DHBlog014 · A Purbeck Bryology Group visit to Creech Heath relayed by Jim White
17th November
After several days with an abundance of rain, the forecast dry day for Thursday was welcome and reliable. Eight of us gathered at Creech Heath South, and our main problem today wasn’t rain but bright, low sun casting deep shadow on the ground, making spotting such small features as mosses quite difficult. The standing water in many places added to the challenge, but a small price to pay for a generally very fine day.
Creech Heath, especially its southern flank, has been extensively modified by former clay working, leaving many pools, clay subsoil that in places remains largely bare, and locally by the importation of chalk to harden tracks. Thus, whilst it remains essentially an acidic heathland vegetation, there is unusual habitat variety with the local addition of calcareous influences, and also bare, and currently very wet, clay surfaces. This is reflected in the bryophyte flora, with the group recording well over 50 species, in a surprising mix of habitat preferences, although we probably moved little over 500m into the site.
Typical heathland speces include Hypnum jutlandicum, Campylopus introflexus, C. pyriformis, C. brevipilus, Dicranum scoparium, Dicranella heteromalla and a little Leucobryum glaucum. Ceratodon purpureus is frequent, including along the tracks where it is joined by much Archidium alternifolium and, reflecting the calcareous influence, Barbula convoluta (Streblotrichum convolutum) and Didymodon fallax. Calliergonella cuspidata and Bryum pseudotriquetrum are also frequent in the wet clay areas, probably also naturally somewhat base-rich, and in some wet patches there is a scatter of Sphagnum denticulatum (auriculatum) and S. inundatum, with some S. subnitens and S. cuspidatum in more typical Molinia tussocks. Heavily shaded vertical sides of a small watercourse have Plagiothecium succulentum, and the liverworts Calypogeia fissa, Odontoschisma sphagni, Cephalozia bicuspidata and Lophocolea bidentata are scattered here and in tussocks; an old bonfire site has a dense carpet of Bryum capillare; and the somewhat flushed character of the site, at least locally, provides conditions for Pellia endivifolia, Dicranella varia and Pohlia melanodon. Other calcareous influence species are Eurynchium striatum, Ctenidium molluscum and Campylium chrysophyllum – all rather unexpected mosses for a heathland site. Reflecting the damp, bare surface element where competition is low are Weissia controversa and the tiny Fissidens exilis. F. taxifolius also occurs and there is a good amount of the larger F. adianthoides, another indicator of base-rich flushing.
More generalist mosses also occur of course, such as Pseudoscleropodium purum, Kindbergia praelonga, Brachythecium rutabulum and Amblystegium serpens. And finally a small stand of sallows, along with lying cut logs, provides an element of woodland epiphytes, including Isothecium myosuroides, Hypnum cupressiforme, H. resupinatum, Dicranoweisia cirrata, Frullania dilatata, Metzgeria furcata, Microlejeunea ulicina, Ulota crispa, Orthotrichum affine (Lewinskya affinis) and a little Orthotrichum (Pulvigera) lyellii.
An enjoyable day then, with good company, fine conditions and an intriguing mix of species. Not so good for clocking up lots of kilometres walked though!
1st December
A dank, still and foggy start to the day, with heavy water droplets falling from overhanging trees and limited visibility was deceptive, as from late morning there were hints of blue sky and breaking of the cloud. The six moss hunters that gathered at Creech Heath to explore the western side of the reserve were further rewarded with a softly sunny afternoon with most attractive light; not easy for spotting bryos, due to the deep shadow, but far more pleasant than cold water drops unerringly finding the gap between hat and collar!
The West entrance to Creech is a track with a limestone base so somewhat untypical mosses for heathland form a sparse turf here, such as Barbula unguiculata, Rhynchostegium confertum and Cratoneuron filicinum. There is also a stand of established woodland at this point, so a range of typical epiphytes occurs, including Hypnum cupressiforme, Isothecium myosuroides, Cryphaea heteromalla, Zygodon viridissimus, Orthotrichum (Lewinskya) affine, Ulota bruchii, Frullania dilatata, Metzgeria furcata and some M. consanguinea. Mature beech trunks hold a dense cover of Neckera pumila, a moss we’d seen last season also on beech. Acid banks in this wooded part of the heath have Mnium hornum, Thuidium tamariscinum, Polytrichum formosum, Pseudotaxiphyllum elegans and a local abundance of the attractive Lepidozia reptans.
As the track progresses onto the heath the calcareous fill disappears, to be replaced by the indigenous clay. More typical heath or grassland bryos appear, including Pseudoscleropodium purum, Dicranella heteromalla, Dicranum scoparium, Polytrichum juniperinum and Campylopus introflexus, along with some C. pyriformis and C. brevipilus. Drier paths and the odd old bonfire site hold mosses such as Ceratodon purpureus, Bryum argenteum, B. capillare, B. bornholmense, Archidium alternifolium and Funaria hygrometrica, with a decaying pine stump providing a niche for a fine cushion of Dicranoweisia cirrata. Hypnum jutlandicum is frequent in the heath but Molinia is rather dominant in this area so bryos are relatively limited.
The wet nature of parts of the heath is reflected by the presence of a scatter of Sphagnum species, including S. compactum, S. tenellum, S. auriculatum, S. palustre and S. subnitens. A broader expanse of wet heath has frequent S. cuspidatum and some elements of more typical mire vegetation including S. papillosum, S. pulchrum and S. rubellum. Liverworts in amongst this Sphagnum community, or on associated wet peaty soil include Odontoschisma sphagni, Kurzia pauciflora, Cephalozia connivens, C. bicuspidata, Calypogeia fissa, C. muelleriana, C. arguta and Cladopodiella (Odontoschisma) fluitans, and a little Aneura pinguis.
Another interesting day, with the fine and softly bright afternoon a pleasant surprise. Rather bleak and colder conditions are forecast for the days ahead….
Creech Heath is a large expanse of lowland heathland in Purbeck, west of the Blue Pool and S of the railway. It is part of the suite of similar heaths all with SSSI, SPA and Ramsar designations, several of which now form the Purbeck Heaths 'super' NNR. Creech is leased and managed by Amphibian and Reptile Conservation, although owned by Imerys, with some active ball clay extraction still, and plenty of evidence of former clay winning.