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  • 1. Althuizen, Inge H. J.
    et al.
    Lee, Hanna
    Sarneel, Judith M
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology and Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands.
    Vandvik, Vigdis
    Long-Term climate regime modulates the impact of short-term climate variability on decomposition in alpine grassland soils2018Inngår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, nr 8, s. 1580-1592Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Decomposition of plant litter is an important process in the terrestrial carbon cycle and makes up approximately 70% of the global carbon flux from soils to the atmosphere. Climate change is expected to have significant direct and indirect effects on the litter decomposition processes at various timescales. Using the TeaBag Index, we investigated the impact on decomposition of short-term direct effects of temperature and precipitation by comparing temporal variability over years, versus long-term climate impacts that incorporate indirect effects mediated through environmental changes by comparing sites along climatic gradients. We measured the initial decomposition rate (k) and the stabilization factor (S; amount of labile litter stabilizing) across a climate grid combining three levels of summer temperature (6.5-10.5 degrees C) with four levels of annual precipitation (600-2700 mm) in three summers with varying temperature and precipitation. Several (a)biotic factors were measured to characterize environmental differences between sites. Increased temperatures enhanced k, whereas increased precipitation decreased k across years and climatic regimes. In contrast, S showed diverse responses to annual changes in temperature and precipitation between climate regimes. Stabilization of labile litter fractions increased with temperature only in boreal and sub-alpine sites, while it decreased with increasing precipitation only in sub-alpine and alpine sites. Environmental factors such as soil pH, soil C/N, litter C/N, and plant diversity that are associated with long-term climate variation modulate the response of k and S. This highlights the importance of long-term climate in shaping the environmental conditions that influences the response of decomposition processes to climate change.

  • 2. Bakker, Elisabeth S.
    et al.
    Sarneel, Judith
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Gulati, Ramesh D.
    Liu, Zhengwen
    van Donk, Ellen
    Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints2013Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 710, nr 1, s. 23-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottlenecks for restoration of submerged macrophyte vegetation with a high biodiversity and focus on the biotic factors, including the availability of propagules, herbivory, plant competition and the role of remnant populations. We found that the potential for restoration in many lakes is large when clear water conditions are met, even though the macrophyte community composition of the early 1900s, the start of human-induced large-scale eutrophication in Northwestern Europe, could not be restored. However, emerging charophytes and species rich vegetation are often lost due to competition with eutrophic species. Disturbances such as herbivory can limit dominance by eutrophic species and improve macrophyte diversity. We conclude that it is imperative to study the role of propagule availability more closely as well as the biotic interactions including herbivory and plant competition. After abiotic conditions are met, these will further determine macrophyte diversity and define what exactly can be restored and what not.

  • 3. Bakker, Elisabeth S.
    et al.
    Veen, Ciska G. F.
    Ter Heerdt, Gerard J. N.
    Huig, Naomi
    Sarneel, Judith M
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology and Biodiversity Group, Utrecht University, Utrecht, Netherlands; Plant Ecophysiology Group, Utrecht University, Utrecht, Netherlands.
    High grazing pressure of geese threatens conservation and restoration of reed belts2018Inngår i: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 9, artikkel-id 1649Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reed (Phragmites australis (Cav.) Trin. ex Steud.) beds are important habitat for marsh birds, but are declining throughout Europe. Increasing numbers of the native marsh bird, the Greylag goose (Anser anser L.), are hypothesized to cause reed bed decline and inhibit restoration of reed beds, but data are largely lacking. In this study, we experimentally tested the effect of grazing by Greylag geese on the growth and expansion of reed growing in belts along lake shorelines. After 5 years of protecting reed from-grazing with exclosures, reed stems were over 4-fold denser and taller than in the grazed plots. Grazing pressure was intense with 50-100% of the stems being grazed among years in the control plots open to grazing. After 5 years of protection we opened half of the exclosures and the geese immediately grazed almost 100% of the reed stems. Whereas this did not affect the reed stem density, the stem height was strongly reduced and similar to permanently grazed reed. The next year geese were actively chased away by management from mid-March to mid-June, which changed the maximum amount of geese from over 2300 to less than 50. As a result, reed stem density and height increased and the reed belt had recovered over the full 6 m length of the experimental plots. Lastly, we introduced reed plants in an adjacent lake where no reed was growing and geese did visit this area. After two years, the density of the planted reed was six to nine-fold higher and significantly taller in exclosures compared to control plots where geese had access to the reed plants. We conclude that there is a conservation dilemma regarding how to preserve and restore reed belts in the presence of high densities of Greylag geese as conservation of both reed belts and high goose numbers seems infeasible. We suggest that there are three possible solutions for this dilemma: (1) effects of the geese can be mediated by goose population management, (2) the robustness of the reed marshes can be increased, and (3) at the landscape level, spatial planning can be used to configure landscapes with large reed bed reserves surrounded by unmown, unfertilized meadows.

