Epiphytes on the move

I always like to find Frullania species when I'm out bryologising. Both Frullania dilatata and Frullania tamarisci are fairly common species. I just like the colour.

Frullania tamarsci near Blakeman's Law

In North-east England, most bryophyte epiphytes become more common the further west you go. Areas with high rainfall, especially sheltered, humid gorges are generally the best places. Many species are also sensitive to certain types of air pollution and as a result large areas of eastern England have lost most of their epiphytes. Nowadays the air is no longer polluted from as much coal-burning as it was in the past. It has taken a few decades for epiphytes to recolonise formerly heavily polluted areas, but in the last 10 years or so several species have begun to recolonise eastern areas at a dramatic rate.

In the south-east of England and East Anglia, this phenomenon has been fairly well studied and documented, as there are quite a few active bryologists down there. Up here, we have more bryophytes but bryologists are very thin on the ground and recent recording has been so patchy that we just don't know yet which species are recolonising and how fast. It seems like some of the species showing the greatest recent increases in the south are not so prominent here, at least yet. On the other hand we probably have other species that are recolonising our area, that are still rare in the south.


Ulota phyllantha at Brown Hill

About 10 days ago I found lots of Ulota phyllantha on willows and rowans in a sheltered valley within Kielder Forest south of Stonehaugh. This is quite uncommon in Northumberland, but I found it on lots of trees in various places within about a mile of where I took the picture. I've no idea if it has been there a long time or if it has recently recolonised. Andy McLay recently found it in Co Durham - the first record there for over 100 years. I told him I wouldn't be surprised if he found some more and a couple of days later he found some at another site.


Orthotrichum pulchellum at Brown Hill

Orthotrichum pulchellum is one of the species in the south that has shown a big recent increase. I've been puzzled why we haven't found more of it up here. There was a big population of it on about 5 or 6 trees in the same valley south of Stonehaugh. For an Orthotrichum it is quite distinctive: it is the only one whose leaves curl up when they are dry; it has a very neat overall appearance; it is always quite small; the base of the calyptra usually has dark dots all round it; and the peristome theeth are orange.

Hopefully it will start turning up now in some other new sites.

John

A mountain stream in Regent's Park??

The shot below shows a water feature in the 'nature study' area of Regent's Park in central London. On a recent bryophyte survey we did for the park this was one of the few habitats we found with a well-developed bryophyte community. The sheltered water feature creates a suitable humid environment for several species that otherwise occur only sparsely in the area.

However the biggest surprise was finding Racomitrium aciculare sitting on rocks by the 'stream'. This species has never been recorded in Middlesex before and is very uncommon in south and east England as you can see from this distribution map from the NBN website.

In the north and west of Britain you can almost gaurantee to find it on rocks by any upland stream, but this habitat is absent from most of lowland Britain.

The neat round cushions with the white hairs sticking up in the picture above are Grimmia pulvinata which is a very common species on rocks and walls everywhere. Racomitrium aciculare is the more straggly dark green plant in the middle of the top of the picture, with a few more shoots on the top right.

The main focus of the survey was to look for bryophyte epiphytes (plants that grow on trees). These were fairly sparse and mainly confined to a small number of species. Many epiphytic species cannot live in areas with high athmospheric pollution. In recent decades particulate air pollution associated with coal fires has almost gone and as a result in recent years several epiphytic species have been sucessfully recolonising areas they have been missing from for a very long time. However most truly urban areas still have relatively few epiphytes.

The picture above shows the most common type of epiphyte community we found, comprised mainly of the lichens Physcia adscendens and Xanthoria parietina, with a little of the moss Orthotrichum diaphanum. Most Orthotrichum species are epiphytes and Orthotrichum diaphanum is the one that is most tolerant of air pollution.

On a small number of trees the bryophyte element of the epiphytic community was more developed but it usually consited of just Orthotrichum diaphanum and Rhynchostegium confertum. Interestingly, their were occasional cushions of both Tortula muralis and Grimmia pulvinata on the trees. These species normally grow on walls or rocks and only rarely grow on trees, but something about the tree habitat in London makes them behave differently.

