Wilverley Plain to Holm Hill, New Forest, Wedensday, 19th June 2013

As part of the New Forest Heathland Lichen Survey, an evening meeting was held to start a survey of the grid square SU2502. We met in the small northern car park at Wilverley Plain at SU256012 at 6.45pm. The day was warmest day of the year so far, lightly overcast and humid, a big contrast to last years summer evening meeting, which was very wet. Attending were Ginny Copsey, Brian Gale, John Norton, Richard Reeves with Neil Sanderson leading. (Note, I experimented with making this a paperless survey, by recording on my iPhone, this worked well, except I forgot to take any photos; the photos in this report were taken on a lunch time dog walk a couple of days latter).

The car park was in an old gravel pit, with interesting parched acid grassland on its banks, it was too trampled for lichens, except in a corner where there was a patch of Cladonia rangiformis. The vascular plant flora was rich and included Heath Pearlwort Sagina subulata and the annual clovers, Trifolium striatum & Trifolium subterraneum. The road verge adjacent had some Hay Rattle Rhinathus minor, which is rare on the open forest grazings. We skirted round the reseed area of Wilverley Plain, a now very rich grassland on former war time arable cultivation of the heath and headed into undisturbed heath.

Still in SU2501, we passed an area of recently mown heath; this is carried out as an alternative to controlled burning on the Forest locally, with the Heather bales used in mire restoration projects. For many features the process is less beneficial than controlled burning, including lichen diversity and regeneration from seed of the heathers. This is for a shared reason; the mowing leaves intact the mat of common late succession mosses and a layer of loose litter. This prevents the germination of heathers and denies the smaller lichens the open hard humus surface they prefer.

Mown heath

Beyond the mown heath we entered grid square SU2502, at first the heath was dense old heather with no lichens. Then on the edge of the plateau (Waymark 2501-01, SU2569 0203) open banks along the track began to support a diversity of smaller Cladonia species, with patches of tall Reindeer Mosses in gaps in the still quite old but low productivity heath. The plateau edges are typical places to find greater lichen diversity; the soils have been impoverished by the finer proportion of the plateau gravel being washed down slope. The bank produced Cladonia uncialis, Cladonia ramulosa, Cladonia grayi, Cladonia subulata, Cladonia cornuta, Cladonia diversa, Cladonia floerkeana, Cladonia furcata, Peltigera hymenina and Placynthiella icmalea. The tall reindeer Mosses in the heath were an object lesson on the perfidious variability of Cladonia portentosa. Here it was at its most confusing, with the gracile form with somewhat curving end branches (Cladonia portentosa f. impexa) casing much confusion with Cladonia ciliata. Fortunately some real Cladonia ciliata var. ciliata was found; in this the end branches are more strongly curved and all orientated in the same direction on a podetia. On Cladonia portentosa f. impexa, although the branches may curve they do not all point the same way.

Cladonia ciliata var. ciliata & Cladonia portentosa f. impexa

We then crossed north over the plateau, which had tall dense heather with scattered Bracken and no lichens, to the opposite plateau edge slope. The upper slope had lower productivity heath on the eroded sands that had been exposed below the plateau gravels, with richer soils on the redeposited head (washed down material mainly originating from periglacial erosion) at the bottom of the slope. We cut along the upper slope, with lichen interest bringing to pick up in glades in the heather and along pony paths. John found Cladonia polydactyla, a common species on lignum but rare in the New Forest heaths. At Waymark 2502-02 (SU2575 0229) a larger open patch produced Cladonia diversa, Cladonia verticillata, Cladonia macilenta, Cladonia crispata, Cladonia squamulosa var. subsquamulosa (the heathland form) and Cladonia cryptochlorophaea.

Further along large bare patches by a wider pony path (Waymark 2502-03, SU2574 0230) were especially rich with the heathland specialists Pycnothelia papillaria and Cladonia strepsilis, more Cladonia verticillata, a little Cladonia phyllophora (NT, NS) and Micarea erratica on flint.

Habitat & the pony path

Round the corner on the slope we found a pony path where a recently eroded rut had been created (Waymark 2502-04, SU2572 0237). Approaching the rut, John found an odd looking Micarea, with piebald apothecia. Under the microscope, this proved to just be Micarea lignaria var. lignaria, which appeared to be parasitised by pycnidia growing on the apothecia, however, the pycnidia were clearly those of Micarea lignaria; odd! Inside the rut the freshest face was dominated by Baeomyces rufus, an early succession species of eroded banks in the heaths, which is absent from older banks with humus build up. Here it was parasitised by the black disks of Arthrorhaphis grisea, a rarely recorded species in the lowlands. There was more Cladonia verticillata, with a couple of fine colonies of Cetraria muricata on the rim. At the upper end of the rut a yellow green crust caught my eye. This was yellower than the common Micarea viridileprosa and the leprose (a lose mass of fungi and algae without a cortex) thallus was composed of visibly larger granules than that species. A dab of C confirmed my suspicions;, the thallus went C + persistent orange, rather than C + fleeting red. This was Micarea xanthonica (Nb, NS, IR), new to the New Forest heaths. This is a local oceanic species, which is occasional in the New Forest old growth woodlands and has been found on peat in the uplands. It was an unexpected find for the New Forest heaths.

Heathland rut

As a break from Cladonia identification, we then had a look at the species rich grassland at the base of the slope. This had species such as Anemone Anemone nemorosa in the Bracken patches, a few still flowering, and Betony Betonica officinalis and Sawwort Serratula tinctoria in the grassier patches. There was a large population of the sedge Carex montana (NS), which could be picked out by its loosely tufted growth form and its yellow green leaves. Also present was Euphrasia anglica, an easy Eyebright to identify on the Forest, due to the abundant glandular hairs. It is listed as Endangered in the vascular plant RDB, although frequent and stable in the New Forest.

Species rich grassland

Finally we circled north east to intercept a hollow way complex (Waymark 2502-05, SU2582 0247). These looked like they were once very good and Richard remembered the area when these hollow ways were more open, but they are now rather over grown by tall heather. They will, however, be opened up by the next controlled burn and recover their lichen diversity. The most open hollow way still had some lichen interest with Micarea lignaria, Cladonia subcervicornis and Pycnothelia papillaria and Rhizocarpon reductum and Porpidia crustulata on flints.

On way back had a brief glimpse of a big bird of prey quartering the ground, the birders decision was 60% Marsh Harrier, 40% Buzzard.

We recorded at total of 28 lichen taxa from the heathland in SU2502 and a CCP index (Cetraria/Cladonia/Pycnothelia index) score of 21, (high quality heathland lichens sites typically scoring over 15).

Then off to the pub, missed food but saw Stag Beetles flying over.

Species list

Download the KMZ file to view route and waymarks in Google Earth, or view as picture below

Addendum further survey on next Saturday (22/6/2013),