Jan P. Bakker's research while affiliated with University of Groningen and other places

Publications (249)

Article
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The relation between salt marsh accretion and flooding regime was quantified by statistical analysis of a unique dataset of accretion measurements using sedimentation-erosion bars, on three barrier islands in the Dutch Wadden Sea over a period of c. 15 years. On one of the islands, natural gas extraction caused deep soil subsidence, which resulted...
Article
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Strong disciplinary academic fragmentation and sectoral division in policies lead to problems regarding the management of landscapes. As a result, there is a focus on the preservation and development of either cultural or natural landscapes. We argue that framing landscapes as “natural” or “cultural” will not help sustainable management. The goal o...
Article
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A summer polder had developed a deficit in surface elevation of about 20 cm in respect to rising sea level during its almost one-hundred-year period of embankment. We addressed the questions whether the distance of the restored site to the intertidal flats and continuation of livestock grazing in the restored site could hamper surface-elevation cha...
Article
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Land abandonment has been increasing in recent decades in Europe, usually accompanied by biodiversity decline. Whether livestock grazing and mowing can safeguard biodiversity across spatial scales in the long term is unclear. Using a 48‐year experiment in a salt marsh, we compared land abandonment (without grazing and mowing) and seven management r...
Article
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Sandy coastlines are dynamic environments with potential for biodiverse habitats, such as green beaches. Green beach vegetation can develop on nutrient-poor beaches landward from embryo dunes. It is characterised by low-dynamic coastal wetland habitat such as salt marshes and dune slacks. It has been hypothesised that the establishment of green bea...
Preprint
Land abandonment is increasing in recent decades in Europe, usually accompanied by a decline in biodiversity. Whether livestock grazing and mowing can safeguard biodiversity across spatial scales in the long term is unclear. Using a 48-year experiment in a salt marsh, we compared land abandonment (without grazing and mowing) and seven management re...
Article
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The effect of rotation grazing on the biodiversity of salt marshes. In order to halt succession and to control the dominance of sea couch grass on salt marshes along the Wadden Sea coast, livestock grazing is often used for conservation management. Grazing is generally applied seasonally at constant stocking densities. Rotation grazing, where grazi...
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Evaluation of long-term management regimes is important for guiding biodiversity conservation in salt marshes. However, such long-term experiments are sparse. Using a 46-year experiment in a salt marsh, we evaluated long-term effects of eight different management regimes (treatments; control, grazing, mowing, and their combinations) on the expansio...
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Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research sp...
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For conservation management of grassland ecosystems, an important question is under which conditions large grazers induce compositional and structural variation in plant communities, which is a prerequisite for high biodiversity. Here we used two long-term projects on the mainland salt marshes of the Wadden Sea to test the hypothesis that long-term...
Article
The long‐term influence of persistent small herbivores on successional plant community configuration is rarely studied. We used an herbivore exclusion experiment along the successional gradient in a salt‐marsh system, to investigate the effects of hares and geese, and hares alone, on plant diversity at five successional stages (the earliest, two ea...
Article
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In peatland restoration we often lack an information whether re-established ecosystems are functionally similar to non-degraded ones. We re-analysed the long-term outcomes of restoration on vegetation and plant functional traits in 38 European fens restored by rewetting (18 sites) and topsoil removal (20 sites). We used traits related to nutrient a...
Article
Question: Does large-scale transfer of coastal driftline material enhance the establishment of inland brackish vegetation? Location: The Klutenplas of 11 ha, a formerly reclaimed agricultural field, north coast of the Netherlands. Methods: A large quantity of coastal driftline material of local origin was transferred to the restoration site in 2006...
Article
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Livestock grazing has been practiced in salt marshes in the Wadden Sea area since 600 B.C. Currently livestock grazing is also applied for conservation management. However, effects of such grazing management on salt marshes are likely to vary depending on the species of livestock and stocking density due to differences in the behaviour of the anima...
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The relative impact of top-down control by herbivores and bottom-up control by environmental conditions on vegetation is a subject of debate in ecology. In this study, we hypothesize that top-down control by goose foraging and bottom-up control by sediment accretion on vegetation composition within an ecosystem can co-occur but operate at different...
Article
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European coastal salt marshes are important for the conservation of numerous species of specialist plants, invertebrates, breeding and migratory birds. When these marshes are managed for nature conservation purposes, livestock grazing is often used to counter the dominance of the tall grass Elytrigia atherica, and the subsequent decline in plant sp...
Chapter
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This scene-setting chapter provides the basis for the climate change-related assessments presented in later chapters of this book. It opens with an overview of the geography, demography and major human activities of the North Sea and its boundary countries. This is followed by a series of sections describing the geological and climatic evolution of...
