Monday, 30 November 2015

Riverside Anomodon

I usually associate Anomodon viticulosus with limestone, and it is certainly most abundant in VC35 on the Carboniferous Limestone of the lower Wye Valley and at lower altitudes around The Blorenge, but there are also plenty of colonies on riverside trees here.  I assume that this results from silt deposition, also favoured by Orthotrichum sprucei.

A riverside patch of Anomodon viticulosus, and the species' distribution in Monmouthshire, with riverine populations (ringed in yellow) on the Usk, Monnow and Trothy, and limestone populations (ringed in green) around the coalfield, in the Wye Valley and near Usk.

I saw a large patch of Anomodon on the base of a mature Sycamore by the River Usk just upstream of Newbridge-on-Usk on Saturday, during my first (very brief) bryo-recording walk of the season.  Orthotrichum sprucei was frequent, including on a Field Maple by the lane above the river (about 15m above the usual water level), and I also found a small population of O. rivulare (much rarer by the Usk than its relative).  Leskea and Syntrichia latifolia were abundant, but Plagiomnium rostratum was remarkably rare and I found no sign of Mnium marginatumM. stellare, Dialytrichia mucronata, Tortula subulata or Myrinia pulvinata (all present but rare alongside Monmouthshire's rivers).  I was also surprised not to spot any Hennediella stanfordensis.  It would be a very interesting project to compare south Wales' varied riverine bryophyte floras.


  1. I think that's a great idea Sam. Between us all we cover a significant number of South Wales' rivers and we probably have quite a lot of information already. Even if our comparative data was just lists of species for each river, with semi quantitative records of abundance (e.g. DAFOR), it would be interesting. Leskea is fascinating, we've searched hard for it in NPT and, although there is some, it certainly couldn't be described as abundant as you find it on the Usk. Homalia, which is frequent to abundant on the river Neath, appears to be rather scarce on the Tawe. We see more Syntrichia latifolia on Tarmac than on NPT's rivers!

  2. The Glamorgan map shows Anomodon has not been recorded away from the Limestone areas. It's a very distinctive species, so I doubt it's been overlooked, perhaps insufficient base-enrichment in the rivers/silt? Both the Tawe and Neath Rivers seem less silty than the Loughor which might explain some differences, but yes that would be a fascinating area for analysis when we have more data. I've only skimmed the surface with recording along the Loughor and Tawe and its tributaries, but once the Swansea tetrads are completed (hopefully this winter as only about 10 more left) it's been my intention to do more riparian recording.

  3. I've only seen riparian Anomodon once, a smal patch on Ash roots by the Taff in Cardiff (ST1480). See

    I agree that a comparison of the bryo floras of our rivers would be an excellent project. It would be nice to have some minimal level of sampling on each river - perhaps visiting a stretch of riverbank in a certain number of tetrads - to avoid too much bias towards those where we've done most recording. I'm guessing that the central Glam rivers (Ewenny, Ogmore etc) are very under-recorded.

    As an aside - for some inexplicable reason Anomodon is my favourite moss!

  4. The river by Old Castle Down is very base-rich and interesting, judging from my only brief visit.

    There might be a potential tie-in with the NRW river monitoring team, who are recording regularly on many rivers but have their collection restricted to the regularly-inundated area (so they aren't looking at the most interesting areas for bryophytes). They will also have info on water quality, silt etc.