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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 change during the first 10 years after de-embankment of the summer polder. The surface-elevation change showed similar positive linear relationships with annual tidal flooding in both the reference salt marsh and the restored site, indicating that the surface-elevation change in the restored site was not moderated by the distance from the sea. The surface-elevation change had a clear seasonal pattern with positive values in winter and negative values during summer. The surface-elevation change was 11 mm/year in the grazed reference salt marsh and 7 mm/year in the grazed restored site, but amounted to 17 mm/year in ungrazed exclosures in the restored site, showing that grazing retarded the catching up of the elevation deficit in the restored site. The surface-elevation change within the restored site was higher close to the constructed creeks indicating the inception of levee formation. The surface-elevation change was also positively affected by the proximity of breaches in the embankment, but this effect was less clear than the effect of creeks. We conclude that the surface-elevation deficit may be compensated in the Wadden Sea summer polders by their de-embankment when sediment supply is high, whereas livestock grazing retards this process. Dug creeks increase spatial variation in the restored site.

This dataset consists of two data files and three R-scripts., This dataset consists of two data files and three R-scripts.

With the current issue, the Journal of Vegetation Science (JVS) enters its 30th year. Founded by Eddy van der Maarel, Robert Peet and Robert Neuhäusl in 1990 as an official journal of the International Association for Vegetation Science, it has always been a popular publication venue for the internationally most significant studies in plant community ecology...

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 spatial and temporal scales. We used a highly dynamic marsh system with a large population of the Greylag goose (Anser anser) to investigate the potential importance of spatial and temporal scales on these processes. At the local scale, Greylag geese grub for below-ground storage organs of the vegetation, thereby creating bare patches of a few square metres within the marsh vegetation. In our study, such activities by Greylag geese allowed them to exert top-down control by setting back vegetation succession. However, we found that the patches reverted back to the initial vegetation type within 12 years. At large spatial (i.e. several square kilometres) and temporal scales (i.e. decades), high rates of sediment accretion surpassing the rate of local sea-level rise were found to drive long-term vegetation succession and increased cover of several climax vegetation types. In summary, we conclude that the vegetation composition within this tidal marsh was primarily controlled by the bottom-up factor of sediment accretion, which operates at large spatial as well as temporal scales. Top-down control exerted by herbivores was found to be a secondary process and operated at much smaller spatial and temporal scales.

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 is then given to the role of bioengineering organisms in feedback relationships with substrate, how changes in physical conditions such as embankments affect coastal systems, and the effects of livestock. The effects of climate change—principally accelerated sea-level rise, and changes in the wind climate, temperature and precipitation—on these factors affecting coastal ecosystems are then discussed. Although the focus of this chapter is on the interaction of abiotic conditions and the vegetation, the potential impacts of climate change on the distribution of plant species and on birds breeding in salt marshes is also addressed. Climate impacts on birds, mammals and fish species are covered in other chapters.

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, behaviour and transport of individuals; the distribution, dynamics and evolution of populations; and the trophic structure and coupling of ecosystems. These complex responses can be detected because there are detailed long-term biological and environmental records for the North Sea; written records go back 500 years and archaeological records many thousands of years. The information presented here shows that the composition and productivity of the North Sea marine ecosystem is clearly affected by climate change and that this will have consequences for sustainable levels of harvesting and other ecosystem services in the future. Multi-variate ocean climate indicators that can be used to monitor and warn of changes in composition and productivity are now being developed for the North Sea

Grazers can have a large impact on ecosystem processes and are known to changevegetation composition. However, knowledge of how the long-term presence of grazers affectssoil carbon sequestration is limited. In this study, we estimated total accumulated organic carbonin soils of a back-barrier salt marsh and determined how this is affected by long-term grazing byboth small and large grazers in relation to age of the ecosystem. In young marshes, where smallgrazers predominate, hare and geese have a limited effect on total accumulated organic carbon.In older, mature marshes, where large grazers predominate, cattle substantially enhanced carboncontent in the marsh soil. We ascribe this to a shift in biomass distribution in the local vegetationtowards the roots in combination with trampling effects on the soil chemistry. These large grazersthus act as ecosystem engineers: their known effect on soil compaction (based on a previous study)enhances anoxic conditions in the marsh soil, thereby reducing the oxygen available for organiccarbon decomposition by the local microbial community. This study showed that the indirecteffects of grazing can significantly enhance soil carbon storage through changing soil abiotic conditions.This process should be taken into account when estimating the role of ecosystems inreducing carbon dioxide concentration in the atmosphere. Ultimately, we propose a testableconceptual framework that includes 3 pathways by which grazers can alter carbon storage:(1) through above-ground biomass removal, (2) through alteration of biomass distribution towardsthe roots and/or (3) by changing soil abiotic conditions that affect decomposition.

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 (monthly mowing) and soil compaction (using a rammer, annually) on a clay-rich salt marsh at the Dutch coast, aiming to disentangle the importance of these two factors. Additionally, we compared the effects on soil physical properties, plants, and arthropods to those at a nearby cattle-grazed marsh under dry and under waterlogged conditions. Soil physical conditions of the compacted plots were similar to the conditions at cattle-grazed plots, showing decreased soil aeration and increased waterlogging. Soil salinity was doubled by defoliation and quadrupled by combined defoliation and compaction. Cover of the dominant tall grass Elytrigia atherica was decreased by 80% in the defoliated plots, but cover of halophytes only increased under combined defoliation and compaction. Effects on soil micro-arthropods were most severe under waterlogging, showing a fourfold decrease in abundance and a smaller mean body size under compaction. Although the combined treatment of defoliation and trampling indeed proved most similar to the grazed marsh, large discrepancies remained for both plant and soil fauna communities, presumably because of colonization time lags. We conclude that soil compaction and defoliation differently affect plant and arthropod communities in grazed ecosystems, and that the magnitude of their effects depends on herbivore density, productivity, and soil physical properties.

Vijftig jaar bescherming van de Drentsche Aa heeft veel opgeleverd; het is het best bewaarde beekdal van de laaglanden van Noordwest Europa, beschermd natuurgebied en cultuurhistorisch erfgoed in de vorm van een gaaf heide-, beken- en esdorpenlandschap. Niet alles is goed gegaan; het is belangrijk te leren van fouten uit het verleden. De besluitvorming over het gebied heeft een heel andere vorm gekregen. Bewoners, beschermers en lokale overheden werken samen. De Rijksoverheid maakt een terugtrekkende beweging. Wat is het perspectief voor de toekomst?

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