The restoration of species-rich heathland communities in the Netherlands

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Germination and emergence of Rumex in river flood-plains II : The role of perianth, temperature, light and hypoxia

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Restoration ecology of aquatic and terrestrial vegetation on non-calcareous sandy soils in The Netherlands

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Biodiversity, vegetation gradients and key biogeochemical processes in the heathland landscape

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In search for key biogeochemical factors for the conservation of plant species of acidic nutrient-poor habitats: comparing growth sites of common and endangered species

Summary During the last century, many plant species typical of heathland and nutrient-poor acidic grasslands have become rare whereas others have remained common. Habitat restoration often fails to enhance the rare species, which may in part be caused by the failure to restore the biogeochemical conditions suited to these species. Many soil variables have been shown to affect plant fitness but it is unknown what their relative importance is and whether any biogeochemical variable acts as a key factor constraining the persistence of rare heathland species. We compiled a data set consisting of 300 vegetation samples and the associated soil chemical properties from a range of studies carried out across the Netherlands. We asked whether growth sites of rare and common species typical of heathland and acidic grasslands differed in their biogeochemical properties, and whether growth sites of rare species displayed less variation in soil biogeochemical variables (e.g. had narrower ecological amplitude). Regardless of rarity, the species' growth sites were most accurately described by a curvilinear relationship between pH and Al/Ca ratios. Other soil characteristics did not vary systematically with changing acidity of the soil or the patterns were less pronounced. Acidification will therefore most rapidly and predictably result in an increase in Al/Ca ratio whereas this is not necessarily the case for the other soil variables affecting plant fitness. The soil ammonium (NH4) concentration and ammonium/nitrate (NH4/NO3) ratio were 3·5 and 3 times higher, respectively, in growth sites of common species compared with those of rare species. No other measured variable differed significantly between rare and common plant species. On average rare species had a significantly narrower ecological amplitude than common species for soil biogeochemical parameters. Synthesis and applications. A greater sensitivity to high NH4 concentrations in combination with a narrower ecological tolerance zone for a range of soil biogeochemical factors may explain the demise of rare species adapted to nutrient-poor acidic habitats in recent decades. Conservation management should aim to restore low NH4 concentrations and NH4/NO3 ratios. Experimental studies indicate that the most effective way to do this is through removal of the topsoil in combination with liming

Wegwijs in de natuur : achtergronden, illustraties en toepassingen van het informatiesysteem SynBioSys

De afgelopen twee jaar is door HBO en MBO onderwijs, in samenwerking met Alterra en werkveld, gewerkt aan het zodanig invullen van SynBioSys dat het bruikbaar is zowel binnen het werkveld als het onderwijs. Als laatste product van het project is tot stand gekomen: Wegwijs in de Natuur: achtergronden, illustratie en toepassingen van het Informatiesysteem SynBioSys

Ecosystem responses to differing ratios of reduced and oxidised nitrogen inputs

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