There are many London plane trees in London parks and at first glance these would seem to be unpromising habitat for epiphytic species as the trees shed their outer bark in small patches very regularly. This habit allows the trees to cope with polluted areas better than most other tree species as every time the bark is shed it results in a fresh clean new bark free from grime, helping the tree to breathe easier. It turned out that London plane is in fact the best tree species for bryophytes in central London (apart from elms which are much less common). The epiphyte community is often fairly well developed on the base of the larger trees where the bark is no longer shed so regularly. The texture and chemistry of the bark must make the suface more suitable for epiphytes than the other tree species.

John

Epiphytes in a Northumberland wood

A couple of weeks ago I went out hunting bryophytes with Doug McCutcheon and Ian Craft. We were trying to relocate a rare moss that Doug had found a few years ago in the woods between Bellingham and Hareshaw Linn waterfall. The woods were fairly ordinary at first with mainly the usual common species present. When we got about half way up we started to find more interesting species. The epiphyte communities were especially interesting, particularly close to the stream where the athomosphere was most humid.

As a rule in Britain, the further west you go, the more diverse the epiphytes. There are many species that have an extreme western distribution in Britain. So unsurprisingly the best places to find these species in Northumberland are probably in the extreme west of the county. The valleys of the South Tyne and Irthing are probably well worth exploring.

But the woods at Bellingham had some very nice uncommon species. Ian took all of the photos below. The first one is a nice shot of Frullania dilatata which is a common enough species but very noticable and attractive when it is this dark red colour. There is a tiny bit of Radula complanata (the pale green one) poking in at the top of the photo. This is also reasonably common but usually grows in fairly good quality habitat for epiphytes.

This little cushion-forming moss growing on the twig is Ulota drummondii. Most Ulota species nearly always grow on twigs. This is a fairly uncommon species in Britain and in England it is very uncommon and now more or less confined to Northumberland and nearby bits of Cumbria and Durham. I had never seen it before but Doug has found it several times in Northumberland and was able to point out its distinguishing features to me. The lower parts of the shoots have a reddish tinge and the peristome teeth are white and stick out.

By the stream on several trees there were lots of patches of this Metzgeria (a small thalloid liverwort). Unlike the very common Metzgeria furcata, this species has attenuate (narrowed to the tip) branches that stick out and are covered with tiny green gemmae (vegetative propagules). Doug and I both brought some home to check which species it was. Doug's plant was Metzgeria fruticulosa but mine looked more like Metzgeria temperata. I've sent this away to be checked by the BBS referee for Metzgeria. If it is right then its only the 2nd record for Northumberland for this species, the first one was only last year from a tree next to the South Tyne.

There are two epiphytic lichens (which Doug identified) in this shot. The one on the right with the light brown/reddish bits at the end of the thalli is Peltigera praetextata. Clinging closer to the tree and occupying most of the rest of the photo is Protopannaria pezizoides. This was a stiking species forming big patches, the red bits looked a bit redder in real life. Doug was very excited to find this as it is fairly rare, mainly occuring in north and west Scotland and had not been recorded from this wood since 1897! There was at least one other epiphytic lichen that we saw in the wood which is a good indicator of long ecological continuity in woodland.

Britain probably has more variety in its epiphytic communities than any other country in Europe (maybe apart from Norway and Ireland), but they get virtually zero attention in the conservation world. One of my 'big ideas' is to some day do a detailed study of epiphyte communities accross the country. As far as I know the type of comprehensive study I have in mind has only been done once before by JJ Barkman in Holland. But before I can embark on something so ambitious I really need to develop my ID skills more. After putting a lot of time in over 5 years I'm starting to feel like I'm getting there with bryophytes, but while I'm still learning them I just don't have enough room in my brain to cope with lichens also.

However, watch out for my tome on British Epiphyte communities in about 40 years time!