April Tree-following—about that Lichen

Several days ago, we headed off to visit the trees I'm following this year. It was a warmish sunny day that felt like spring, finally. And it was very windy, as is often the case in spring.

The two Rocky Mountain Junipers were looking good. The midday light showed their difference in color. The darker tree is the one with "berries" (fleshy cones) on the leeward side. Almost all are yellow. Two seasons are needed for berries to mature. Last year must have been a good one, given all the yellow berries. If the experts are right, this year we will watch them turn blue black.

With so much wind, sharp closeup photos were impossible.

Last month I included photos of a lichen that is really common on the ground in this area. Several readers responded with id suggestions and information—thanks!

Mystery lichen in March.

You probably know that lichens are symbiotic beings. That puts you are ahead of the great botanist Carl Linnaeus, who considered them “poor peasants of the plant world”. Wrong, Carl! But of course that was nearly three centuries ago. We've since figured out that lichens are not plants but rather composite organisms—a fungus and an alga or a cyanobacterium living tightly integrated lives. See Wikipedia's very interesting lichen page about their ecology, how they grow, their long evolutionary history, and the problems they cause when we try to classify them :) For a more philosophical view, try Lichens and the Meaning of Life.

The lichen that is so common in the eastern part of the Laramie Basin is ...  (fanfare) ... Tumbleweed Lichen! That is sooooo perfect for our windy world. Tumbleweed Lichen is a vagrant lichen, also an apt name. Instead of attaching to a substrate—rock, log, fence, etc.—it hugs the ground until wind sends it traveling again.

Our Tumbleweed Lichen is probably Xanthoparmelia camtschadalis or maybe X. chlorochroa. Seven Xanthoparmelia species occur in Wyoming and they're hard to tell apart. X. camtschadalis is common east of the continental divide, which is where Laramie is located.

The junipers I'm following grow in dry sagebrush grassland on thin rocky soil developed on limestone (at or not far below the surface)—harsh conditions, but Tumbleweed Lichen obviously does well here. Coverage ranges from small patches here and there to extensive ground cover, especially on the windward side of sagebrush, grass, and other plants.

Note penny on right, for scale.

Pale green patches at base of plants (lower right to mid left) are lichens whose tumbling was stopped by sagebrush and grass.

Tumbleweed Lichen and Pricklypear Cactus.

In some places, Tumbleweed Lichen dominates the ground cover.

Last month I predicted Easter Daisies (Townsendia) would be blooming now, but I was wrong. The daisies know better. In fact, we woke up to snow this morning.

Easter Daisies wisely waiting for spring.

Sources

Thanks to Judy vA for the articles included here. She met these vagrant lichens in her yard when she lived in Laramie. Thanks also to Jozien and Lysandra for id advice via iNaturalist.

Perry, Tyrell. 2018 (Winter). "What are Lichens?"  Barnyards and Backyards. U. Wyoming, College of Agriculture. PDF

Popova, Maria. 2023 (Mar 25) Lichens and the Meaning of Life. The Marginalian.

Seeing the Craton

Granite quarry near Milbank, South Dakota, in the southwest part of the Superior Craton.

"Craton" comes from the Greek word κράτος, meaning strength.

Seeing the Craton 

Northeast South Dakota, sculpted by glaciers,

landscapes so young, almost infantile,

ice melted just 12,000 years ago.

Glacial floods scoured a deep oversized

valley for the Minnesota River.

I went there to see the craton.

Craton—aged worn-down but strong

rocks hinting at what they once were:

volcanic, sedimentary, intrusive

2.6, 3.5, maybe even 4 billion years ago.

Older even than plate tectonics—

mad dance of Earth's giant plates

recycling crust and leaving none

older than ca. 2 billion years

except for cratons.

Cratons, why are you still here?!

You reside on every continent

yet we know so little.

Perhaps these elderly cratons

wear exceptionally thick undercoats

donned before tectonic chaos began,

back when mantle was hotter

solidifying into stronger threads.

Will they ever tell us?

"cratons are like great-grandmothers at family gatherings, while younger crust moves excitedly around them, they sit quietly, occasionally remarking on how different things were when they were young." Simon Wellings, Cratons – old and strong

2.6 billion-yr-old Milbank granite: brick red feldspar, gray smoky quartz, black biotite mica.

Milbank granite holds a high gloss polish (note reflections); Dakota Granite offices.

Inside the Milbank Chamber of Commerce building.

Old quarry, now accessible to the public (45.2085101 -96.5168962).

Sources

Frost, CD, et al. 2023. Creating Continents: Archean Cratons Tell the Story. GSA Today 33.

Kirk, K. 2023 (March). Dakota Mahogany: Core of the Continent. Natural Stone Institute.

Paul, Jyotirmoy. 2021. Cratons, why are you still here? Eos, 102, 25 March. 

Wellings, S. 2012 (December). Cratons – old and strong Metageologist