At the weekend, we went for a walk in Haugh Wood, which is at the top of the Woolhope Dome just south east of Hereford. It is managed by the Forestry Commission and a good portion of it is conifer plantation. Even so, it has SSSI designation, and is a nationally important site for invertebrates, especially the butterflies and moths. One habitat that isn’t mentioned in the SSSI citation, though, is the tufa bog, in which we found a lovely range of unusual species in far too short a time, so will have to go back and spend some more time exploring it properly.
Tufa is a form of limestone, which is created by the precipitation of carbonate minerals from water at ambient temperatures (ie not from hot springs etc). Interestingly, as Porley and Hodgetts note, research has shown that tufa formation is not always a strictly chemical process; some mosses actively promote carbonate deposition as a result of photosynthesis, so the resulting rock owes its formation, at least in part, to bryophytes, the older stems of which eventually get encased in limestone and die, while newer plants continue the process. This results in the formation of a very porous rock.
The main tufa-forming bryophytes include Palustriella commutata (Curled hook-moss), a gorgeous-looking pinnately-branched pleurocarp with lots of red tones and strongly recurved leaves, and Eucladium verticillatum (Whorled Tufa-moss), which was very heavily calcified. Its lanceolate leaves were often colourless, with discrete chlorophyll-filled patches, and have a toothed border. Other tufa-formers we found were the liverwort Aneura pinguis (Greasewort), plus the mosses Hymenostylium recurvirostrum (Hook-beak Tufa-moss) and Bryum pseudotriquetrum (Marsh Bryum). However, the site certainly includes many other interesting species (including Meadow Saffron (Colchicum autumnale) as well as a diverse range of molluscs), and it will certainly repay a more extended visit.
A related tufa bryo-flora was also reported a few miles to the north-east near Bromyard by the Border Bryologists three years ago, and tufa is now designated under the EU Directive on Habitats and Species. One thing I haven’t quite figured out yet is where this particular boggy spot fits in the National Vegetation Classification; there are two communities that look similar to this at first sight, M37 and M38, though they both seem rather more montane than this part of Herefordshire. A little more investigation is in order….
- “Haugh Wood SSSI citation.” Natural England. Web. 25 August 2014. <http://www.sssi.naturalengland.org.uk/citation/citation_photo/1004355.pdf>.
- Shardlow, Matt. “A seemingly uninspiring wood surprises with fritillary delights.” The Guardian, 12 June 2013. Web. 25 August 2014. <http://www.theguardian.com/environment/2013/jun/12/haugh-woods-butterfly-rare>.
- “Tufa.” Wikipedia. Wikimedia Foundation, 25 April 2014. Web. 25 August 2014. <http://en.wikipedia.org/wiki/Tufa>.
- Porley, Ron and Nick Hodgetts. Mosses and Liverworts. London: Collins, 2005. 273-274. The New Naturalist Library.
- Pentecost, Allan. “Moss growth and travertine deposition: the significance of photosynthesis, evaporation and degassing of carbon dioxide.” Journal of Bryology 19.2 (1996): 229-234. Web. 25 August 2014. <http://www.maneyonline.com/doi/abs/10.1179/jbr.19188.8.131.52>.
- Lawley, Mark. “Border Bryologists 2011.” Field Bryology 106 (2012): 70-72. Web. 25 August 2014. <http://rbg-web2.rbge.org.uk/bbs/activities/field%20bryology/FB106/FB106%20Border%20Bryologists.pdf>.