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Local Meetings of the BBS

Cambridge Group 2002/3

 

 

Meetings of the Cambridgeshire Group are devoted to recording for the proposed new bryophyte flora of VC 29. We often try to visit a range of habitats in one or more 5-km squares, although sometimes we concentrate on a single, larger site.

The 2002-03 season started at the Ouse Washes on 6 October 2002. Until recent years the Washes, a famous bird reserve, has been bryologically unknown, partly because the extensive tracts of grassland are not the most inviting of habitats, and partly because they are flooded for most of the winter. As we had hoped, this meeting was held before the winter rains, and we covered ground in TL48NE, 58NW and 59SW. Aphanorhegma patens was a feature of ditch sides and poached, peaty ground in all three squares, growing on one newly-cleaned ditch bank with tiny, Riccia-like rosettes of Marchantia polymorpha 5-10 mm in diameter. Bob Finch detected Amblystegium humile amongst Water Mint (Mentha aquatica) on winter-flooded ground, and Robin Stevenson spotted fruiting Scleropodium cespitans on willows on the railway embankment that crosses the Washes.

By the next meeting, on 19 October, the landscape was no longer so dry. We met at Floods Ferry to visit one of the randomly selected arable survey tetrads and adjacent fenland ground in TL39NE and 39SE. The two arable fields we surveyed were on base-rich silt (pH 7.9 and 8.1) and both provided Microbryum floerkeanum, accompanied rather incongruously by Ditrichum cylindricum at the pH 8.1 site. The owner of the latter field, returning to his farm with a Range Rover full of pheasants after a good morning’s shooting, greeted us with benign amusement.

On 3 November we visited Bottisham Hall (TL56SE and 56SW), by kind permission of Mr Jenyns, descendant of the noted 19th century naturalist who lived there in the 1820s and 1830s. As is often the case, the parkland produced a varied list of species without any really notable finds. The final excursion of 2002 was to Steeple Morden, on the chalklands at the southern edge of the county (TL23NE, 24SE and 34SW). Eurhynchium megapolitanum was fruiting in the churchyard and then seen in abundance on short, mown trackside turf leading to a chalk pit at Morden Grange. The old, wooded spoil banks of the pit provided some characteristic chalk species, including Microbryum curvicolle, M. floerkeanum, M. rectum, Seligeria calcarea, S. calycina, Tortella inflexa and Leiocolea turbinata, as well as frustratingly sterile plants of Aloina and Weissia.

We started 2003 in deepest fenland on 11 January, a day on which the frost melted just sufficiently to permit bryology. The station yard at Shippea Hill, some farm buildings and a stubble field provided a basic list for TL68SW, the most interesting find being Riccia fluitans amongst Least Duckweed (Lemna minuta) on the bank of the River Lark. Moving on to 68NW, we at first found it difficult to find anywhere to bryologise and were driven to ask permission to search an asphalt drive and garden (it was grudgingly granted, and we were kept under close observation until we finished by a gentleman who charmingly observed that if we had time for this sort of thing we must be less busy than him). Fortunately, a track led us to Six Acre Plantation, where the abundance of Eurhynchium praelongum immediately suggested that the peat was acidified, later confirmed by the presence of swards of Mnium hornum and a pH reading of 4.1. Elders on the north side of the Plantation provided Cryphaea heteromalla, Orthotrichum tenellum, Syntrichia laevipila and S. papillosa. We returned to the cars, listening to the calls of wild swans in the nearby fields and satisfied that we had done rather well in what must surely be some of the least productive bryological terrain in Europe.

A private shoot/nature reserve in disused gravel pits at Hauxton, TL45SW, was the venue on 26 January. We failed to refind Dicranum montanum and D. tauricum, both seen on our last visit to the site in 1977. However, we recorded 58 species, including both Brachythecium mildeanum and B. salebrosum, and, most remarkably, a 20-metre long colony of Climacium dendroides in a goose-grazed sward at the edge of one of the gravel pit lakes. This has previously been recorded in the county as a rare plant of undrained fenland and ancient woodland, never as an obvious recent colonist. The colony was sufficiently vigorous to be first detected by our non-bryological friend Philip Oswald, who was leading the party.

We were lucky to have Oliver Rackham to guide us round Hayley Wood (TL25SE) on 8 February. He led us to the area where the bodies of oaks killed by caterpillar plagues in the 1920s still lie on the ground, their dry, decorticated trunks with attached branches still remarkably intact after 80 years. We refound Nowellia curvifolia, discovered on these logs in 1962 and growing with few associates except Dicranum tauricum and Hypnum cupressiforme. The rotting wood flora was well developed, and other uncommon Cambridgeshire species included Campylopus flexuosus, Tetraphis pellucida and Lepidozia reptans. We paid our respects to the tiny colony of Lejeunea cavifolia in the wood, known since 1968 on the base of a single ash tree, and then found all three Pellia species on the boulder clay rides.

On 23 February we looked at swampy woodland beside the River Snail at Fordham (TL66NW and 67SW). Bob Ellis and Mark Hill found Plagiomnium elatum at only its third extant site in the county, and Kevin Walker spotted P. undulatum in fruit. Although we are now accustomed to finding Syntrichia ruraliformis in inland habitats, its presence as an epiphyte on ash extended its known habitat range in our area.

Ickleton church (TL44SE) in the southern chalklands of the county was the rendezvous for the next excursion, on 8 March. Mark Hill spotted Grimmia trichophylla in quantity on the calcareous coping stones of the boundary wall as we arrived, and Didymodon nicholsonii on shaded tarmac in the village. We had lunch in a disused chalk pit on Coploe Hill, a former site for Thuidium abietinum. The theory that this species had become extinct in Cambridgeshire, propounded by Mark over lunch, was disproved soon afterwards when Bob Finch found a few stems where we had been sitting! Simon Damant found Tortula vahliana around the edge of the pit.

The early spring drought had begun to hinder bryology by 23 March, when we visited Dullingham (TL65NW). With the help of friends from the Norfolk and Suffolk Group, we were able to get a good list from Marmer’s Wood, a small ancient wood in which many of the scarcer bryophytes were apparently very uncommon. Scleropodium cespitans was found by a nearby pond and Weissia longifolia var. longifolia in an adjacent stubble field. We finished the day on the wooded section of the Devil’s Ditch that runs through this square, ending up with the very respectable total of 85 species.

The final excursion of 2002-03 was to Wicken Fen (TL56NW, 57SE and 57SW) on 5 April, a fortunate choice as by now most sites in the county were very dry. An impressive feature of the fen carr was the frequency of Orthotrichum pulchellum, first recorded in VC 29 at Wicken in 1990 and now thoroughly established here in this habitat. Frullania tamarisci, found by Bob Finch as a single patch on a sallow trunk, was new to VC 29 (if the unlocalised 18th century records are discounted). Although many of the calcifuge mosses which colonised the fen carr in the 1960s and 1970s are no longer present, we refound four of the five Sphagnum species recorded from the site and added two more: S. denticulatum, found by Bob Finch, and S. russowii, detected in a mixed tussock with S. subnitens by Mark Hill. It was nice to end a productive season on such a high note.

C. D. PRESTON

 
 
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