Environmental and vegetational relationships of lakes, fens and turloughs in the burren
2010
Proctor, Michael C.F.
<p>The limestone country of the eastern Burren includes permanent lakes, extensive fens, and turloughs—depressions characterised by large fluctuations in water levels that become dry in summer and have distinctive vegetation. Most of the larger lakes lie on an almost level surface, draining southwards via the River Fergus into the Shannon estuary; Lough Bunny drains through the limestone north towards Galway Bay. Field evidence indicates that the lakes and fens, whether they flood in winter or not, have a relatively constant summer water level, probably because the underlying limestone is sealed by glacial drift. Their vegetation follows a normal hydrosere succession from open-water deposits (mostly calcareous marl) to reed swamp and <i>Schoenus</i> fen, culminating locally in raised bog. Present-day exposed expanses of marl are products of erosion of a former peat cover. Turloughs are characterised by unconstrained fluctuations of the water level through most or all of its vertical range. They occur where there is no barrier at the surface to drainage into the limestone, but there is sufficient hydraulic resistance to underground flow to allow water levels to rise during winter and after heavy rain. The vegetation of typical turloughs has more in common with dune slack or flood meadow communities than with true fens.</p>
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