Friday, 10 February 2017

Whitecross Green Wood

The liverwort Radula complanata fruiting
WhitecrossGreen Wood Nature Reserve just outside vice county 23 in Bucks was the venue for an informal meeting of six bryologists on Sunday 5th February. Four of us had visited the site late in December when, notwithstanding the hard frost, we had put together a good list of bryophytes and decided the wood deserved another visit. This is a brief account of what we found on this second visit. A full site list can (or will soon) be found under the ‘Local Studies’ section.

Most of the meeting was spent in the low-lying woodland which was planted with Scots pine in the 1960s but that is now being reverted to broad-leaved woodland under the management of the Wildlife Trust. In among the trees we worked up a good list of the woodland bryophytes one would expect to find in the area, with a range of Orthotrichaceae and the liverworts Frullania dilatata, Radula complanata and all three commoner Metzgeria species (M. consanguinea, M. furcata and M. violacea) on trees and typical ground mosses such as Eurhynchium striatum. On our previous visit we’d also found several colonies of the tiny epiphytic liverwort Cololejeunea minutissima growing on sallows and willows.

The highlight of the meeting was a gorgeous colony of Leucodon sciuroides found in an area of recent felling. This is a large and uncommon moss that is always a pleasure to find. Chainsaw-wielding Wildlife Trust staff had helped us in finding it, having felled the ash limb it was growing on, but one worries about the future of the colony as a result. The plants sported a great many vegetative propagules in the form of bud-like compact branches, so we hope it spreads about the wood if it isn’t already present elsewhere.

A colonoy of the robust pleurocarpous moss Leucodon sciuroides growing on a felled ash limb (left). The close up of the shoots on the right shows the tiny bud-like branchlets in the axils of the leaves which serve for asexual dispersal.
The broad rides provided further diversity, with bryophytes in the ditches, on exposed clay on the banks and in the grassland. In the ditches was found a small patch of the big liverwort Plagiochila asplenioides, where in a similar habitat on the previous meeting we’d also found the liverworts Calypogeia arguta and Riccardia chamaedryfolia. The exposed clay supported an abundance of Fissidens, with the common F. bryoides and F. taxifolius, and the less common F. incurvus and the tiny F. exilis

A close up of the Platygyrium repens colony showing the characteristic tight, drumstick-like clusters of deciduous leaves at the tips of the shoots (centre) and the rarely produced sporophytes. The height of the shoots is 2 or 3mm and these grow in rather close silky-looking wefts of a dull greeny-bronze colour.
On the previous meeting the scarce mosses Herzogiella seligeri and Platygyrium repens had both been found and these were again much admired. The colony of the latter by the pond in the reserve is certainly the largest I’ve ever seen, smothering many trees, mostly crack willows, in that very humid area of the reserve. It is of added interest because this year it fruited abundantly, a very rare occurrence for this dioecious moss. P. repens was also found in small quantity on an oak tree near to where the Leucodon was seen.

Fruiting Thamnobrum alopecurum
Reaching a point of diminishing returns we clapped on our bryological blinkers and headed up hill to the drier more intact ash woodland (Oriel Wood) to see if we could find anything different. With all those big ash trees we had expectations of Anomodon, Homalia and Neckera complanata but were rather disappointed, all the tree bases and the ground being covered in Thamnobryum alopecurum. Some of this was fruiting, however, which happens infrequently enough to have drawn admiration. There was a small amount of typical epiphytes of ash trees, such as Bryum moravicum, Orthotrichum stramineum and Zygodon conoideus, but nothing noteworthy. We headed back along the long main ride and reflected on a rewarding day spent bryologising.

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