  • 4. Beltman, B.
    et al.
    Van Der Ven, P. J. M.
    Verhoeven, J. T. A.
    Sarneel, J. M.
    Phosphate Release Upon Long- and Short -Term Flooding of Fen Meadows Depends on Land Use History and Soil pH2014Inngår i: Wetlands (Wilmington, N.C.), ISSN 0277-5212, E-ISSN 1943-6246, Vol. 34, nr 5, s. 989-1001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Flooding of acidified and desiccated fen meadows is a management approach for mitigating loss of plant species as well as a short-term measure to prevent flooding in urban areas. Studies have shown that flooding events can cause extreme P release from soils. We questioned whether the occurrence of this 'internal eutrophication' from flooding depended on fertilization history and soil pH. A greenhouse experiment with soil cores from Ireland (turloughs) and from the Netherlands, exposed to flooding for 216 days (long-term) showed a substantial P release for sites with a history of fertilizer use only. Short-term flooding (20-25 days) caused little P release in all soils. There was no correlation between P release and initial soil pH (range 4.1-7.1). All flooded soils showed a significant decline in sulfate and increased iron in the pore water upon flooding. Field trials applying short term flooding to sites differing in soil pH, average soil moisture and history of fertilizer application showed there was no overall effect of flooding on phosphate, nitrate, ammonium, iron concentrations and pH of pore water. Sulfate concentrations significantlyincreased. Hence, problematic phosphate release is only induced by long term flooding of fen meadows with a history of fertilization.

  • 5. Fanin, Nicolas
    et al.
    Bezaud, Sophie
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Departement of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
    Cecchini, Sebastien
    Nicolas, Manuel
    Augusto, Laurent
    Relative Importance of Climate, Soil and Plant Functional Traits During the Early Decomposition Stage of Standardized Litter2019Inngår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Climatic factors have long been considered predominant in controlling decomposition rates at large spatial scales. However, recent research suggests that edaphic factors and plant functional traits may play a more important role than previously expected. In this study, we investigated how biotic and abiotic factors interacted with litter quality by analyzing decomposition rates for two forms of standardized litter substitutes: green tea (high-quality litter) and red tea (low-quality litter). We placed 1188 teabags at two different positions (forest floor and 8 cm deep) across 99 forest sites in France and measured 46 potential drivers at each site. We found that high-quality litter decomposition was strongly related to climatic factors, whereas low-quality litter decomposition was strongly related to edaphic factors and the identity of the dominant tree species in the stand. This indicates that the relative importance of climate, soil and plant functional traits in the litter decomposition process depends on litter quality, which was the predominant factor controlling decomposition rate in this experiment. We also found that burying litter increased decomposition rates, and that this effect was more important for green tea in drier environments. This suggests that changes in position (surface vs. buried) at the plot scale may be as important as the role of macroclimate on decomposition rates because of varying water availability along the soil profile. Acknowledging that the effect of climate on decomposition depends on litter quality and that the macroclimate is not necessarily the predominant factor at large spatial scales is the first step toward identifying the factors regulating decomposition rates from the local scale to the global scale.

