De Levende Natuur nummer 5 van 2015 (English summary)
The Silver-washed Fritillary (Argynnis paphia) as indicator for the restoration of light and violet-rich hillside-woodlands
J.A. Omon, K. Veling & M.F. Wallis de Vries
The woodlands on the calcareous hillslopes of southern Limburg, in the Netherlands, are home to a diverse and characteristic flora and fauna that, however, shows a marked decline. The reasons for the decline of especially the fauna are largely unknown. Therefore, the ecological requirements of the fauna of hillside-woodlands were studied with the Silver-washed fritillary (Argynnis paphia) as model species. The research question was: Are the ecological demands of A. paphia being determined by the presence of host plants and the microclimate?
The selection of oviposition sites by this butterfly species was studied in hillside-woodlands near Nettersheim in the Eifel region in Germany. The results indicate that the females lay their eggs in crevices of the bark of coniferous trees in the vicinity of violets, the host plants. The selected oviposition sites were characterised by a higher host plant density, shorter distance from host plants and a higher light availability, when compared to randomly paired locations at a distance of 15 m.
The situation in the woodlands in Limburg, where A. paphia had been recently sighted, was compared with the situation at the oviposition sites in the Eifel. The results indicate that the stem circumference and shrub cover were higher in Limburg, while the light availability and host plant density were lower. These results confirm the hypothesis that the light availability and host plant density are too low in the woodlands of Limburg to support a stable population of A. paphia.
The results of this study are also relevant for other forest and woodland types in the Netherlands. Many forests in the Netherlands do not show a high light availability, due to a lack of active management. It is likely that A. paphia will benefit from the restoration of light and violet-rich woodlands in Limburg, but also in the rest of the Netherlands. This may also be beneficial to other rare species that are characteristic for woodlands with high structural heterogeneity.
A closer look on the habitat conditions of Bog Orchid in The Netherlands
G. van Dijk, R. Loeb, E. Brouwer, A.J.P. Smolders & N. Eimers
The Bog orchid (Hammarbya paludosa) is a small, inconspicuous orchid occurring in peatlands. The Bog orchid has experienced a strong decline during the last decades. The species occurs in wet habitats with Sphagnum mosses, in the gradient from acid to slightly alkaline conditions. Detailed measurements of the habitat of the species were however absent. In this article, results of a study on the habitat characteristics of twelve locations in The Netherlands are presented. The species was mainly found in peatland areas, but also in sandy areas with seepage of groundwater. The orchid was found in open vegetation dominated by Sphagnum species. The habitats showed slightly buffered conditions already at 10 cm below the soil surface. Due to the influence of surface water or seepage, the water table remained close to the surface even in summer. Nutrient concentrations, in particular of nitrogen, are very low. The management of the populations should be aimed at the preservation of the horizontal and vertical pH-gradient, a high groundwater table, an open vegetation structure as well as the creation of new habitats. Furthermore, a low nitrogen deposition seems indispensable. Measurements on seasonal fluctuations in pore water quality may reveal the mechanisms responsible for the pH-gradients and for the very low nutrient availability of the habitat of the Bog orchid. Major knowledge gaps exist on subjects such as mycorrhizal-plant symbiosis and interactions with habitat conditions, dispersal limitations, genetic diversity and population dynamics.
The breeding success of the Greylag - and Greater Canada geese in The Drowned Land of Saeftinghe
B. de Maat, P. Calle, J.W. Castelijns & M. Jacobusse
In 2014 we investigated the breeding success of Greylag geese (Anser anser) and Greater Canada geese (Branta Canadensis) in ‘Het Verdronken Land van Saeftinghe’ (literally translated: the Drowned land of Saeftinghe), the largest intertidal brackish marsh reserve of Europe.
Every year hundreds of Greylag geese are nesting in this area. The number of breeding Greylag geese has increased from 72 breeding pairs in 1997 to 335 pairs in 2012. The Greater Canada geese was first found breeding in 2002. In 2012 the breeding population was grown to 111 pairs.
In a set of representative research areas within Saeftinghe almost all nests of the Greylag- and Greater Canada geese were traced in 2014. Once a nest was found it was inspected weekly to see if the eggs were flooded, eaten or hatched.
A total of 117 nests of Greylag geese and 21 of Greater Canada geese were found. 6 nests of Greylag geese and 11 of Greater Canada geese were successful. Foxes turned out to be the main cause of the failure of nests. 72 nests of Greylag geese and 7 of Greater Canada geese were eaten. 5 nests of Greylag geese and 3 of Greater Canada geese were flooded.
Based on the current breeding success the breeding population Greylag- and Greater Canada geese will be further decline without replenishment from the outside.
Nature restoration aided by soil transplantations: a large-scale field experiment
F.D. van Noppen, M. Bosch, E.R.J. Wubs, L. Haanstra, W. Verbaan, G.D.B. van Houwelingen, J. Philippona , R. van Ekeris, W.H. van der Putten & T.M. Bezemer;
Soil transplantations are increasingly being applied as a means to restore former agricultural areas back into species rich habitats. There are some examples where this measure has been applied successfully. However, mechanisms are not yet clear and results differ among applications depending on the soil, vegetation and other circumstances. At the Reijerscamp, near Wolfheze in the Netherlands, soil transplantations have been carried out at a large spatial scale and evaluated. The method was compared with hay transfer and controls and either or not combined with topsoil removal. The results show that target species establish especially with the transplantation of heath sods or soil on topsoil removed plots. The soil community develops best with the transplantation of heath sods. The transplantation of species rich grassland soil was less successful, but still outperformed hay-addition. Further research should unravel the mechanisms that determine the success, so that the method can be applied effectively in different contexts in the future.
Framings of Badgers in The Netherlands 1900-2013: from vermin to cuddly animal?
H.A.C. Runhaar, M. Runhaar & J. Vink
The badger population in The Netherlands has shown a strong decline until the 1980s, mainly due to persecution and, since the 1960s, increasing traffic intensity. Due to protection measures, such as badger tunnels under roads, the emergence of badger protection groups at the national and the regional level and a more comprehensive legal protection of Badgers and their setts, the population has increased substantially. Although as a consequence the number of confrontations between Badgers and humans has increased (traffic, damage to crops, etc.), Badgers seem far less controversial than in the past, as e.g. cases of illegal killing are hardly reported anymore. This suggests that framings of Badgers have changed over time. In this paper we identify and analyse badger framings between 1900 and 2013, based on reports in almost 1,200 newspaper articles.
Rapid expansion of Badgers in the province of Overijssel; is Meles meles showing a different face?
M. Zekhuis & G.M. Gerrits
Badger numbers in Overijssel are increasing. More quickly than many would have anticipated 35 years ago, when Badgers were nearly extinct in the province. The question is how this success came about? Have Badgers undergone a change or did external circumstances alter in favour of the survival of Badgers?
Up to 1980 anthropogenic pressures - persecution and road casualties being the most important - caused a dramatic decline in the badger population and range.
These pressures abated and a resulting rapid growth of the population has proven we need to rethink the still prevailing view on badgers as highly critical, vulnerable animals.
Small-scale agricultural land is often said to be most suited for Badgers, and yet despite massive intensification of Dutch agriculture as well as urban development, Badgers are faring well. Badgers are opportunist generalists capable of adapting to wildly different ecological circumstances. Badgers in Overijssel seem to have successfully made use of the opportunities the modern landscape, in the broadest meaning of the term, has to offer them.