Ditchling Common South

One of the recent attendees on BBS SE meetings is Nevil Hutchinson, and he has also joined BBS, so the two of us explored the southern part of Ditchling Common a couple of weeks ago. I only realised afterwards that Jacqui had already visited the tetrad, though as always is the case multiple visits clearly can reap rewards.

Starting off in the north-east corner of TQ31I we spent ages on a little track heading into the common. This was an ideal opportunity to see many common species, including the little acrocarps that grow in that habitat, such as Barbula unguiculata, Didymodon insulanus, Ceratodon purpureus, Funaria hygrometrica and Bryum dichotomum.

Map of Ditchling Common South

Records from Ditchling Common

A few of the oaks dotted around the open space harboured some common epiphytes, and we spent a little while around the small bridge over the stream, where we found a Fossombronia, though it wasn’t fruiting unfortunately. Alongside the stream were some very pale clumps of Brachythecium albicans.

Picture of leaf of Brachythecium albicans

Leaf of Brachythecium albicans

A small pond with willow harboured Cololejeunea minutissima, Fissidens bryoides and Eurhynchium striatum, and an iron drain by the B2112 was the rather surprising substrate for Zygodon conoideus.

Beginning to run out of time, we headed along the track towards Fragbarrow Farm, which turned up some of the most interesting species of the day, including Orthotrichum lyellii, Orthotrichum stramineum and Ulota phyllantha. Even so, there are still a few specimens that I’ve not identified, and they will be heading to Tom in due course.

Picture of Ulota phyllantha

Gemmae-laden tips of Ulota phyllantha

Here’s a question, then: after how many hours visiting a tetrad can you be reasonably sure you’ve got, say, 95 per cent of the species in it?

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4 thoughts on “Ditchling Common South

  1. Brad, that’s an interesting question but the answer must surely depend on where the tetrad is. Some of the large tracts of moorland in northern and western Britain are surprisingly uniform and in the absence of obviously different-looking areas (flushes for example) I would think you could have got 90% of species in a few hours. In a large area of fairly well-recorded mire with associated rock outcrops and heathland I recently recorded 60% of what anyone had ever found there in about 4 hours. Given another 4 hours I could possibly have got to 90%.

    But in SE England the habitats are more varied, more fragmented and usually more difficult to access. In a wood at Framfield which I worked to death, I got to 90% after about 12 hours but the rest took at least another 12 hours, possibly more. I doubt there are more than another few species possible there now though (105 species recorded) so likely to be more than 95% complete. But that was just one small wood and a whole tetrad might still not be at 95% even after a couple of days surveying all the accessible habitats. Then if it included a species-rich site such as Scotney Castle it would add at least a day to the task. So taking a balanced view for an average tetrad I would say the answer to your question was between 12 and 24 hours actual recording in your part of the country but maybe more if you then had to start asking permission to get on private land.

    Tom

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  2. I agree with everything Tom has said here, of course. With so many small species it must be easy to overlook some however often one visits and there will always be inaccessible corners. Good that Brad and Nevill added some interesting records to TQ31A. That is a tetrad that still needs more work.

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  3. Pingback: Ditchling Common Revisited | Sussex Bryophytes

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