Ashes Quarry Stanhope, 12th March 2022
Ten of us from the Durham Wildlife Trust Botany Group assembled at Ashes Quarry above Stanhope to look at the mosses and liverworts that have colonised the site. The weather was generally on our side, but a heavy shower around midday accompanied by a cold wind reminded us that winter was not yet over in the Durham Dales.
Ashes Quarry was in operation from the 1870’s to the 1940’s, the limestone rock having been dug out along a mile-long exposure on the valley side; it was mostly then transported to Consett for use in the iron industry as a flux to remove impurities as slag.
It is worth saying something about the geology of the quarry because the distribution of the mosses and liverworts is strongly associated with the different types of rock present.
The strata exploited at the quarry is part of the Great Limestone, deposited at the start of the Namurian stage of the Carboniferous geological period about 325 million years ago. It is made up of solid limestone 20 metres in thickness. Above this (forming the upper part of the Great Limestone) is a section of limestone interbedded with shale known by the quarrymen as the Tumbler Beds because of their propensity to tumble down the quarry face. In turn above these beds are the Coal Sills, made up of shale and sandstone, with thin layers of coal.
Before the limestone could be extracted, the overlying shale and sandstone had to be removed, and this overburden now forms extensive piles of waste on the quarry floor. It mostly gives rise to thin, dry soils with neutral or acidic soil reaction compared with the base-rich soils on the limestone. The various types of rock have been colonised by vegetation, including many species of moss and some liverworts.
Several mosses grow directly on the limestone, including Syntrichia montana, Ctenidium molluscum, Orthotrichum anomolum, Grimmia pulvinata, Tortula muralis, Bryum argenteum, Bryum capillare and Homalothecium sericeum. Some of the waste tips contain a proportion of limestone rubble where we also saw Homalothecium lutescens and Hypnum lacunosum.
There is a different community of mosses on the waste tips composed principally of shales and sandstones. The substrate is more acidic here, allowing Polytrichum piliferum, Polytrichum juniperinum and Dicranum scoparium to flourish, with Hypnum cupressiforme and Isothecium myosuroides favouring shady places on sandstone.
Over parts of the quarry the vegetation is more well-developed and there are several other mosses which form part of a grassland community. These include Pseudoscleropodium purum, Hylocomium splendens, Thuidium tamariscinum, Rhytidiadelphus squarrosus and Rhytidiadelphus triquetrus. Climacium dendroides and Calliergonella cuspidata grow in the wetter grassland.
Drainage on the floor of the quarry has been impeded by the waste tips, and several distinctive mosses were recorded here, including Palustriella commutata, Warnstorphia sarmentosa and Sphagnum palustre. They were growing in really wet places, a fact readily confirmed by those of us who chose to wear walking boots rather than wellingtons.
And finally we also came across a few liverworts, including Lophocolea bidentata, Pellia endiviifolia and Marchantia polymorpha.
A really good day out enjoyed by all. In addition to the species listed above we saw several other mosses, emphasising the richness of the site.
Many thanks to Richard Friend for guiding us round the quarry and showing us some of the key species that grow here.
Thanks also to Lesley Hodgson for the two close-up photographs.
Silky Wall Feather-moss
Hypnum lacunosum var. lacunosum
Marchantia polymorpha subsp. polymorpha