  • 6.
    Herberg, Erik R.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Kiel School of Sustainability, Christian-Albrechts-Universitat zu Kiel, Kiel, Germany.
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, CH Utrecht, The Netherlands.
    Recruitment of riparian plants after restoration of geomorphic complexity in northern Sweden2017Inngår i: Applied Vegetation Science, ISSN 1402-2001, E-ISSN 1654-109X, Vol. 20, nr 3, s. 435-445Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Question: Restoration of channelized streams increases geomorphic complexity but it remains unclear how this interacts with processes that drive future vegetation changes (dispersal, germination and establishment). This study asks if increased geomorphic complexity increases recruitment conditions of sown seeds or affects post-dispersal natural seedling densities. Location: Vindel River catchment, northern Sweden. Methods: We selected seven study streams with paired reaches that differed in the degree to which geomorphic complexity was restored. Basic reaches used simple restoration methods while enhanced reaches additionally added large boulders and woody debris. We sowed seeds of six species at ten locations in each reach in 2014 and counted the number of seedlings after 8wk and the number of naturally occurring seedlings in a plot adjacent to the sowing locations in 2013 and 2014. Using factor analysis based on 34 complexity measurements, overall geomorphic complexity was quantified for eight of the 14 reaches. Results: Total numbers of sown (2014) and natural seedlings (2013 and 2014) summed per reach did not differ between restoration types when tested pair-wise. Enhanced restoration did not always significantly increase geomorphic complexity, which differed considerably between the streams. More complex reaches were steeper, had larger size sediment and more nutrient-poor soils. Total recruitment of sown species significantly decreased with increasing complexity. Numbers of natural seedlings differed considerably from 2013 to 2014, but were not related to complexity. In 2014, a potential parent plant of the same species occurred within the same plot for 71.8% of the natural seedlings that could be identified. Conclusions: The recruitment of sown seeds was affected by overall geomorphic complexity rather than by the enhanced restoration. The absence of a correlation between geomorphic complexity and natural seedlings could indicate that natural seedling dynamics are not solely determined by recruitment conditions, but also by dispersal.

  • 7. Hidding, Bert
    et al.
    Sarneel, Judith M
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bakker, Elisabeth S
    Flooding tolerance and horizontal expansion of wetland plants: facilitation by floating mats?2014Inngår i: Aquatic Botany, ISSN 0304-3770, E-ISSN 1879-1522, Vol. 113, s. 83-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water level fluctuations (WLF) can be important disturbances promoting the diversity of riparian plant communities, but are currently absent from many managed aquatic ecosystems. A lack of WLF is thought to reduce plant diversity and hamper hydrosere succession. However, a positive impact of WLF on plant diversity may crucially depend on nutrient availability and the presence of a potential ecosystem engineer, the floating plant Strati otes abides, that may provide structural support to riparian plants. We tested the interactive effects of 40 cm flooding, presence of S. abides and sediment nutrient availability (N and P) on growth and horizontal expansion of eight wetland plant species in a 10 week experiment. Seven out of eight species showed a significant elongation response to flooding. Compared to stagnant water levels, flooding in combination with high nutrient availability decreased horizontal expansion in two short species and increased it in two tall species, whereas flooding decreased horizontal expansion in two other short species under both nutrient levels. In this 10 week experiment, we observed no effect of S. abides on the measured plant parameters. This experiment shows short-term negative effects of flooding on most of the short species. On the long-term, we hypothesize that improvements in water quality and seedling recruitment due to drawdown may result in net positive effects of WLF in the riparian zone, but as the species that were rare in the field happened to be short, care should be taken to maintain rare species when allowing more WLF.

    (C) 2013 Elsevier B.V. All rights reserved.

  • 8. Keuskamp, Joost A.
    et al.
    Dingemans, Bas J. J.
    Lehtinen, Taru
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
    Hefting, Mariet M.
    Tea Bag Index: a novel approach to collect uniform decomposition data across ecosystems2013Inngår i: Methods in Ecology and Evolution, ISSN 2041-210X, E-ISSN 2041-210X, Vol. 4, nr 11, s. 1070-1075Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. Changes in the balance between soil carbon storage and release can significantly amplify or attenuate global warming. Although a lot of progress has been made in determining potential drivers of carbon release through large-scale decomposition experiments, climate predictions are still hampered by data limitation at a global scale as a result of high effort and measurement costs of comparative litter decomposition studies.

    2. We introduce an innovative, cost-effective, well-standardised method to gather data on decomposition rate and litter stabilisation using commercially available tea bags as standardised test kits. By using two tea types with contrasting decomposability, we can construct a decomposition curve using a single measurement in time. The acquired Tea Bag Index (TBI) consists of two parameters describing decomposition rate (k) and litter stabilisation factor (S).

    3. The method was tested for its sensitivity and robustness in contrasting ecosystems and biomes, confirming that the TBI is sensitive enough to discriminate between these systems. Within an ecosystem, TBI is responsive to differences in abiotic circumstances such as soil temperature and moisture content. The collected k and S values are in accordance with expectations based on decomposition process literature. They are therefore interpretable within the current knowledge framework.

    4. Tea Bag Index is a unique, multifunctional method requiring few resources and minimal prior knowledge. The standardisation and simplicity of the method make it possible to collect comparable, globally distributed data through crowdsourcing. TBI can further provide an excellent decomposition reference and has the potential to increase reliability of soil carbon flux estimates based on extrapolations of decomposition data.

