Managing the sea buckthorn at Pembrey Country Park

by Sarah Wigley, Swansea University

Funding from Cwm Environmental, Countryside Council for Wales and Carmarthenshire County Council enabled a significant area of the invasive sea buckthorn to be cleared from the sand dunes at Pembrey Country Park to help restore the original dune grassland.

Sarah Wigley, an MSc student from Swansea University spent the summer surveying the dunes and reports here on the work she undertook…

Satellite images were used to provide a baseline map for the site, while a GPS device was used to verify the size and extent of sea buckthorn stands, as well as defining the cleared zones. Areas that have never been invaded by sea buckthorn can be distinguished in satellite images by their difference in colour and texture compared with the shrub. The map shows how dominant the sea buckthorn has become in the dunes, particularly as ~24.4 ha of the plant had already been cleared.

The initial stages after sea buckthorn removal showed a rather bare and open landscape due to the clearance by the mechanical machinery and flails. However, this newly available space was very quickly colonized by a variety of plant species. Within a year an average of 6.4 species were present (per m²), rising to 7.9 species after 2 years.

The majority of these emerging plants can be described as wasteland species or ‘ruderals’. The clearance also caused the organic matter and nitrate content of the soil to decrease, which is positive for encouraging colonization of native dune species.

Over time the number of typical grassland species in the clearance zones increased slightly. Species such as the dune pansy and kidney vetch were present in the cleared plots. However, the domi-nance of ruderals did not appear to lessen during the 2-year recovery period. Wasteland species have declined at other sites within a few years after clearance, therefore it is possible that this will soon happen at Pembrey.

The short-term presence of ruderals is not necessarily a negative impact as these species provide an abundance of seeds, which encourage birds to the area. While the organic matter and nitrate content of the soil have become more like levels found in native grassland areas over time, the pH appears to have significantly declined (become more acid).

This could be caused by the leaching of minerals from prolonged, heavy rainfall on exposed ground and would become problematic if it were to persist.

In the next few years it is hopeful that grassland species will continue to expand on the cleared land and the communities will become more like the native dune grassland habitat. Soil conditions will need to be monitored as we do not want any further deterioration in pH. The regrowth of sea buckthorn will need to be monitored and controlled where necessary.

Information from the Carmarthenshire Biodiversity Partnership’s November/December 2012 eNewsletter.