sites, we compensated for this by adding large boulders and large wood (i.e., entire trees) from adjacent upland areas to previously best-practice restored reaches and compared their hydraulic characteristics with 10 other best-practice sites. The demonstration sites exhibited significantly reduced and more variable current velocities, and wider channels, but with less variation than pre-restoration. The ecological response to this restoration has not yet been studied, but potential outcomes are discussed.

  • 3.
    Nilsson, Christer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Polvi, Lina E
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gardeström, Johanna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Maher Hasselquist, Eliza
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lind, Lovisa
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sarneel, Judith M
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Riparian and in-stream restoration of boreal streams and rivers: success or failure?2015In: Ecohydrology, ISSN 1936-0584, E-ISSN 1936-0592, Vol. 8, no 5, p. 753-764Article in journal (Refereed)
    Abstract [en]

    We reviewed follow-up studies from Finnish and Swedish streams that have been restored after timber floating to assess the abiotic and biotic responses to restoration. More specifically, from a review of 18 case studies (16 published and 2 unpublished), we determined whether different taxonomic groups react differently or require different periods of time to respond to the same type of restoration. Restoration entailed returning coarse sediment (cobbles and boulders) and sometimes large wood to previously channelized turbulent reaches, primarily with the objective of meeting habitat requirements of naturally reproducing salmonid fish. The restored streams showed a consistent increase in channel complexity and retention capacity, but the biotic responses were weak or absent in most species groups. Aquatic mosses growing on boulders were drastically reduced shortly after restoration, but in most studies, they recovered after a few years. Riparian plants, macroinvertebrates and fish did not show any consistent trends in response. We discuss seven alternative explanations to these inconsistent results and conclude that two decades is probably too short a time for most organisms to recover. We recommend long-term monitoring using standardized methods, a landscape-scale perspective and a wider range of organisms to improve the basis for judging to what extent restoration in boreal streams has achieved its goal of reducing the impacts from timber floating.

  • 4.
    Nilsson, Christer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sarneel, Judith M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
    Palm, Daniel
    Gardeström, Johanna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pilotto, Francesca
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Polvi, Lina E.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lind, Lovisa
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Holmqvist, Daniel
    Lundqvist, Hans
    How do biota respond to additional physical restoration of restored streams?2017In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 20, no 1, p. 144-162Article in journal (Refereed)
    Abstract [en]

    Restoration of channelized streams by returning coarse sediment from stream edges to the wetted channel has become a common practice in Sweden. Yet, restoration activities do not always result in the return of desired biota. This study evaluated a restoration project in the Vindel River in northern Sweden in which practitioners further increased channel complexity of previously restored stream reaches by placing very large boulders (> 1 m), trees (> 8 m), and salmonid spawning gravel from adjacent upland areas into the channels. One reach restored with basic methods and another with enhanced methods were selected in each of ten different tributaries to the main channel. Geomorphic and hydraulic complexity was enhanced but the chemical composition of riparian soils and the communities of riparian plants and fish did not exhibit any clear responses to the enhanced restoration measures during the first 5 years compared to reaches restored with basic restoration methods. The variation in the collected data was among streams instead of between types of restored reaches. We conclude that restoration is a disturbance in itself, that immigration potential varies across landscapes, and that biotic recovery processes in boreal river systems are slow. We suggest that enhanced restoration has to apply a catchment-scale approach accounting for connectivity and availability of source populations, and that low-intensity monitoring has to be performed over several decades to evaluate restoration outcomes.

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