Knud Erik Nielsen

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A new species has recently invaded coastal dune ecosystems in North West Europe. The native and expansive inland grass, Deschampsia flexuosa, progressively dominating inland heaths, has recently invaded coastal dunes in Denmark, occasionally even as a dominant species. A total of 222 coastal locations with 5,000 random sample plots have been investigated.(More)
Coastal and inland heaths constitute a dominating fraction of the relatively few semi-natural ecosystems in Denmark. At the inland heath, the soil forming factors have been active with the same vegetation type during the last 2000 years, whereas at the coastal heath, these soil forming factors have only been active over a couple of hundred years, due to the(More)
Erica tetralix is the key species on NW European wet heathlands, where it is often found to be the dominating plant species. Consequently, it is of considerable concern that the species has decreased significantly in cover from 28% to 18% over a six-year period. In order to understand the underlying causes, a structural equation modeling (SEM) approach was(More)
We report observations of disappearance of Erica tetralix in wet heathland, which is unlikely to be caused by competition, as E. tetralix is dying before its place is taken up by other species. To investigate the causes, we used both old and new data. Results showed that presence of Molinia caerulea and Calluna vulgaris were substantial in the former E.(More)
Hierarchical pin-point data from 5316 plots from 73 Danish coastal dune sites were analysed in order to describe the species diversity in dune plant communities on a regional scale. Due to the mosaic spatial pattern of the dune communities, it was decided to describe the spatial structure of each plant species in each community using a vegetation type(More)
The effect of atmospheric nitrogen deposition on the species richness of acid grasslands was investigated by combining data from a large Danish monitoring program with a large European data set, where a significant non-linear negative effect of nitrogen deposition had been demonstrated (Stevens et al., 2010). The nitrogen deposition range in Denmark is(More)
The effect of nitrogen deposition on the species richness of acid grasslands in Denmark: a comparison with a sudy performed on a European scale Journal Article How to cite: Damgaard, Christian; Jensen, Lennarth; Frohn, Lise Marie; Borchsenius, Finn; Nielsen, Knud Erik; Ejrnæs, Rasmus and Stevens, Carly J. (2011). The effect of nitrogen deposition on the(More)
The effects of reclamation and high atmospheric nitrogen deposition have for long threatened the existence of heathlands in Denmark. A high nitrogen input increases the frequency and intensity of heather beetle attacks. However, any indirect effects of these attacks on the soil water balance are seldom investigated. In autumn 1994 a 2000-year old Danish(More)
The statistical modelling of joint species abundance is currently receiving increasing attention in the ecological literature because it complements earlier descriptive accounts of the effect of disturbance on community change with quantitative measures of spatial covariation among species at different spatial scales. Using a hierarchical Bayesian approach,(More)
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