Chapter
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This chapter presents a review of what is known about the impacts of climate change on the biota (plankton, benthos, fish, seabirds and marine mammals) of the North Sea. Examples show how the changing North Sea environment is affecting biological processes and organisation at all scales, including the physiology, reproduction, growth, survival, beh...
Article
Restoration of riparian plant communities on bare soil requires germination of seeds and establishment of seedlings. However, species that are present in the soil seed bank do not always establish in the vegetation. Temperature, moisture conditions and soil type could play a major role in the establishment of riparian plant communities, through imp...
Chapter
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This chapter examines the impacts of climate change on the natural coastal ecosystems in the North Sea region. These comprise sandy shores and dunes and salt marshes in estuaries and along the coast. The chapter starts by describing the characteristic geomorphological features of these systems and the importance of sediment transport. Consideration...
Article
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Heterogeneity can boost biodiversity, as well as increase the resilience of an ecosystem to changing environmental conditions; therefore, it is important to understand how topographic heterogeneity in ecosystems is formed. Sandy tidal marshes have a repetitive pattern of higher elevated hummocks surrounded by lower elevated depressions, representin...
Chapter
Full-text available
This scene-setting chapter provides the basis for the climate change-related assessments presented in later chapters of this book. It opens with an overview of the geography, demography and major human activities of the North Sea and its boundary countries. This is followed by a series of sections describing the geological and climatic evolution of...
Article
QuestionsHow successful was the restoration of a salt marsh at a former summer polder on the mainland coast of the Dutch Wadden Sea 10 yr after de-embankment? What were the most important factors determining the level of restoration success?LocationNoard-Fryslân Bûtendyks, northwest Netherlands.Methods The frequencies of target plant species were r...
Article
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Livestock grazing is often recommended to preclude the development of European salt marshes into a species-poor late-successional stage that is frequently dominated by Sea couch (Elytrigia atherica). It remains unclear, however, how grazing may be optimized for conservation management in order to maintain relatively high levels of biodiversity. To...
Article
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Grazers can have a large impact on ecosystem processes and are known to change vegetation composition. However, knowledge of how the long-term presence of grazers affects soil carbon sequestration is limited. In this study, we estimated total accumulated organic carbon in soils of a back-barrier salt marsh and determined how this is affected by lon...
Article
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The widespread decline of the European brown hare (Lepus europaeus) in Europe has been attributed to both bottom-up and top-down factors, as well as climate change. Few studies have attempted to study the relative importance of these factors considered simultaneously. In this study we tested the hypotheses that hare population density is regulated...
Article
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Our study investigated how bird species richness and abundance was related to livestock grazing on salt, and brackish marshes, with an emphasis on songbirds, and shorebirds. Survey areas with a high percentage cover of tall vegetation were assumed to have experienced lower livestock grazing intensities than survey areas with a low percentage cover...
Article
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Salt marshes provide an important and unique habitat for plants and animals. To restore salt marshes, numerous coastal realignment projects have been carried out, but restored marshes often show persistent ecological differences from natural marshes. We evaluate the effects of elevation and marsh topography, which are in turn affected by drainage a...
Article
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In addition to the well-studied impacts of defecation and defoliation, large herbivores also affect plant and arthropod communities through trampling, and the associated soil compaction. Soil compaction can be expected to be particularly important on wet, fine-textured soils. Therefore, we established a full factorial experiment of defoliation (mon...
Chapter
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General introduction of rocky intertidal and salt marsh systems. The land–sea margin encompasses a variety of hard and soft-bottom habitats where organisms are exposed to a dynamic range of aquatic and atmospheric conditions dependent on a rhythm set by the tides. In this chapter, we focus on rocky intertidal and salt marsh ecosystems, which have b...
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Invasive species threaten biodiversity and incur costs exceeding billions of US$. Eradication efforts, however, are nearly always unsuccessful. Throughout much of North America, land managers have used expensive, and ultimately ineffective, techniques to combat invasive Phragmites australis in marshes. Here, we reveal that Phragmites may potentiall...
Article
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In this study we evaluate the effect of coastal realignment on the utilisation of coastal grasslands by staging geese. We assessed vegetation change and utilisation by geese using repeated mapping and regular dropping counts in both the restored marsh and adjacent reference sites. All measurements were started well before the actual re-alignment. I...
Article
The long-term regeneration of calcareous grassland after agricultural intensification is elucidated in Redhead et al. (Applied Vegetation Science, 2014). The paper generates thoughts about the impact of different pre-purchase agricultural practices. It makes the reader think about the seeming contradiction of reducing soil fertility, grazing and at...
