Ashdown Forest woodland bryophytes

Tom Ottley, the bryophyte recorder for Sussex, is currently surveying Ashdown Forest, and I was delighted to be invited to accompany him to look around Hindleap Warren, the outdoor activity centre in Forest Row, near Wych Cross. It is one of the areas of the forest that were first enclosed after 1693 and used for rabbit farming. It heavily wooded, and includes several deep-cut streams, a good portion of which are now somewhat overrun with rhododendron, as well as many old banks and paths. Beyond the southern boundary of the warren is some fantastic bog which we also visited, though I’ll write a separate piece about that and have more of a focus on Sphagnum generally.

It was my first decent bryophyte walk this season, so was a good opportunity to do some revision and better learn the differences between species. This certainly doesn’t cover all the species we saw, and there were plenty of other common and not-so-common plants that don’t get a look in below. Some of the pictures aren’t from the day; I’ve included a few from previous walks.

We kicked off on the banks near the car park, which was an ideal place to compare a couple of common Polytricales. At first sight I again mis-identified Polytrichum juniperinum, which was growing on the ground and the banks. Its leaves have reddish leaf points, and a constriction at the base of the four-sided capsule, borne on a red seta. Uniquely among those we saw, its leaf margins are untoothed (you need that hand lens…). It can apparently also grow in more exposed, drier habitats than the also-common Polytrichastrum formosum, which doesn’t have the constriction, or red leaf tips and the setae are only reddish below, but yellower near the top.

Picture of Polytrichastrum formosum

Bank Haircap (Polytrichastrum formosum)

Picture of Common Haircap (Polytrichum commune)

Common Haircap (Polytrichum commune)

Later in the day we also saw Polytrichum commune, which looks very like Polytrichastrum formosum, but grows in very different places, favouring open, boggy habitats compared with the shady banks of the latter. Polytrichum commune can also grow much bigger, up to 40cm tall, and the two can also be differentiated by looking at their capsules (usually 4-angled with constriction in commune, and 5- to 6-angled with no constriction in formosum), or their leaf attachments (pull off a leaf and look at the shape of the sheath that attaches to the stem: it is square-ish in formosum, and much longer in commune).

Towards the end of our walk Tom pointed out Pogonatum aloides too. It is less common in the south-east, but also occurs on sandy, acid banks. I thought it was a small formosum (it is less than 1cm tall), but the leaves do look a little more aloe-like, and the capsules are pale and cylindrical, rather than having noticeable edges.

Picture of Pleurozium schreberi)

Pleurozium schreberi

Moving on to the feathery pleurocarps, we started off with the red-stemmed Pleurozium schreberi on the ground, with its 2mm long oval leaves with a short double ‘nerve’. I’d mistaken it for the also-common Hylocomium splendens, which also has a red stem and is found in acid grassland, but the latter is bigger, has a more regular branching, and (importantly) the leaves have points and noticeable teeth in their upper half.

Picture of Rhytidiadelphus squarrosus

Rhytidiadelphus squarrosus

The other red-stemmed species we saw was the related Rhytidiadelphus squarrosus, a very common moss that we often see in lawns around here, and on the golf course. Like other species in this genus, not only does it have a red stem, but also distinctly pointy leaves which, in this case, bend back, giving it a star-like appearance.

Picture of Brachythecium rutabulum

Brachythecium rutabulum

The other common feathery ones which I still hesitate over include Brachythecium rutabulum. It is all over the place and is almost archetypally ‘mossy’, though I often think it might be something else. Generally on more neutral soils and some woody substrates, the irregular branches tend to have lighter-coloured tips, and the leaves are nerved (though not the full length of the leaf) with a small pointed tip, and some light folds in the leaves. The brown capsules have a conical cap with a pointy calyptra, and are borne on a rough seta.

Picture of Hypnum jutlandicum

Hypnum jutlandicum

On the ground in woods and on the heath was Hypnum jutlandicum, which is often quite pale, and (like all the Hypnums) has almost nerveless tapering leaves, which are quite strongly curved.

Picture of Hypnum andoi

Hypnum andoi

Looking up on the trees, Tom reminded me of the differences between the other common members of the genus: Hypnum andoi has leaves which almost curve around the stem, making them quite tight-looking as they hang down the trunk. Some of these plants already have capsules, which are rounded with a small point, making them more distinctive compared with its similar relative H. cupressiforme, which doesn’t have capsules yet (and which have a longer point), and has rather more flexuose leaves.

