Lichens

Thursday's Guardian Country Diary explores the wonderful world of lichens that are the brightest objects on moorland in winter. Lichens like .....

...... this delightful Cladonia diversa (?), tipped with what looks like scarlet sealing wax. Those red tips are the apothecia, where microscopic flask-shaped asci shoot their fungal spores out into the breeze. To form another lichen they need to land close enough to the correct alga for the two to form a symbiotic union and develop into a lichen.

This is the moorland described in the Country Diary - a high, windswept path over Birkside Fell above Blanchland, in the Derwent valley on the Durham-Northumberland border. The high rainfall means that nutrients are rapidly leached out of the sandy soil. The area to the right is grouse moor, which from a distance seems like is a sea of dull brown vegetation, until .....

.... you look at what is going on at grouse-eye level, under the canopy of gorse bushes. There, at this time of year, the lichens are at their best and the mosses are actively growing too.

There's a wide range of lichen form and colour. I think this is Cladonia macilenta (?)

..... this looks like Peltigera lactucifolia (?)

.... and this, looking like a forest of tiny golf tees, is Cladonia pyxidata (?)

N.B. the (?) after the specific names mean that these are tentative IDs - I need to check them more carefully to be certain!

A Lichen with Teeth

We found some very fine specimens of dog lichen Peltigera sp. when we were out  walking at Shittlehope Burn at Stanhope in Weardale this morning. I've often wondered why it's called dog lichen - I've found one or two references that suggest that Linnaeus gave it the Latin specific epithet caninus because he saw some resemblance to a dog in its shape, which I find hard to see, unless it relates to the menacing tooth-like structures, called rhizines, on the underside of the thallus.

The arrangement of the rhizines, which are extensions of the fungal part of the symbiotic partnership between alga and fungus that constitutes a lichen, are key identification features and as soon as I can get my hands on a lichen field guide I'll try to identify the species more accurately.

Some Peltigera species contain cyanobacteria that fix nitrogen in the symbiotic partnership, so the organism then has its own in-built nitrogen fertiliser supply and plays a part in the cycling of nitrogen in ecosystems.