enlichenment 101 ~ Hoary cobblestone lichen

We first trekked up the big rock in 1996.  I’d looked at it from far below for nearly eight years.  Until Mark arrived, nearly all of my outings were on horseback and the sheer white limestone cliffs did not beckon.  I always rode out the opposite direction.  Heading out on foot opened a whole new world – it was the advent of my now obsessive explorations into to the tiny world of non-vascular plants.  About once a year we venture to the top of the height that serves as a constant sentinel of our valley.  From high on Easter Rock, I can see a tiny speck of meadow we call home awash in a veritable sea of forest.  Deep snow has been the flavor of the day on some of these hikes.  On other occasions, balmy and breezeless sunshine required lolling around and napping once we reach the top.

It is while lying atop the limestone that I begin contemplating the entire little ecosystem functioning there.  Balance is tricky up on the rock – not just anything will grow on this relatively erosive substrate.  Much of the ancient limestone strata, which once capped the entire Black Hills, are gone, eons of wind and water blowing and rinsing the particles to who knows where.  The cliff-edge, where annually I while away part of a spring afternoon in contemplation, has been retreating steadily eastward.  High and exposed, the microclimate here isn’t always pleasant.  It can be harsh.  There are a few small flowering plants here and there, but soon it becomes quite clear that this is the domain of the lichens.  Time and space – in this case, very near space (the little ‘loup’ that I’ve a habit of carrying in my pocket is an essential tool) reveals the exquisite details of tiny ‘microlichens’ growing on the rock.  A specialized community of lichens makes its home on the exposed limestone surface.  One of the tiny hardscrabble miracles is Hoary cobblestone lichen.

~ Mary

Hoary cobblestone lichen ~ Acarospora strigata

Description: Pale grey areolate crustose lichen with apothecia sunken in the thallus.
Habitat: Calcareous rock. It can be quite successful in harsh and exposed habitats.
Comments: In the Black Hills, Hoary cobblestone lichen is considered rare. Found here and there world-wide, it is most common in the North American southwest.