Thursday, 19 April 2012

Sibthorpia in South Wales

At the end of March I spent a few days in Carmarthenshire and Glamorgan trying to refind historical sites for Sibthorpia europaea Cornish Moneywort. We began around the Brechfa Forest, where Sam Bosanquet was able to show us a population he had visited fairly recently, so we were able to fix a search image in our minds. We then visited a few more old sites, with some success and some failure in refinding Sibthorpia. However, by the end of the day we had also found a couple of new sites. The habitat requirements of Sibthorpia seemed very specific, requiring steep, almost vertical bare mud with seeping water. Almost always associated with Chrysosplenium oppositifolium Opposite-leaved golden saxifrage Sibthorpia is so small and prostrate it could almost be mistaken for a bryophyte. Towards the end of the day we found ourselves driving around lanes, and discovered one new population simply by stopping in a suitable pull-in on a corner, where a small seepage of water comes down the bank. Unfortunately, Sibthorpia is not found every time these conditions occur. 
The bank where the largest population of Sibthorpia was found. Small patches were scattered throughout the area between the two surveyors. Photo: Alison Heath. 
A large dense patch of Sibthorpia. Note that the leaves are generally about 0.5-1cm and so much smaller than any similar species. Photograph: Alison Heath.
A roadside site where Sibthorpia is found on the bank beneath the hedge, especially adjacent to a pistyll or water spout. Photograph: Alison Heath. 

The following day I spent a few hours wading down a river slightly to the south, where Sibthorpia had previously been recorded along the bank. However, no sight of it on this occasion, although as well as the ever-present C. oppositifolium  there were occasional plants of C. alternifolium Alternate-leaved golden saxifrage and a lot of Saxifraga granulata meadow saxifrage. 

The third day was spent in Glamorgan, where Julian Woodman first took us to an open, reclaimed colliery site, where in a complete contrast to the Brechfa sites Sibthorpia could be found in small streams/ ditches running through Molinia purple moor-grass covered open land. Sadly, although we spent a lot of time searching along streams and banks, additional historical sites did not yield any up-to-date findings. 

As we searched, there was much speculation about why Sibthorpia should be so scarce and not found where apparently suitable conditions exist. It seems that it may form a meta-population and so individual populations may become extinct or re-established from time to time. The distribution mechanism is a matter for speculation, with one suggestion being that it is spread on the feet of woodcock, which like to forage in damp woods. However, we thought it unlikely that woodcock would be so frequent in some of the roadside sites. 
Small stream/ ditch through Molinia grassland where Sibthorpia was found in Glamorgan. 

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