  • 9.
    Nilsson, Christer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Polvi, Lina E
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Gardeström, Johanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Maher Hasselquist, Eliza
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lind, Lovisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sarneel, Judith M
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Riparian and in-stream restoration of boreal streams and rivers: success or failure?2015Inngår i: Ecohydrology, ISSN 1936-0584, E-ISSN 1936-0592, Vol. 8, nr 5, s. 753-764Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Nilsson, Christer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Riis, Tenna
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Biology Department of Utrecht University, in the Netherlands.
    Svavarsdóttir, Kristín
    Ecological Restoration as a Means of Managing Inland Flood Hazards2018Inngår i: BioScience, ISSN 0006-3568, E-ISSN 1525-3244, Vol. 68, nr 2, s. 89-99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many streams and rivers experience major floods. Historically, human societies have responded to such floods by moving away from them or by abating them, the latter with large negative impacts on stream and river ecology. Societies are currently implementing a strategy of "living with floods,"which may involve ecological restoration. It further involves flood mapping, forecasting, and warning systems. We evaluate 14 different stream-and river-restoration measures, which differ in their capacity to modify water retention and runoff. We discuss these restoration measures in the light of predicted changes in climate and flooding and discuss future restoration needs. We focus on the Nordic countries, where substantial changes in the water cycle are foreseen. We conclude that sustainable solutions require researchers to monitor the effect of flood management and study the relative importance of individual restoration measures, as well as the side effects of flood attenuation.

  • 11.
    Nilsson, Christer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
    Palm, Daniel
    Gardeström, Johanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pilotto, Francesca
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Polvi, Lina E.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lind, Lovisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Holmqvist, Daniel
    Lundqvist, Hans
    How do biota respond to additional physical restoration of restored streams?2017Inngår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 20, nr 1, s. 144-162Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 12.
    Polvi, Lina E.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Utrecht, Netherlands.
    Ecosystem engineers in rivers: An introduction to how and where organisms create positive biogeomorphic feedbacks2018Inngår i: WIREs Water, ISSN 0935-879X, E-ISSN 2049-1948, Vol. 5, nr 2, artikkel-id e1271Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ecosystem engineers substantially alter physical flow characteristics and shape a river's form and function. Because the recurrence interval of geomorphic processes and disturbances in rivers commonly match the temporal scale of plants' life cycles or alterations by animals, the resulting feedbacks are an important component of rivers. In this review, we focus on biota that directly or indirectly induce a physical change in rivers and cause positive feedbacks on the functioning of that organism. We provide an overview of how various ecosystem engineers affect rivers at different temporal and spatial scales and plot them on a conceptual gradient of river types. Various plants engineer the river environment through stabilizing sediment and reducing flow velocities, including macrophytes, woody plants, and algal mats and biofilms. Among animals that engineer, beaver that build dams cause substantial changes to river dynamics. In addition, benthic macroinvertebrates and mussels can stabilize sediment and reduce velocities, and aquatic and riparian grazers modulate the effect of plants. Humans are also considered river ecosystem engineers. Most of the ecosystem engineers reported in literature occur in rivers with low to intermediate relative stability, intermediate channel widths, and small to intermediate grain sizes. Ecosystem engineers that create positive biogeomorphic feedbacks are important to take into account when managing river systems, as many common invasive species are successful due to their engineering capabilities. River restoration can use ecosystem engineers to spur holistic recovery. Future research points towards examining ecosystem engineers on longer spatial and temporal scales and understanding the co-evolution of organisms and landforms through engineering. 

  • 13.
    Sarneel, J. M. Judith
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
    Veen, G. F. Ciska
    Legacy effects of altered flooding regimes on decomposition in a boreal floodplain2017Inngår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 421, nr 1-2, s. 57-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Since long-term experiments are scarce, we have poor understanding of how changed flooding regimes affect processes such as litter decomposition. We simulated short- and long-term changed flooding regimes by transplanting turfs between low (frequently flooded) and high (in-frequently flooded) elevations on the river bank in 2000 (old turfs) and 2014 (young turfs). We tested how incubation elevation, turf origin and turf age affected decomposition of standard litter (tea) and four types of local litter. For tea, we found that the initial decomposition rate (k) and stabilization (S) of labile material during the second decomposition phase were highest at high incubation elevation. We found intermediate values for k and S in young transplanted turfs, but turf origin was not important in old turfs. Local litter mass loss was generally highest at high incubation elevations, and effects of turf origin and turf age were litter-specific. We conclude that incubation elevation, i.e., the current flooding regime, was the most important factor driving decomposition. Soil origin (flooding history) affected decomposition of tea only in young turfs. Therefore, we expect that changes in flooding regimes predominantly affect decomposition directly, while indirect legacy effects are weaker and litter- or site-specific.

