Earlier this week I carried out a bryophyte survey of the Twin Tips, two prominent colliery spoil heaps at Dare Valley Country Park, for Buglife's ongoing Coal Spoil Connections project. As part of this project I am writing a report on the value of colliery spoil for bryophytes, so it was useful to look at the bryophyte communities on the tips with a keener eye than I have when recording on
colliery spoil in the past.
Both tips are old and dominated by Heather on their steep sides and tops. Trees and scrub, especially gorse, are on the increase and now clothe some of the slopes and parts of the plateaux. It was good to see the site staff and a team of volunteers tackling some of the gorse while I was there.
The bryophytes of the heather-dominated areas were typical of what you would find on any other heather moorland: mostly Pleurozium schreberi with plenty of Hylocomium splendens, Hypnum jutlandicum and Rhytidiadelphus squarrosus. It is always nice to see Ptilidium ciliare and there were a few patches of it scattered here and there.
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| Ptilidium ciliare |
The most interesting communities on these tips were on the humid north-facing slopes, where several damp-loving species were present despite the free draining nature of the substrate. Aulacomnium palustre and Polytrichum commune were frequent, along with four species of Sphagnum: plenty of S. subnitens, some S. fimbriatum, a glorious carpet of S. capillifolium in one area and a little S. auriculatum.
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| Extensive carpet of S. capillifolium, with P. commune poking through |
There wasn't much space for smaller bryophytes among the dense cover of pleurocarps and Sphagna, though patches of Lophozia ventricosa were present with Calypogeia fissa and C. arguta. Gorse and willow stems were covered in epiphytes, including some Colura calyptrifolia on the gorse.
As I was about to leave, I noticed some coal spoil exposures on a flatter area adjacent to the tips, which is in use as a bike track. The spoil here was wetter and had been disturbed more recently, and many of the bryophytes that were present were lacking from the older, drier main tips. These included the characteristic coal spoil species Archidium alternifolium and Racomitrium ericoides, and on the sides of a ditch cut through the spoil were the most interesting finds of the day - plenty of Bryum alpinum and a little Campylopus subulatus. The latter has just a few county records, from Neath Port Talbot, so this seems to be the first for Rhondda Cynon Taf.
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| Ditch through coal spoil with Campylopus subulatus & Bryum alpinum |
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| Campylopus subulatus |
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| Bryum alpinum |
All in all around 70 species were recorded from the colliery spoils and I was left pondering the diverse communities of bryophytes that develop on this substrate and how best to conserve them.