Stevens C.J.,Open University Milton Keynes |
Stevens C.J.,Lancaster University |
Manning P.,Northumbria University |
Van Den Berg L.J.L.,University of York |
And 12 more authors.
Environmental Pollution | Year: 2011
While it is well established that ecosystems display strong responses to elevated nitrogen deposition, the importance of the ratio between the dominant forms of deposited nitrogen (NHx and NOy) in determining ecosystem response is poorly understood. As large changes in the ratio of oxidised and reduced nitrogen inputs are occurring, this oversight requires attention. One reason for this knowledge gap is that plants experience a different NHx:NOy ratio in soil to that seen in atmospheric deposits because atmospheric inputs are modified by soil transformations, mediated by soil pH. Consequently species of neutral and alkaline habitats are less likely to encounter high NH4 + concentrations than species from acid soils. We suggest that the response of vascular plant species to changing ratios of NHx:NOy deposits will be driven primarily by a combination of soil pH and nitrification rates. Testing this hypothesis requires a combination of experimental and survey work in a range of systems. © 2010 Elsevier Ltd. All rights reserved.
Oost A.P.,University Utrecht |
Hoekstra P.,University Utrecht |
Wiersma A.,Deltares |
Flemming B.,Senckenberg Institute |
And 10 more authors.
Ocean and Coastal Management | Year: 2012
The article focuses on the morphological development of the Wadden Sea barrier island system, with emphasis on West and East Frisian islands on several temporal and spatial scales. In addition, it integrates the insights for management purposes. Barrier island management is addressed with respect to morphology, sediment budgets, safety and natural values. We show that each of these issues is determined to some extent to various spatio-temporal scales and that the management of a barrier island has to be considered in terms of interactions on various spatial and temporal scales. Morphology of some of the barrier islands is determined by the pre-existing Pleistocene relief to a fair extent, either directly due to erosion-resistant outcrops on or near the islands, or indirectly by determining the locations where inlet systems or estuaries could develop. Where this is not the case, the larger part of the sediments are locally reworked Pleistocene or Holocene deposits eroded at the North Sea coasts of the barrier chain and deposited in the back-barrier area and on the islands as a response to sea-level rise. Hardly any sand is coming in from outside the area. In order to keep up with sea-level rise sand has thus to be nourished if coastal retreat is not allowed. During the long Holocene evolution islands and ebb-tidal deltas have been lined up during their coastward migration, forming a more or less uninterrupted barrier chain along the Frisian coasts. The present-day approach of mainly focusing on the fixation of the inhabited parts of the chain will most likely result in a de-alignment of the various parts of the chain, resulting in increasing erosion of the promontories. An inlet system is a sediment-sharing system with a tidal inlet, the ebb-tidal delta, adjacent barrier islands and the tidal basin with channels, shoals, tidal flats and salt marshes. The sand balance of a barrier island is thus directly linked to tidal inlet system development. A natural change or an intervention in the sediment-sharing system by man may thus have repercussions for the island's development. Sediment redistribution in the coastal zone may also depend on climate, as is illustrated by the rapid growth of the islands after the demise of the Little Ice Age. On the barrier islands themselves many measures were taken during the past two centuries to ensure coastal safety. The successful attempts to stabilize the coasts and dunes of the barrier islands resulted in a reduction of sand transport from and along the shoreface to the beach and onto the islands. To some extent this has been restored by applying sand nourishments. However, vertical accretion of the islands is still largely impossible due to all the older coastal protection measures still present. On the long run sedimentary dynamics are essential if the island is to accrete vertically with sea-level rise, which forms a robust and sustainable strategy to guarantee safety during the next centuries. Massive stabilization also reduced the opportunities for pioneer vegetation. Dune belts and tidal marshes have experienced a fast succession resulting in a climax vegetation and the loss of the characteristic open landscape. In order to restore nature sufficient space and time should allow natural processes to develop and to create robust ecosystems. Instead of focusing on nature conservation a paradigm shift is needed in barrier island management towards stimulating the development of natural dynamics. To our opinion the best solution is to allow the geo-biological processes to take their natural course as much as possible. Examples are given for the various parts of a prototype barrier island. Only where this is not feasible other management practices should be applied. As a rule of thumb: soft and with respect for morphodynamical integrity where possible, hard where really needed. This concept applies both to the various morpho-ecological units on the islands and to the morphological developments on larger spatio-temporal scales. © 2012 Elsevier Ltd.