  • 14.
    Sarneel, Judith
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    The dispersal capacity of vegetative propagules of riparian fen species2013Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 710, nr 1, s. 219-225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Flowing water can disperse a high number of seeds and vegetative propagules over long distances and is therefore a very important dispersal vector in wetland habitats. Although the dispersal of seeds is relatively well studied, the dispersal of vegetative propagules has received less attention. However, in riparian and aquatic systems where many species have clonal growth forms, it can be very important. The relative importance of vegetative propagules in the dispersal of fen species was assessed first by determining their relative abundance in the field and second, by determining the buoyancy of plant fragments of ten fen species experimentally. On average, vegetative propagules made up 3.2-58.9% of the total propagule number (mainly Elodea nutallii). Buoyancy of the tested species ranged from 25 days to over 6 months. Surprisingly, the propagules of Stratiotes aloides and Hydrocharis morsus-ranae increased buoyancy when spring started (after ca. 100 days). The results demonstrate that vegetative propagules of riparian and aquatic fen species have a high capacity to disperse over long distances via water and are therefore likely to play an important role in the colonisation of new habitats. Especially because in nine out of the ten species tested, over 50% of the propagules were still viable after 6 months of floating.

  • 15.
    Sarneel, Judith
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Huig, N.
    Veen, G. F.
    Rip, W.
    Bakker, E. S.
    Herbivores Enforce Sharp Boundaries Between Terrestrial and Aquatic Ecosystems2014Inngår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 17, nr 8, s. 1426-1438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transitions between ecosystems (ecotones) are often biodiversity hotspots, but we know little about the forces that shape them. Today, often sharp boundaries with low diversity are found between terrestrial and aquatic ecosystems. This has been attributed to environmental factors that hamper succession. However, ecosystem properties are often controlled by both bottom-up and top-down forces, but their relative importance in shaping riparian boundaries is not known. We hypothesize that (1) herbivores may enforce sharp transitions between terrestrial and aquatic ecosystems by inhibiting emergent vegetation expansion and reducing the width of the transition zone and (2) the vegetation expansion, diversity, and species turnover are related to abiotic factors in the absence of herbivores, but not in their presence. We tested these hypotheses in 50 paired grazed and ungrazed plots spread over ten wetlands, during two years. Excluding grazers increased vegetation expansion, cover, biomass, and species richness. In ungrazed plots, vegetation cover was negatively related to water depth, whereas plant species richness was negatively related to the vegetation N:P ratio. The presence of (mainly aquatic) herbivores overruled the effect of water depth on vegetation cover increase but did not interact with vegetation N:P ratio. Increased local extinction in the presence of herbivores explained the negative effect of herbivores on species richness, as local colonization rates were unaffected by grazing. We conclude that (aquatic) herbivores can strongly inhibit expansion of the riparian vegetation and reduce vegetation diversity over a range of environmental conditions. Consequently, herbivores enforce sharp boundaries between terrestrial and aquatic ecosystems.

  • 16.
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology and Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Utrecht, The Netherlands.
    Effects of experimental snowmelt and rain on dispersal of six plant species2016Inngår i: Ecohydrology, ISSN 1936-0584, E-ISSN 1936-0592, Vol. 9, nr 8, s. 1464-1470Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water flows affect dispersal of propagules of many plant species, and rivers and streams are therefore very important dispersal vectors. However, small water flows such as trough rain and snowmelt are much more common, but their effects on dispersal are barely studied. The importance of this form of dispersal deserves attention, especially when considering that climate change is predicted to change the amounts of rain and snow worldwide. Dispersal through melting snow and rain was addressed experimentally, using artificial soils mounted on slopes with different angles and subjected to a melting snow pack or an equivalent amount of dripping water. Seeds on the soil moved on average 3.02 cm (+/- 1.81 SE) in rain treatments and 0.23 cm (+/- 0.3 SE) in snowmelt treatments. Tracking plastic granules in field conditions further showed that snowmelt exhibited minimal dispersal capacity. Dispersal distances by rain were enhanced by increasing slope angles and with decreasing seed volume. Given that many species in cold environments have small seeds, dispersal by rain could provide an important (secondary) dispersal mechanism in these habitats.

