De Levende Natuur nummer 4 van 2003 (English summary)


DLN 2003-4

The European network Natura 2000 towards completion in The Netherlands

Osieck, E.R.

This paper describes the completion of the ecological network Natura 2000 since 1998 when a special issue of this journal was published on the significance and implementation of the EU Birds and Habitats Directives in the Netherlands and Flanders (Belgium). In consequence of a judgment of the European Court of Justice on the insufficient designation of special protection areas (SPA’s) under the Birds Directive by the Netherlands (Osieck, 1998b), 49 new SPA’s were designated in March 2000 by which the total area protected under the Directive tripled to over 10,000 km2. This concerns for about 75% water; the land area covered by SPA’s amounts to 7%. Large proportions of breeding bird populations (fig. 1) and non-breeding waterbird concentrations are covered by the network. The Dutch list of sites proposed for designation under the Habitats Directive has been considered insufficient by the European Commission for quite a large number of habitats and species (cf. Osieck, 1998). Figure 2 shows per Member State in the Atlantic region the percentage of the total numbers of habitats and species which were, according to the Commission, insufficiently represented on the national lists. In May 2003 the Dutch government has submitted a completely revised list including 62 new sites to the Commission (total area 7,500 km2, overlap with SPA area 87%). The noted shortcomings on the Dutch list have been largely resolved with this revised list. For 80% of the habitat types the national coverage exceeds the 60% mark (table 1). The main imperfection in the present site list is the incomplete inclusion of some large sites. For example, of the Dutch part of the Eems-Dollard estuary only the mudflats not covered by seawater during low tide have been included and of the Veluwemeer-Wolderwijd lakes one third of the stoneworth vegetation (habitat type 3140, the primary reason for selection) has been excluded from the proposed site.

The success of restoring former species-rich heathlands can be increased by applying lime after sod cutting

Dorland, E., L.J.L. van den Berg, R. Bobbink & J.G.M. Roelofs

Wet heaths and matgrass swards have declined all over Western Europe. Their species-richness has decreased considerably due to eutrophication and acidification. Restoration measures have sometimes been successful, but not in all cases. Our research focuses on solving the bottlenecks in the restoration of heaths. Sod cutting of degraded heaths and matgrass swards results in an accumulation of ammonium in the upper soil layers. Concentrations may even reach levels that are toxic to the heathland target species. The addition of lime to the sod-cut plots proved to decrease this accumulation of ammonium. Furthermore, it increased soil pH and base cation concentrations. As a result, both germination and establishment of Arnica montana were higher in sod-cut and limed plots. A positive effect of pH increase was also found for the production of flower buds in Gentiana pneumonanthe. In conclusion, when sod cutting is combined with lime application, the soil conditions are more favourable for the return of the endangered heath-species that are sensitive to soil acidification. This will likely increase the success of restoring species-rich heathlands.

Extensive heathland of the Veluwe appears to be an open forest landscape after an ecological interpretation of the cadastral maps of 1832

Clerkx, A.P.P.M. & R.J. Bijlsma

A comparison between the first cadastral maps of 1832 and the first topographical map of 1845 of the Veluwe (central Netherlands) makes clear that a substantial part of the cadastral category heathland must be interpreted as open woodland: heathland with grazed and/or coppiced oaks as scattered trees or in clusters or clumps. In most municipalities three cadastral (tax) classes of heathland were distinguished; the highest was the least fertile and often designated as sand. Heathland classes 1 and 2 fade into the lowest classes of the category woodland (coppice). Open woodland played a much greater role in the landscape of the early nineteenth century than assumed until now. The area of woodland about 1830 is severely underestimated when calculated using the first topographical map only. Several plant species (vascular plants and mosses) characteristic of ancient woodland are restricted to the former cadastral classes heathland 1 and 2 as well as the lowest classes of coppice. There is increasing evidence that this kind of open woodland is an optimal habitat for many so called forest species, rather than closed high forests.

The use of fauna passages underneath bridges at national roads.

Veenbaas, G. & G.J. Brandjes

The Ministry of Transport, Public Works and Water Management in the Netherlands has built fauna passages among others through adapting viaducts, bridges and culverts to enable fauna safely cross roads. In 1997 a survey was carried out throughout the Netherlands on a total of 22 of these types of passageway. In 1998 and in 2000, an experimental study was conducted to find out the optimal width of a wooden passageway under a bridge and whether providing extended banks with cover material will improve their use. In this second study 22 wooden passageways and 21 so-called extended banks were studied. Information about the use was obtained from footprints and tracks, left in sandbeds and on paper, fixed on both sides of an 'ink' bed in the passageway. The target group of the footprint studies were mammals, though tracks of amphibians were collected as well. All investigated passageways were in use, however, the broader they were, the more frequently they were used and the more they were used by different species. This relationship between width and use of passageways was not seen for amphibians. The larger the openess of the whole underpass (including water flow) the higher the use of the passageway was. Extended banks seem to be the most attractive: these passageways were used by most different species. The broadening of planks only significantly increased the use of these passageways by weasels. Providing extended banks with cover material only significantly increased the use by mice and shrews.

Entering marshland with habitatmodels: management tool for marsh nesting birds

Hut, R.M.G. van der

A technique is described to quantify habitat requirements of marsh breeding birds, the carrying capacity of breeding areas and measures for management plans. Basically, a systematic inventory of vegetation structure in geographic grids is used for an analysis of habitat occupancy. Measurements taken are primarily scale, coverage and edge length of vegetation in different height classes. Besides vegetation characteristics, water level of vegetation stands and surface water characteristics are quantified. This approach turned out to be successful in predicting distribution patterns of marsh breeding birds and can give quantitative advice on management of marsh habitats. Examples are given of three fields of application: describing habitat requirements of marsh nesting bird species in terms of a habitat model, evaluation of the carrying capacity of breeding areas and quantifying management measures needed to improve carrying capacity. Examples given concern the Bittern.