Dangers facing calcareous grasslands and juniper heathland
The various categories of risk are as follows:
- Declining condition due to inadequate or inappropriate management
- Land area lost to scrub and other encroachment
- Land area lost to forestation
- Change in vegetation due to eutrophication and intensivisation
- Loss of typical vegetation structures due to over-ageing (juniper heathland)
The detailed consequences are as follows:
Matting and encroachment
Calcareous grasslands are subject to matting if not regularly used. Matting is the first stage in the natural succession of vegetation. When grasslands fall into disuse, this gives plants which thrive below the moss and leaf litter layer the chance to send out runners, form tussocks and bind nitrogen. As a result, low-stem species which need the light or are not so aggressively competitive, like gentians and orchids, tend to be suppressed.
Shallow-soil locations are invaded by longer-stemmed or runner-forming species of the warmer margins (Trifolio-Geranietea), like zigzag clover (Trifolium medium) and willowleaf yellowhead (Inula salicina). The deeper soils of the Keuper are increasingly dominated by aggressive grasses like the heath false-brome (Brachypodium pinnatum) und meadow brome (Bromus erectus).
The project area covers all dry open-land habitats and sites with a largely open parkland appearance with individual bushes.
The suppression of the characteristic species of this habitat type results in an impoverished range of plant species.
Not only the specialised flora suffers, though. A range of specialised animal species suffer likewise. These include insects like the Jersey Tiger moth (Callimorpha quadripunctaria), various reptiles, and birds like the Red-backed Shrike (Lanius collurio).
There is a knock-on effect too. Calcareous grassland is important for the fauna of adjacent areas, so its loss affects these adjacent areas likewise.
The project features various measures to counteract this matting effect. In the final analysis, though, only regulated grazing will have a sustainable effect.
With the calcareous grassland falling into disuse, with no grazing or browsing, it gradually shifts from vegetation matting to dry sloe/blackthorn encroachment, and finally to natural forestation. The greatest danger comes from aggressive encroachment by runner-forming species like blackthorn, dogwood or wild privet, which can develop dense stands in a very short time. Woody plants whose propagation requires air-borne seeding (e.g. ash or maple) or the help of birds (e.g. hawthorn, wild rose or oak) take much longer to develop. They can only germinate if they find a patch within the vegetation or sward. Such places are at a premium when poor grassland is no longer grazed. So only few of these plants develop into free-standing elements of an open parkland.
As scrub takes over, the specialist flora and fauna is suppressed by the increasing shade and the change in the micro-climate. The shadier edges of an open parkland habitat can accommodate orchids which are normally to be found in sunny woodland (Listera ovata, Platanthera bifolia, Platanthera chlorantha, Orchis mascula). However, orchids which need the full force of the sun (such as Ophrys and some of the short-stemmed Orchis varieties) soon disappear.
To restore the sites, degraded grassland will include scrub removal. Sustained improvement will require regular grazing. Areas which are still reasonably free will require only some scrub removal, the aim being to create a mosaic of different micro-habitats.
Forestation with inappropriate species
In parts of the project area, some sites have, at various times since the Second World War, been planted with unsuitable species (e.g. spruce, various pines, and robinia). The ground is thereby in the shade, and this completely alters the local climate and the nature of the soil. Runner-forming species which are typical of fallow land (e.g. Brachypodium pinnatum, Inula salicina) grow with the planted species for a long time and determine which ground vegetation thrives. Shade-tolerant orchids of open woodland and scrubland can survive here, while the less aggressive orchids of calcareous grasslands (Pulsatilla vulgaris, Gentiana species) become ever rarer.
As leaf litter accumulates, the sites undergo profound change, with the more demanding, longer-stemmed edge-habitat species expanding at the expense of the more delicate low-nutrient indicator species. The effects include the long-term destruction of the fungal bases for orchids and of the diaspores stored in the ground. Diaspore germination remains viable for only a limited period.
The effects are particularly dramatic under robinia stands. Robinia fix nitrogen very efficiently, leading to site eutrophication.
The changes have a corresponding effect on the feeding and breeding habitats of animals dependent on open-land sites.
The danger arising from forestation affects almost all areas. Though the newly forested areas themselves may be relatively small, adjacent areas can be affected by seeding or (in the case of robinia) clonal growth.
Remedial work on potential sites should include land purchase and the removal of inappropriate growth. Ground vegetation activation will be by applying dressings of meadow flower seed (C4) incorporating calcareous grassland species.
Intensification and eutrophication
Generally speaking, it is the flat and deep-soil fields that have been put to intensive agricultural use. The project area has more intensive grassland than arable soils: this is because the heavy soils overlying the keuper marl in particular are more difficult to work under an arable regime. Grassland tends to be broken up and seeded, with high inputs of fertilizer and liquid manure. Low-input, low-nutrient meadows (6510) and low-nutrient pasture tend to be found on the peripheries, where the topography makes it difficult to use heavy machinery. This is where we find a small-scale mosaic of low-nutrient meadows and pastures, orchards with grassland, and calcareous grassland.
Low-input (non-intensive) grassland is of particular importance for calcareous grassland conservation, as some of the conservation plant species are common to both habitats.
Intensive farming inevitably means the loss of the more delicate species and the spread of the ubiquitous nitrophilic species typical of intensive grassland. The range of plants declines markedly, with flowering plants being suppressed by rank grasses.
The destruction of the microclimate and of the vegetation structure has a knock-on effect on the animal population.
Core zones need buffer zones to provide additional protection against eutrophication and pesticide input. Land purchase (B1) should therefore be supplemented by extensivisation, under biodiversity agreements (C6).
Fly tipping of refuse or inert waste has now all but ceased, though illegal practices still occur at sites that are accessible but out of sight.
Scrub removal operations are bound, though, to uncover old tips or disused pasture infrastructure. Although this will not normally be any threat to the target habitats, dealing with tipped material can add to the cost of remedial work.
Part of the project will include dealing with small amounts of tipped, non-contaminating material. More major remedial work will be a matter for the land owners. Any suspicious areas or places with sizeable amounts of tipped material will be excluded from land purchase deals. The work of restoring potential calcareous grassland will include the removal and proper disposal of tipped material (C7).
Inadequate juniper regeneration
Juniper heathland is typically associated with sheep grazing, as junipers need regular browsing for regeneration. Propagation by seeding requires bare soil (and hence grazing presence) and reasonable soil moisture during the germination phase. The general supposition is that germination is improved by the seed husks undergoing fermentation as they are chewed, i.e. that the natural ‘germination inhibition’ is reduced by grazing. Inadequate (or non-existent) grazing might be one reason for the poor level of regeneration through young growth. In existing areas with juniper heathland, regeneration has declined markedly over recent years, with the result that juniper stands are ageing badly.
The plan is to counteract this by a resumption of grazing (C6) and by planting young native junipers (C9).