  • 17.
    Sarneel, Judith M.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology and Environmental Sciences, Utrecht University, Utrecht, The Netherlands.
    Bejarano, Maria D.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Natural Resources Department, Technical University of Madrid, Madrid, Spain.
    van Oosterhout, Martin
    Nilsson, Christer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Local flooding history affects plant recruitment in riparian zones2019Inngår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 30, nr 2, s. 224-234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims: Many rivers across the globe are severely impacted by changed flooding regimes, resulting in drastic shifts in vegetation, but the processes driving the exchange of flood‐sensitive and flood‐tolerant species are understood less. We studied the role of long‐term and recent flooding histories for riparian plant recruitment in response to various changes in flooding regime.

    Location: Vindel River catchment (Northern Sweden).

    Methods

    We experimentally changed long‐term flooding regimes by transplanting turfs between high and low elevations in 2000 and in 2014 (= 8 per treatment). We sowed seeds of five riparian species in both transplanted turfs and non‐transplanted controls and counted seedling numbers over two growing seasons. Further, we inventoried natural seedling frequencies in 190 plots in 19 reaches in 2013 and 2014, and related natural seedling numbers to plot flooding history in the period 2012–2014.

    Results: We observed effects of long‐term flooding history in the second year of the transplantation study (2015), but not in the first year. In 2015, turfs transplanted to locations with less flooding resulted in higher plant recruitment while transplantation to sites with more frequent flooding reduced recruitment compared to the controls. Since these differences were only found in recently transplanted turfs and not in older turfs, the legacy effect of long‐term flooding history can be transient. In the field seedling survey, similar differences were found between flooding‐history categories in 2013, but not in 2014, when the moisture conditions of the most recent year determined flooding. Further, lowest seedling numbers were observed when the previous flooding occurred in winter, and higher seedling numbers when floods occurred in spring or not at all.

    Conclusions: Both long‐term and recent flooding histories can affect plant recruitment, and their influence should be taken into account when designing restoration projects.

  • 18. Sarneel, Judith M.
    et al.
    Beltman, Boudewijn
    Buijze, Anneke
    Groen, Roderick
    Soons, Merel B.
    The role of wind in the dispersal of floating seeds in slow-flowing or stagnant water bodies2014Inngår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 25, nr 1, s. 262-274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    QuestionWhat is the role of wind in the dispersal of waterborne seeds in slow-flowing and stagnant water bodies at different temporal and spatial scales? (i) Is there a direct effect of wind on seed dispersal speed and distance? (ii) Are prevailing wind conditions reflected in the seed deposition patterns during a year? (iii) What are the long-term (multiple year) effects of prevailing wind conditions on the pattern and composition of shoreline seed banks? LocationThe Westbroekse Zodden (5210N; 507E) and De Weerribben (52 degrees 46N; 5 degrees 55E) fen reserves in The Netherlands. MethodsReal-time seed movement tracking experiments were conducted at different wind speeds. Additionally, we performed a seed trap experiment using artificial grass mats and carried out seed bank analyses using a seedling emergence test. ResultsWind speed and direction strongly determined the dispersal process and the resulting deposition patterns of floating seeds in shallow lakes or ponds. Wind speed directly influenced dispersal speed and distance. Increasing wind speed increased dispersal speed but decreased dispersal distance. Over multiple seasons, more seeds were deposited at downwind shorelines than at upwind shorelines, showing that wind-driven hydrochory resulted in directional transport according to the prevailing wind direction. The species composition of deposited seeds was also affected, with proportionally more water-dispersed seeds being deposited at down-wind shorelines. These effects of wind speed and directionality will have consequences for the colonization of riparian zones in lentic systems and, therefore, also influence management and restoration. In the long term, local seed banks in riparian zones reflected the prevailing wind conditions poorly, showing that additional processes, such as differential germination and predation, also play important roles at longer time scales. ConclusionsWind plays an important role in the dispersal of waterborne seeds in lentic systems and (prevailing) wind speed and direction are reflected in seed dispersal trajectories and deposition patterns.

