Calcareous concretion associated with Limonium procerum (Large Sea-lavender)
Calcareous concretion associated with Limonium procerum (Large Sea-lavender) and storm damage resilience IVOR REES
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olonies of Limonium binervosum agg. (Rock Sealavender) have been known for many years on the rocky coast of Anglesey (v.c. 52) near Aberffraw (Roberts, 1986). From descriptions by Sell & Murrell (2018) they have been determined as L. procerum (C.E. Salmon) Ingr. (Large Sea-lavender). In early March 2014, shortly after the particularly stormy winter of 2013/14, several of the sites for this species were revisited. Storm surges that winter had resulted in some extremely high tides on Irish Sea coasts; the highest tide for 21 years being recorded at Liverpool on 5 December 2013, followed by another major storm surge on 3–6 January 2014 (Duigan et al, 2014). Wave swash during these events caused considerable erosion to foredunes on the south-west coast of Anglesey and damage to infrastructure. Plants in the supra-littoral zone on nearby rocky shores would also have been subject to the same abnormal wave conditions.
Observations
At Porth Lleidiog (SH 3483 6783) it was apparent that large parts of some L. procerum colonies had been torn away. Less expected, was the exposure of patches of cemented sand overlying the bedrock where L. procerum rosettes had been. Discrete pits in the concretions also indicated where the tap roots had been pulled out. The concretions also seemed to be associated specifically with Sea-lavender colonies and not with clumps of other vascular plants which had also suffered storm damage. In case the observation might be of wider ecological or geological interest, several photographs were taken (Plates 1–6). Subsequently, one of the more easily relocated concretion patches was photographed from above at intervals over six years. The images were taken on an opportunistic basis so
Rock Sea-lavender (Limonium binervosum agg.), Penmon Point, Anglesey. Photographs by the author.
not all originally had the same alignment. Rotating them using identifiable rock cracks as markers has allowed both the regrowth of the plant and the persistence of the concretion to be compared. A photograph of the same colony also happened to be available from six years before the storms. The colony is located on an outcrop of PreCambrian rock at a level only reached by wave runup when storms coincide with the biggest tides. It is towards the rear of a small south-facing beach backed by a low cliff of glacial till. Adjoining the rock most of the beach has poorly sorted medium–coarse sand in the zone from high water springs down to high water neaps with extensive intertidal rock BSBI NEWS 146 | January 2021
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