Judith M. Sarneel
Umeå University
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Featured researches published by Judith M. Sarneel.
Hydrobiologia | 2013
Elisabeth S. Bakker; Judith M. Sarneel; Ramesh D. Gulati; Zhengwen Liu; Ellen Van Donk
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.
Environmental Pollution | 2009
Jeroen Geurts; Judith M. Sarneel; Bart J.C. Willers; J.G.M. Roelofs; Jos T. A. Verhoeven; Leon P. M. Lamers
Both eutrophication and SO4 pollution can lead to higher availability of nutrients and potentially toxic compounds in wetlands. To unravel the interaction between the level of eutrophication and toxicity at species and community level, effects of SO4 were tested in nutrient-poor and nutrient-rich fen mesocosms. Biomass production of aquatic and semi-aquatic macrophytes and colonization of the water layer increased after fertilization, leading to dominance of highly competitive species. SO4 addition increased alkalinity and sulphide concentrations, leading to decomposition and additional eutrophication. SO4 pollution and concomitant sulphide production considerably reduced biomass production and colonization, but macrophytes were less vulnerable in fertilized conditions. The experiment shows that competition between species, vegetation succession and terrestrialization are not only influenced by nutrient availability, but also by toxicity, which strongly interacts with the level of eutrophication. This implies that previously neutralized toxicity effects in eutrophied fens may appear after nutrient reduction measures have been taken.
Journal of Ecology | 2014
Casper H. A. van Leeuwen; Judith M. Sarneel; Jos e van Paassen; Winnie J. Rip; Elisabeth S. Bakker
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 ...
Journal of Applied Ecology | 2014
Judith M. Sarneel; Roel H. Janssen; Winnie J. Rip; Irene M. A. Bender; Elisabeth S. Bakker
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 leve ...
Ecosystems | 2010
Judith M. Sarneel; Jeroen Geurts; Boudewijn Beltman; Leon P. M. Lamers; M. M. Nijzink; Merel B. Soons; Jos T. A. Verhoeven
Riparian ecosystems can harbor great diversity and provide important ecological functions such as improving water quality. The impact of eutrophication on riparian ecosystems, however, is unclear. We conducted a mesocosm experiment to study the effects of nutrient loading on riparian ecosystems. We specifically asked whether the source of nutrients in the riparian zone affects the complex interactions that occur between surface water and adjacent wetlands. We also studied litter decomposition in the wetland component of the mesocosms, because litter accumulation in fens is assumed to control succession toward floating mats. Each mesocosm consisted of an upland component, referred to as the bank, and a water compartment. The bank and water compartments were planted with typical riparian zone and open water fen species prior to the addition of nitrogen (N) and phosphorus (P) in different combinations to either the bank or the surface water. Nutrient addition (mainly P) resulted in increased plant production and higher expansion rates of plants on the bank and in the water. There were also clear interactions in plant responses between the bank and water. Only eutrophic species increased shoot densities after fertilization. Nutrient addition further resulted in higher litter production, especially on the banks, and stimulated decomposition. Both the plant responses and the litter experiment indicated that eutrophication would accelerate succession to floating mats. Such floating fen mats are not likely to have the typical species-rich combination of desirable species; however, as our results suggest that they would be dominated by a few eutrophic species.
Ecosystems | 2014
Judith M. Sarneel; Naomi Huig; G. F. (Ciska) Veen; Winnie J. Rip; Elisabeth S. Bakker
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.
BioScience | 2018
Christer Nilsson; Tenna Riis; Judith M. Sarneel; Kristín Svavarsdóttir
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 s ...
Plant and Soil | 2017
Judith M. Sarneel; G. F. Ciska Veen
Background and aimsSince long-term experiments are scarce, we have poor understanding of how changed flooding regimes affect processes such as litter decomposition.MethodsWe 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.ResultsFor 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.ConclusionWe 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.
Applied Vegetation Science | 2017
Erik R. Herberg; Judith M. Sarneel
Question: Restoration of channelized streams increases geomorphic complexity but it remains unclear how this interacts with processes that drive future vegetation changes (dispersal, germination an ...
Ecohydrology | 2015
Christer Nilsson; Lina E. Polvi; Johanna Gardeström; Eliza Maher Hasselquist; Lovisa Lind; Judith M. Sarneel