Holtland W.J.,Staatsbosbeheer |
Ter Braak C.J.F.,Wageningen University |
Schouten M.G.C.,Wageningen University
Applied Vegetation Science | Year: 2010
Question: Is it possible to translate vegetation maps into reliable thematic maps of site conditions? Method: This paper presents a new method, called Iteratio, by which a coherent spatial overview of specific environmental conditions can be obtained from a comprehensive vegetation survey of a specific area. Iteratio is a database application which calculates environmental indicator values for vegetation samples (relevés) on the basis of known indicator values of a limited number of plant species. The outcome is then linked to a digitalized vegetation map (map of plant communities) which results in a spatial overview of site conditions. Iteratio requires the indicator values of a minimum of 10-20% of the species occurring. The species are given a relative weight according to their amplitudes: species with a narrow range are weighted stronger, species with a broad range are weighted weaker. Conclusion: The method presented here enables a coherent assessment of site conditions on the basis of a vegetation survey and the indicator values of a limited number of plant species. © 2009 International Association for Vegetation Science.
Van Marwijk R.B.M.,Wageningen University |
Elands B.H.M.,Wageningen University |
Kampen J.K.,Wageningen University |
Terlouw S.,Staatsbosbeheer |
And 2 more authors.
Restoration Ecology | Year: 2012
Ecological restoration efforts often encounter public resistance. Recreational visitors resist imposition of restoration efforts they fear may result in a visually unattractive area. Public support is, however, essential for restoration efforts on public lands. This study seeks insight into hiker perceptions of perceived attractiveness of nature before and after efforts to restore exotic conifer plantations to native communities containing bog and wet forest communities. Visitors (N = 247) to a Dutch National Park sorted 32 photographs depicting landscapes before and after restoration efforts. Findings show that the most attractive landscape types (bog and wet forest communities containing visible water) are results of restoration efforts and the least attractive landscape types (young deciduous and coniferous forest) are representative of traditional nature before restoration. However, the "middle category" consists of landscape types existing both before and after restoration efforts. Visitors value old coniferous and old deciduous forests as much as products of restoration that lack water. These perceptions are unrelated to either visitor characteristics or the provision of information to visitors explaining restoration goals. The continued existence of resistance to restoration strategies despite their effect on perceived landscape attractiveness implies that the experience of nature has more than only visual dimensions. We expect that more acceptable results of restoration efforts will emerge from the active engagement of the public before restoration practices take place in processes that specifically address feelings of attachment and resistance to change. © 2011 Society for Ecological Restoration International.
Verberk W.C.E.P.,Radboud University Nijmegen |
Verberk W.C.E.P.,Bargerveen Foundation |
Verberk W.C.E.P.,University of Plymouth |
van den Munckhof P.J.J.,Staatsbosbeheer |
Pollux B.J.A.,Wageningen University
Aquatic Ecology | Year: 2012
Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967-2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the groundwater. We used the 'Northern Peel region', a historically iron-rich peat landscape in The Netherlands as a case study. This allowed us to test the hypothesis that niche segregation in two closely related species of stickleback occurred along a physiological axis. Patterns in stickleback occurrence were strongly associated with spatial patterns in iron concentrations before 1979: iron-rich grid cells were avoided by three-spined stickleback (Gasterosteus aculeatus, Linnaeus 1758) and preferred by nine-spined stickleback (Pungitius pungitius, [Linnaeus, 1758]). After 1979, the separation between both sticklebacks became weaker, corresponding to a decreased influence of local groundwater on stream water quality. The way both species changed their distribution in the field provides a strong indication that they differ in their susceptibility to iron-rich conditions. These observed differences correspond with differences in their respiration physiology, tolerance of poor oxygen conditions and overall life-history strategy documented in the literature. Our results exemplify how species can partition niche along a non-structural niche axis, such as sublethal iron-rich conditions. Other fish species may similarly segregate along concentration gradients in iron, while sublethal concentrations of other metals such as copper may similarly impact fish via respiratory impairment and reduced aerobic scope. © 2012 The Author(s).
PubMed | Wageningen University, Staatsbosbeheer and Radboud University Nijmegen
Type: Journal Article | Journal: Aquatic ecology | Year: 2015
Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967-2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the groundwater. We used the Northern Peel region, a historically iron-rich peat landscape in The Netherlands as a case study. This allowed us to test the hypothesis that niche segregation in two closely related species of stickleback occurred along a physiological axis. Patterns in stickleback occurrence were strongly associated with spatial patterns in iron concentrations before 1979: iron-rich grid cells were avoided by three-spined stickleback (