Unusually, we found a yew covered in moss, which looked a bit different from the others and it turned out to be Hypnum cupressiforme var. resupinatum. It looks a bit more silky than the other Hypnums, with leaves more on one side of the stem and sticking upwards. This is the plant that is called Hypnum resupinatum in the Field Guide, but the Census Catalogue has the current name.[1]

Picture of Hypnum cupressiforme var. resupinatum

Hypnum cupressiforme var. resupinatum

Moving downstream, on the shady bank were carpets of the common liverwort Pellia epiphylla. I wrongly assumed that because it had slightly crinkly edges it was P. endiviiifolia, but that occurs on more base-rich substrates. More interestingly, Tom also pointed out a number of more unusual, tiny liverworts on the edge of the path, and around some muddy hollows. One of these was the very small Solenostoma gracillimum (Jungermannia gracillima), mature plants of which have distinctive thickened edges of the leaves.

We also looked closely at the common mosses with long narrow leaves, the Dicranales, though ‘long’ in the context of mosses may only mean 5-10mm. Particularly common on logs was the dark green Campylopus flexuosus, with its rather erect leaves, and very wide nerve relative to leaf. Its leaves aren’t curved like Dicranum scoparium, and they are a bit brown/orange at the base where they join the stem. Finally, C. flexuosus has no hair point in contrast to C. introflexus. As expected, there was also lots of the silky, fine-leaved Dicranella heteromalla growing on the ground and on banks and roots.

Picture of Dicranum scoparium

Dicranum scoparium

Picture of Dicranella heteromalla

Dicranella heteromalla

In the damper habitat closer to the stream was Dicranella rufescens with its red capsules and setae, growing on the damp sandy bank and some stones. The lower part of its stem in particular is also red.

Picture of Dicranella rufescens

Dicranella rufescens

Other species cropped up in the darker, wetter areas by the stream, including Leptodictyum riparium, which was on stone by the stream; it has almost planar nerved leaves, with a short and unusually stubby capsule.

Picture of Campylostelium saxicola

Campylostelium saxicola patiently sitting on my notebook

Probably the best find in this habitat was the rather wispy, tiny and Nationally Scarce Campylostelium saxicola growing on rocks and stones by the stream which periodically get covered by water. No more than a couple of millimetres tall, and with a long wavy seta, Tom first showed me a few of these plants in Broadstone Warren a few months ago; since then he has been finding them in many other similar habitats across Ashdown Forest.

Picture of Campylostelium saxicola

Campylostelium saxicola

Picture of Ulota crispa

Ulota crispa

Finally, we saw a few epiphytes in the group Orthotrichales. These tended to be on trees with less acid bark, and included the common Ulota crispa with its long, linear, nerved leaves, and which is strongly crisped when dry; its capsules are borne just above the leaves, and the mature capsules narrow just before the mouth. By contrast, the common Orthotrichum affine is not crisped when dry, and its abundant capsules are not quite clear of the leaves. Its leaves have recurved margins and a sharp tip, and is the the commonest of the genus on trees. By contrast, Orthotrichum lyellii is much bigger (maybe 3cm tall!) and covered with brown gemmae, making it very distinctive.

Picture of Orthotrichum affine

Orthotrichum affine

Picture of Orthotrichum lyellii

Orthotrichum lyellii

Towards the end of our walk Tom noted a large colony of Orthotrichum tenellum on sycamore. It is more typical of the south west, is smaller and narrower than O. affine, has a longer capsule and hooded leaves, and was also accompanied by O. diaphanum with its distinctive white leaf point.

Picture of Orthotrichum tenellum

Orthotrichum tenellum

I think I now can distinguish the Orthotricales from Dicranoweisia cirrata, which is also epiphytic and grows in cushions; its leaves are very fine with a point and the nerve runs the length of the leaf. They are a bit wavy when damp and then very crisped when dry. It often has capsules, which are on yellowish setae.

So, it was a rather intensive few hours with the bryophytes. There were several that Tom noted which completely passed me by, including many common ones which I’m not familiar with. After a short break we then started to look at the boggy wet heath beyond the bounds of the warren, and I’ll describe that in a future post.

[1] Hill, M.O., Blackstock, T. H., Long, D.G, Rothero, G.P. (2008) A checklist and census catalogue of British and Irish Bryophytes. Available from BBS.

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