Knotted Pearlwort
27th July 2008, SundayA new species for me in the past week has been knotted pearlwort Sagina nodosa. This tiny pretty plant was growing in one of the more artificial habitats on the Dungeness RSPB Reserve.
Knotted pearlwort has declined significantly in south-east England since the 1950’s with the only recent records in Kent being at Dungeness and Sandwich Bay. It is also recorded in the Rye area in East Sussex.
There were hundreds of these tiny attractive plants growing on the artificial sandy margins of a gravel pit. The sand had been deposited in the pit to try to reduce the chances of saline water getting into the Dungeness aquifer from the Denge Marsh Sewer. Bare silty-sand is a waste product of the gravel industry that can be usefully dumped along the margins of gravel pits. Here it produces a habitat akin to a dune slack that supports a variety of rarities including insects such as the beetle Omophron limbatum, the rare moss Bryum warneum and Britains largest population of the Jersey cudweed Gnaphthalium luteoalbum.
The problem with these habitats is that many of the rare and interesting spceies are associated with the early successional stages of bare sand or sparsely vegetated sand. Often such sand has been used to form areas of shallow water for reeds, but its worth remembering the suite of rarities associated with more open habitats, although how you stop the vegetation choking out the rarities is not so easy!