  • 19.
    Sarneel, Judith M.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity, Institute of Environmental Biology, Utrecht University, Utrecht, Netherlands; Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Utrecht, Netherlands.
    Hefting, Mariet M.
    Kowalchuk, George A.
    Nilsson, Christer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Van der Velden, Merit
    Visser, Eric J. W.
    Voesenek, Laurentius A. C. J.
    Jansson, Roland
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Alternative transient states and slow plant community responses after changed flooding regimes2019Inngår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 25, nr 4, s. 1358-1367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Climate change will have large consequences for flooding frequencies in freshwater systems. In interaction with anthropogenic activities (flow regulation, channel restoration and catchment land-use) this will both increase flooding and drought across the world. Like in many other ecosystems facing changed environmental conditions, it remains difficult to predict the rate and trajectory of vegetation responses to changed conditions. Given that critical ecosystem services (e.g. bank stabilization, carbon subsidies to aquatic communities or water purification) depend on riparian vegetation composition, it is important to understand how and how fast riparian vegetation responds to changing flooding regimes. We studied vegetation changes over 19 growing seasons in turfs that were transplanted in a full-factorial design between three riparian elevations with different flooding frequencies. We found that (a) some transplanted communities may have developed into an alternative stable state and were still different from the target community, and (b) pathways of vegetation change were highly directional but alternative trajectories did occur, (c) changes were rather linear but faster when flooding frequencies increased than when they decreased, and (d) we observed fastest changes in turfs when proxies for mortality and colonization were highest. These results provide rare examples of alternative transient trajectories and stable states under field conditions, which is an important step towards understanding their drivers and their frequency in a changing world.

  • 20.
    Sarneel, Judith M.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Janssen, Roel H.
    Rip, Winnie J.
    Bender, Irene M. A.
    Bakker, Elisabeth S.
    Windows of opportunity for germination of riparian species after restoring water level fluctuations: a field experiment with controlled seed banks2014Inngår i: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 51, nr 4, s. 1006-1014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. Restoration activities aiming at increasing vegetation diversity often try to stimulate both dispersal and germination. In wetlands, dispersal and germination are coupled as water and water level fluctuations (WLF) simultaneously influence seed transport and germination conditions (soil moisture). Water regime shifts have been shown to affect vegetation composition. However, the interactions between WLF, dispersal and subsequent germination as drivers of such changes are still poorly understood, especially within the complexity of a field situation.

    2. We tested the effect of soil moisture on ten riparian species in the greenhouse and sowed these species on 135 field locations in nine wetlands with recently restored WLF. We used quantile regressions to test the effects of WLF on the window of opportunity for germination from sown seeds and other seeds naturally dispersed to our plots, as well as on community diversity.

    3. Soil moisture significantly affected germination both in the greenhouse and in the field. In the complexity of a field situation, a flooding depth just below the soil level, an intermediate flooding duration and a high flooding frequency provided the best opportunities for maximal germination. This was because these conditions enhanced germination from the seed bank as well as increasing germination from dispersed seeds. Seedling diversity showed identical patterns.

    4. Other known (i.e., light conditions) and unknown factors played a role as we found low and variable germination, even under optimal conditions. We found evidence that WLF can affect vegetation zonation as flooded seedling communities contained more species with high moisture affinity.

    5. Synthesis and applications. Water level fluctuations provide clear windows of opportunity for germination both from the seed bank and from dispersed seeds. Water regime changes are therefore likely to strongly affect recruitment opportunities and subsequent community assembly in riparian ecosystems, for instance through climate change or management. Water level fluctuations can be used as management tool to stimulate plant recruitment and seedling diversity in riparian wetlands.

  • 21.
    Sarneel, Judith M.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
    Kardol, Paul
    Nilsson, Christer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    The importance of priority effects for riparian plant community dynamics2016Inngår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 27, nr 4, s. 658-667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Questions The order of plant species arrival can affect recruitment and subsequent plant community development via priority effects, but is often overlooked. Priority effects occur when early-colonizing plant species affect the establishment of later-arriving species, and are hypothesized to depend on species identity and habitat conditions. In riparian ecosystems on the banks of rivers, a strong moisture gradient induces a zonation of plant species with different degrees of adaptation to soil moisture. Further, riparian zones receive seeds during floods and later in the season via wind dispersal. As such, we questioned if recruitment in riparian zones is primarily affected by (1) environmental conditions (i.e. soil moisture), (2) arrival order, and (3) species identity, or an interaction between these factors.

    Location Riparian zones of tributaries in the Vindel River catchment, northern Sweden.

    Method We designed a controlled greenhouse experiment and a large-scale field experiment where we sowed five plant species representing different dispersal events and habitat moisture preferences. We sowed seeds in three arrival order treatments (all species simultaneously, species group A phased 3wk before group B, and vice versa) and under different soil moisture treatments in the greenhouse (dry, dry-after-wet and wet) and under a range of moisture conditions in the field.

