Saturday, 28 November 2015

Onllwyn Coal Tips

 A few days ago, in dismal conditions, H and I spent an hour strolling around an area of reclaimed coal tip in Onllwyn (Dulais Valley). Coal tips often support ecological mosaics of calcifuge and calcicole plants and their physical and mineral characteristics are interesting. The Onllwyn bryophyte community was remarkable for its large proportion of base-loving species; e.g. Calliergonella lindbergii, Campyliadelphus chrysophyllus, Ctenidium molluscum, Didymodon ferrugineus, Ditrichum gracile, Encalypta streptocarpa, Fissidens adianthoides, Tortella tortuosa, Trichostomum crispulum. We also noted a nice patch of Climacium dendroides.

Calliergonella lindbergii

Campyliadelphus chrysophyllus
Climacium dendroides

We usually pick up Campyliadelphus chrysophyllus as scattered individuals along tracks (often associated with Didymodon ferrugineus), but here it was present in fairly dense patches. In fact, at first I wasn't sure whether it was Campyliadelphus or small Campylium protensum. The costa in Campyliadelphus leaves is really difficult (for me) to see in the field, but later microscopic observation confirmed it.
The steep, wooded side to the coal tip had a more eclectic, luxuriant pleurocarp mixture with Eurhynchium striatum, Hylocomium splendens, Loeskyobryum brevirostre, Pseudoscleropodium purum, Rhytiydiadelphus loreus and R. triquetrus, a fairly typical community for wood and scrub on reclaimed coal tips in NPT.
Coal tips are nitrogen deficient habitat. Their ecological remediation and reclamation often involves planting nitrogen-fixing  trees, shrubs and herbaceous species in order to enrich the soil with combined nitrogen, e.g. legumes such as clovers and Sainfoin and non-legumes like Alders and Sea Buckthorn. In the last few years research into the nitrogen input dynamics of northern boreal forests (also fairly nitrogen deficient ecosystems) has revealed fascinating associations between moss species such as Pleurozium schreberi and Hylocomium splendens and free-living cyanobacteria (e.g. Nostoc) in loose 'symbiotic' nitrogen-fixing relationships. In these relationships the N-fixing cyanobacteria do not appear to integrate themselves into the tissues of these mosses in the same way as they do in the cavities found in certain liverworts (e.g. Blasia pusilla) and hornworts (e.g. Anthoceros agrestis). The reason I mention this is because some of our moss collections from Onllwyn had significant amounts of free-living colonial cyanobacteria (probably Nostoc spp.) associated with them (see photo below of colony found intermingled with Ceratodon purpureus).

Filamentous cyanobacterial colony associated with Ceratodon purpureus

The colony in the photo contains lots of heterocysts, (the larger, colourless cells in the filaments), which is where N-fixation takes place in the colony. I'm sure that most of you have observed cyanobacterial colonies like this among your collections from time to time, so I thought that it might be of interest if we occasionally note species and habitats where such associations occur in South Wales. Other nitrogen deficient habitats where you might observe this are heathland (e.g among Pleurozium and Hylocomium), bogs (among Sphagnum spp.), tarmac, and perhaps epiphytic habitats.
To put this into perpesctive, the mineral nitrogen input from the moss-cyanobacteria associations into northern boreal ecosystems is at least equal to that which comes from the atmosphere -  it is a very significant contribution.  


  1. Great selection of species Charles and some lovely images too - coal tips really are fascinating habitats. I've looked at various slimy things under the microscope and their forms always intrigue me, but I've never really thought too much about their identification or ecological significance. I'll certainly attempt to note the presence of association where it's obvious, though I'm not familiar with distinguishing filamentous algae from cyanobacteria (certainly not in the field), so will have to resort to generic slime/gunk.

  2. Field identification is impossible! But you may come across them when you examine bryos under the microscope. It's only casual observation, but even that may lead to interesting insights. As far distinguishing nitrogen-fixing Cyanobacteria from eukaryotic algae is concerned, just look for heterocysts like those in the photo. The Nostoc-type filamentous forms are fairly easy to identify as Cyanobacteria and the large colourless heterocysts are easy to see even at low power. The colonies tend to be organised into mucilagenous masses, but you may also see smaller groups of filaments in close contact with leaves. Filaments that don't have heterocysts don't fix nitrogen so they are irrelevant in this context (whatever they are).

  3. Thanks Charles, yes I've seen that type of material fairly frequently. I've just been checking samples from last Friday's visit to Cwm Ivy Tor and there were colonies mixed in with some curiously small Bryoerythrophyllum recurvirostrum (also with a few scattered shoots of Saccogyna viticulosa) found growing on a soil ledge over Limestone.

  4. Fascinating. I wasn't aware of this relationship between bryos and cyanobacteria. I'll certainly make a note of it when I come across such associations in my samples.

  5. Well done lads, onward and upwards.....

  6. I have gone through the site and read all blogs and this is a nice one:

    Environmental Remediation and Reclamation