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Funding Information This work was supported by the ANR project A-BI-ME (Activit es humaines, dynamique et gestion de la BIodiversit e en milieu MEditerran een, ANR-05-BDIV-014, 2006– 2008). Abstract In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This "worldwide leaf economics spectrum" con...
Article
The number of staging geese in northwestern Europe has increased dramatically. Growing goose numbers put strong grazing pressure on agricultural pastures. Damage to agricultural land may be mitigated by managing nature reserves in order to optimally accommodate large numbers of grazing geese. Livestock grazing has been shown to facilitate foraging...
Article
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Capsule Breeding Meadow Pipits foraged for caterpillars and large spiders in vegetation that was less heterogeneous than vegetation at random locations.Aims To gain a better understanding of the foraging ecology of breeding Meadow Pipits on grazed coastal salt marshes, we tested three hypotheses: (1) there is a positive relation between vegetation...
Article
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In this study we examined the effect of different livestock grazing treatments on breeding bird densities in a salt marsh habitat. To avoid an experiment on the large scale needed to directly measure grazing effects on bird densities, we followed a two-step approach. First, we measured vegetation micro-patterns (mosaic of lower vegetation and talle...
Article
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Semi-natural grasslands are an important habitat for endangered plant and animal species. In grasslands, low-intensity livestock grazing is frequently applied as a tool for nature conservation. We aim to investigate how different livestock species in various densities influence the state and flower production of a single plant species by selective...
Article
To what extent is the decline of characteristic dry alvar species related to the decline in the soil seed bank during scrub encroachment? We recorded the number of flower stems in the vegetation in relation to light attenuation along an encroachment series progressing from open alvar through small gaps inside dense scrub of Juniperus communis (cove...
Article
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Many studies have attempted to predict whether coastal marshes will be able to keep up with future acceleration of sea-level rise by estimating marsh accretion rates. However, there are few studies focussing on the long-term effects of herbivores on vegetation structure and subsequent effects on marsh accretion. Deposition of fine-grained, mineral...
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It is increasingly recognised that interactions between geomorphological and biotic processes control the functioning of many ecosystem types as described e.g. by the ecological theory of ecosystem engineering. Consequently, the need for specific bio-geomorphological research methods is growing recently. Much research on bio-geomorphological proces...
Article
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The purpose of this study is to experimentally determine the differences between four grazing treatments on the trampling of nests. Additionally, we examine to what extent the trampling probability of nests is higher close to a source of fresh water. We compare the trampling of artificial nests in five different grazing treatments in an experimenta...
Article
Trait-based approaches are increasingly used to obtain an insight into the functional aspects of plant communities. Since measuring traits can be time-consuming, large international databases of plant traits are being compiled to share the effort. From these databases, average trait values are often extracted per species by averaging trait values o...
Article
QuestionIn the past decades, the tall native invasive grass, Elytrigia atherica, has been increasing in frequency and dominance on salt marshes along the Wadden Sea coast. Is this rapid expansion an outcome of natural succession or is it driven by anthropogenic eutrophication resulting from atmospheric deposition? LocationSalt marshes on four back-...
Article
This chapter covers vegetation conservation, management, and restoration, with sections on agricultural exploitation and nature conservation, vegetation management in relation to a hierarchy of environmental processes, laissez-faire and the wilderness concept, target-setting, monitoring, constraints, and strategies.
Article
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Studies addressing the role of large herbivores on nitrogen cycling in grasslands have suggested that the direction of effects depends on soil fertility. Via selection for high quality plant species and input of dung and urine, large herbivores have been shown to speed up nitrogen cycling in fertile grassland soils while slowing down nitrogen cycli...
Article
Small vertebrate herbivores retard vegetation succession in young stages of barrier-island salt-marsh succession. They cannot do so at later successional stages due to increasing soil productivity by the sedimentation of nitrogen containing clay. At later, productive stages of succession, grazing by livestock can reduce the dominance of late succes...
Conference Paper
Background/Question/Methods Large grazers have a major impact on their habitat, strongly affecting above- and below ground compartments of the food web. However, the exact mechanisms via which they exert such a strong influence are poorly understood. Classically, studies have focused on the aboveground impacts these large grazers have on the ecos...
Article
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Background and aims Machine mowing, mimicking the traditional hand mowing, is often used as a successful management tool to maintain grassland biodiversity, but few studies have investigated the long-term effects of traditional versus mechanical mowing of plant communities. Machine mowing as opposed to hand mowing causes soil compaction and reducti...