Friday, 20 April 2012

Bogging sphagtastic

For some reason, I was fool enough to organise a day's outing to the heights of the moor on Saturday, in an effort to learn and improve some identification of Sphagnum mosses - bog-moss; the stuff that makes those fat, hummocky cushions on the bogs that look so invitingly soft, yet mask such decidedly soggy ground.

Accordingly 10 (yes, ten!) of us assembled at Whiteworks, just to the south of Princetown, with the cloud roiling and bubbling up to the south-east and a forecast of possible showers - perhaps a little wintry - to come. We were fortunate enough to have secured the help of Mark, county bryology recorder and Sphagnum enthusiast, and Roy, the other bryophyte expert in the group (the rest of us can probably best be described as anything between enthusiastic amateurs and burgeoning improvers) to guide us through the minefield of mosses.

Setting off over the ridge we were immediately sidetracked by a ruined building which contained a number of interesting (non-Sphagnum) mosses as yet unrecorded in that tetrad, such as Rough-stalked Feather-moss Brachythecium rutabulum. We soon found the enthusiasm to head onwards at a brisk pace, only to hit a patch of wet heath which contained our first Sphagna... a rich, wine-red hummock of Sphagnum rubellum (or S. capillifolium rubellum, depending on who you listen to). This was a nice clear and easy species to get our teeth into: not only red as a glass of port, but with such tight-packed individual plants that it resembled a cauliflower. Less simple was a soft-looking, almost weedy specimen: Sphagnum subnitens. This was much less obvious - more what we were all expecting! A little further down the slope and we bumped into a rather apologetic patch of Sphagnum tenellum, softer and more soggy-looking even than the subnitens. This species almost falls apart in your fingers, but has a characteristic 'lobster-claw' effect to the tips of the branches when you look with a hand-lens.
Sphagnum (capillifolium) rubellum. Like a cauliflower soaked in port. Mmm.

Duly impressed with these three starters, we headed down to the bog itself, across a pale yellow-white mass of last year's growth of Molinia.Almost the moment we hit the flatter ground, we bumped into our fourth species: the depressingly variable Sphagnum denticulatum. This is a fairly key species to know, particularly given its tendency to be found in a wide variety of habitats. A twisty kind of moss with branches that are vaguely reminiscent of cows-horns, the best association I can make to remember it is Desperate Dan's famous cow pies. Even if the Beano was always more my cup of tea as a child... A few paces further and we hit another species again: Sphagnum palustre; brown, long-branched and occurring in great sprawling mats under our feet. At this point we learn that this is typical of a whole tribe of Sphagna, having cells which lift from their leaves, giving a roof-tile effect to the branches when you look at them through a lens.
Sphagnum palustre. Similar to papillosum, but with longer branches. Looks a little less spiky to me, and perhaps - in this case - a bit more ochre.

By this time, the cloud had roiled up sufficiently to start discharging, and a grey hazy veil descended on the hillside to the southeast of us. This approached us steadily until we were caressed by the first gentle drops of rain. Nothing daunted - for are not mosses characteristic of humid habitats in any case? - we pressed on. More Sphagna were found which were treated with some caution by Mark and Roy: these looked as if they might be representatives of Sphagnum inundatum and S. fallax, but Mark's caution won out to the degree that he took samples home to identify with certainty under the microscope. Then another - more definite - species: Sphagnum papillosum. Similar to S. palustre, and with the same roof-tile structure, yet subtly different: shorter, fatter branches, preferring a slightly different habitat.

This is a bit of uncertain Sphagnum. Perhaps there should be a category: Sphagnum confusum, though there's probably already a species with that name. Anyway, this could be fallax, or it could be flexuosum. It doesn't help that it's slightly out of focus too. The darker species is probably S. inundatum, though it could conceivably also be some very denticulatum. Aargh!

Sphagnum papillosum. Short branches, looks pretty spiky in close-up and is quite a brownish-buff plant.

By this time the rain had turned to hail. Hah! Hail. We laugh at hail. We settled down to eat lunches, backs to the wind and hail, watching the hillside opposite gradually turn white. A snifter of coffee later the weather eased, and we gathered our fortitude and set out once again, towards the peak of the bog. We soon encountered Sphagnum capillifolium (or S.c.capillifolium) - a looser and more attenuated moss than rubellum, yet with the same rich wine-red suffusion. Lying in a wet hollow nearby was the next species: S. cuspidatum, which has the unenviable yet memorable look of a drowned kitten when hauled from its watery lair. By this time we were well on a roll, and the return of the hail was little more than a niggly inconvenience. As we tramped across the bog we came to an indicator of good-quality habitat: low hummocks of S. magellanicum, a broad-headed Sphagnum which looks as if it's been dipped in long-dried blood.
Sphagnum (c) capillifolium. Rather longer outer branches to the head (capitulum), but still a wine-red beast.

Sphagnum cuspidatum. Fluffy stuff.

And there are plenty of bryophytes which like to grow on the Sphagnum too: in this case lots of Polytrichum strictum growing on a hummock of S. rubellum

Sphagnum compactum? Or perhaps some papillosum masquerading as compactum?
Our search took us onto the main body of raised bog, where we sought a true Dartmoor rarity: Sphagnum austinii. The only prior record of the species was in 1967, when it was noted as growing in numerous tall hummocks across the northern part of the bog. The hummocks remain, but unfortunately the Sphagnum appears to have long since died out; its mass providing a perfect haven for a number of other species of moss and of liverwort, as well as making a nice dry shelter for voles, judging by the holes dug in the sides. By the time we'd searched across the top of the bog for any trace of austinii the hail had begun to drift several centimeters deep, so reluctantly we gathered ourselves together and trudged back to the cars.
And the final species: a bit of Sphagnum magellanicum poking through the hail.

Growing on the old presumed Sphagnum austinii hummocks were plenty of other interesting bryophytes, including the liverwort Mylia anomala

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