Fen Management Handbook - Scottish Natural Heritage

9.8.4 Plastic membranes
On sites with very permeable soils, such as peats, it is often difficult to maintain
wetter conditions with higher water levels without affecting, or being affected by,
neighbouring land. Any functioning land drains or ditches on surrounding land are
likely to exert some influence on an intended wetland creation site.
In extreme cases, a plastic membrane can be installed to limit water movement
from the wetland to the drier surrounding land, effectively forming an independent
hydrological unit. This allows water levels within the fen to be manipulated without
affecting the surrounding area, but hydrological isolation is not necessarily a
sustainable option for many wetlands. Further information on this technique is
available from www.rspb.org.uk/sluices.
9.9 Establishing fen vegetation
The establishment of fen type vegetation on new sites can be challenging. The
following information is provided as a summary and reference for those wishing to
undertake such action, based upon available best practice knowledge. Whilst there
remain as many questions as answers, it is hoped that it will provide readers with
the confidence to try new techniques. As with any new undertaking, it is wise to
try new methods or techniques in pilot projects or test plots and monitor closely to
assess the effectiveness and lessons learnt. Only then should you undertake action
across larger areas or projects. Section 9: Monitoring to Inform Fen Management
includes guidance on monitoring techniques.
Getting the hydrological regime right is the key to successful fen
creation. Provided the site has been chosen carefully and other
fundamentals such as landform have been planned and implemented
appropriately, the rest will fall usually into place. Patience (and
monitoring) may be all that is required to successfully establish fen
vegetation. Good luck!
9.9.1 Choice of species
The choice of species for establishing fen vegetation should take
account of:
– hydrological regime
– water quality
– type of substratum
– the characteristic plant communities of the region and hydromorphological
type of wetland
– species characteristic of the area
A topographical survey may be necessary to identify the range of land
heights and planting zones. The range of water level tolerance for
various species is detailed in Newbold and Mountford (1997).
The hydrological regime and hydrochemistry of a site, including pH, alkalinity and
nutrient levels as well as depth and availability of water will determine the plants which
can be established. Certain types of fen vegetation are characteristic of peats, whilst
others can be found on a wide range of substrates. The New Atlas of the British Flora
and visits to local fen sites will provide some indication of suitable species.
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