    Results We found strong priority effects as early-arriving species grew bigger and often produced higher seedling densities compared to later-arriving species, both in the greenhouse and after two growing seasons in the field. Priority effects in the greenhouse were strongest in the dry and dry-after-wet treatments and weaker under wet conditions. Consistent but weaker patterns were observed in the field after the first growing season. The relative abundance of species in plant communities assembled without phased arrival interacted with soil moisture and species identity. Priority effects were strongest for species with a low relative abundance (i.e. less competitive species).

    Conclusions Our findings that priority effects influenced recruitment and interacted with soil moisture suggest that priority effects should be considered when addressing riparian vegetation changes after shifts in flooding regimes. This is especially important because floods will not only affect habitat conditions, but also the phasing of seed arrival.

  • 22. van Leeuwen, Casper H. A.
    et al.
    Sarneel, Judith M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    van Paassen, Jose
    Rip, Winnie J.
    Bakker, Elisabeth S.
    Hydrology, shore morphology and species traits affect seed dispersal, germination and community assembly in shoreline plant communities2014Inngår i: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 102, nr 4, s. 998-1007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. Seed dispersal and germination are two primary processes influencing plant community assembly. On freshwater shores, water levels regulate both processes. However, it is still unclear how water levels, shore morphology and species traits interactively affect seed dispersal and germination, and how these interactions determine plant community assembly. We hypothesize that a drawdown water regime enhances seed establishment compared to a year-round stable water level, that this increases species richness and diversity, and that this is modulated by species traits and shore morphology. 2. Germination of 20 wetland plant species with different dispersal capacities (floating capacity expressed as seed floatation half-time) and soil moisture preferences for germination (Ellenberg F) was tested on artificial shores in 24 outdoor ponds in two complementary experiments over 8 weeks. The 'dispersal experiment' tested the effect of water regime on recruitment of hydrochorously dispersing seeds. The 'seed bank experiment' tested the effect of water regime on germination from a sown seed bank, on steep and gradual shores. 3. In the dispersal experiment, the drawdown regime increased recruitment and species richness. Longer floating species colonized a larger shoreline section. Soil moisture preference for germination did not determine colonization patterns. 4. In the seed bank experiment, the drawdown regime increased the number of seedlings on gradual sloping shores, but not on steep shores. The number of germinating seedlings corresponded to the area subjected to the drawdown regime in both shore types. Species richness was not affected by water regime or shore morphology, and species traits did not determine shoreline colonization. Most seeds germinated in moist soil conditions for all species. 5. Synthesis. A spring drawdown instead of stable water regime stimulates establishment of hydrochorously dispersing seeds in temperate wetlands, leading to higher species richness and diversity. Germination from the seed bank is more affected by water regime and shore surface than by the tested species traits. Species traits, water levels and shore morphology together determine wetland plant community assembly, with dispersal as the main driver of seedling community diversity. Water-level regulations and shore morphology can be used to influence plant communities in wetland restoration.

  • 23. Veen, GF (Ciska)
    et al.
    Sarneel, Judith M
    Department of Aquatic Ecology, Netherlands Institute of Ecology, Wageningen, The Netherlands.
    Ravensbergen, Lone
    Huig, Naomi
    van Paassen, Jose
    Rip, Winnie
    Bakker, Elisabeth S
    Aquatic grazers reduce the establishment and growth of riparian plants along an environmental gradient2013Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 58, nr 9, s. 1794-1803Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. The establishment of riparian plants is determined by abiotic conditions and grazing, although it is usually presumed that the former are most important. We tested the impact of aquatic grazers on the survival and growth of establishing riparian plants and whether the impact of grazing interacts with abiotic conditions.

    2. We conducted an experiment across 10 Dutch wetlands, covering a large range of water depth and nutrient availability. We introduced 1-year-old plants of an emergent (common reed, Phragmites australis) and a floating (water soldier, Stratiotes aloides) species in individual enclosures (n=5 per site) that excluded predominantly waterbirds, which were the most abundant grazers, and on adjacent unprotected plots. Survival and growth were measured during one growing season.

    3. Grazing reduced growth (as biomass) of Phragmites and Stratiotes by a mean of 25 and 60%, respectively. Grazing decreased survival of Stratiotes, but not of Phragmites. Shallow water, water-level fluctuations, eutrophic conditions and enough light favoured both growth and survival of Phragmites. Growth of Stratiotes was unaffected by these factors, but they reduced its survival. For both species, grazing effects on biomass were consistent across environmental conditions, but for Phragmites, grazing effects on survival were influenced by abiotic conditions.

    4. We conclude that aquatic grazers significantly reduce the establishment and growth of macrophytes in the riparian zone over a wide range of environmental conditions.

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