Water! (tree following in July)

We’re having a wet summer here in normally-sunny Wyoming.  Field botanists sit in soggy tents, waiting.  Fire lookouts sit in their towers reading book after book in fog, mist and rain.  Impassable dirt roads stay impassible as plants grow, bloom and go to seed, unobserved.  I come home to a yard that's a jungle and too wet to mow except that … 

This no longer applies.  I’m retired.  But I haven’t forgotten.

Those memories were vivid this morning.  I needed to check my tree, as the monthly gathering of tree-followers is upon us.  But it was raining again.  So I rounded up my anorak, inexpensive camera and field assistant, and headed out.

I hoped with all the rain there would be water in the dry canyon where my willow grows.

Willow Canyon is upstream from the notch on the right skyline.

Sure enough – in the normally dry wash about a quarter mile below Willow Canyon, a creek was flowing out toward the prairie (above).  Further upstream it ran over limestone outcrops. The drought-tolerant plants in the cracks had their feet in water.

Limber pine (Pinus flexilis) in shallow water – barely visible as slightly darker limestone.

Gumweed (Grindelia squarrosa) had its head just above water.  The creek must have been higher earlier … there's debris hanging off the flower head.

The field assistant was extra happy with the pools.

I reported the exciting news and soon additional recruits arrived.

We reached Willow Canyon – the creek was flowing there too.  Fortunately it wasn't raining, but I still had to wear my anorak because the mosquitos were so thick.

Willow is on the left – the slightly shorter tree against the cliff, between two junipers.

The willow grows where a side drainage meets the canyon, sending water down off the rim.  In fact, this side drainage was providing all the water for the creek below.  The main canyon upstream was dry.

There was even a sizable pool at the base of the willow.  Today this looks very much like willow habitat!

Willow nook a month ago.

Willow nook today.

The little waterfall was well hidden.  But I climbed around just east of the willow and recorded singing water falling from sky to pool.

North of the canyon we followed the creek downstream to the rim.

The creek runs over limestone pavement.

Getting close – bright green patch between two junipers upper left is top of willow.

Looking for kitties in the lush canopy (this is the American pussy willow, Salix discolor).

The creek at the canyon rim.  But it doesn't jump off here.

Instead, it runs into a crevice to become the waterfall below.

How nice that Nature provides such interesting things to ponder!

You should!  Read more about tree following here.

Selenium & the Prince’s Plume – an unfinished tale

Did an errant prince from days of yore in search of El Dorado¹ drop his helmet?

I thought this might be the case ... I was in the right part of the country.  But then I walked closer and saw that the glowing yellow mass was an herbaceous plant.  It was over a meter tall, with a dozen stalks, and was covered in hundreds of yellow buds and flowers.  A multitude of insects crawled, flitted and otherwise wandered through the yellow paradise – a scene full of life.

The many critters were so active that it was hard to capture them in photos.

Was this a healthy garden, a lush mountain meadow, a well-watered stream bank?

Not at all.  It was a high desert in western Colorado.

And as it turned out, the yellow-flowered plant was indeed a prince’s plume! – Stanleya pinnata.  It grows on arid sites in the western USA.

This prince's plume has trapped a tumbleweed.

Prince’s plume is a member of the mustard family (Brassicaceae), and like most mustards it has flowers with four sepals, four petals, six stamens and a single pistil – all yellow in this case.  There also are four nectar glands per flower – probably why there were so many insects about.

The long exserted stamens are dramatic!

After fertilization, the ovaries elongate to become narrow spreading siliques containing small seeds about 2 mm across.

In the mustard family long narrow capsules are called siliques.

Stems and leaves of prince’s plume are a distinctive waxy bluish-green.  In subspecies pinnata, the basal leaves are deeply lobed (upper ones are entire).

A pinnately lobed basal leaf.

I was impressed to find this tall fecund herbaceous perennial in such an arid environment – the annual precipitation at nearby Gateway averages 11.3 inches or 28.7 cm (source).  And aridity is only one of the challenges.  Prince’s plume is a reliable indicator that there's selenium in the soil.

Selenium in trace amounts is beneficial to plants, and dietary selenium is required by animals, but there’s a fine line between benefit and toxicity.  Plants containing selenium are toxic to most animals, and too much selenium reduces seed production in many plants.  Yet it doesn't bother the prince's plume. 

Stanleya pinnata (S. tomentosa at the time) from a study of seleniferous soils and toxic vegetation in Wyoming (Beath et al. 1946).

Prince’s plume doesn’t just tolerate selenium, it accumulates it – mainly in pollen, ovules, and leaf margins.  In fact, it’s a hyperaccumulator, containing 10 to 100 times as much selenium as other plants at the same site.  These levels are detrimental to most plants, but in prince's plume there appears to be no impact on pollinator visitation nor on reproductive output, perhaps due to the chemical form in which the element is stored (El Mehdawi & Pilon-Smits 2011).

Furthermore, prince's plume benefits from accumulating toxic amounts of selenium – it discourages both chomping herbivores and sucking pathogens.  For example prairie dogs eat prince's plume if selenium levels are low, but avoid plants with high concentrations (Freeman et al. 2009).  Presence of selenium has been shown to deter phloem-feeding aphids also (El Mehdawi & Pilon-Smit 2011).

Prince’s plume in Utah.  Courtesy USDI Bureau of Land Management.

This would seem a perfect plants-and-rocks story – a geobotanical tale of selenium and the prince’s plume.  Unfortunately we haven’t figured out the geological part.  Prince’s plume grows in western North America on seleniferous soils derived from fine-grained sedimentary rocks – shales, mudstones and siltstones (source).  Some geologists attribute this selenium to Mesozoic volcanic activity, but others disagree (reviewed in Rosenfeld and Beath 2013, pp 9-12).  Once again, more work needs to be done … the search continues.

Footnote:
1  The North American El Dorado was one of the mythological Seven Cities of Gold which lay somewhere north of Mexico (16th century).  UPDATE:  See Richard's Comment below for more information about this El Dorado and its location (about 250 miles south of where I found the prince's plume).


Sources (in addition to links in post)

Beath, OA.  1946.  Some rocks and soils of high selenium content.  Wyoming Geological Survey Bulletin No. 36.

Brown, TA and Shrift, A.  1982.  Selenium: toxicity and tolerance in higher plants.  Biological Reviews 7:59-84.

El Mehdawi, AF and Pilon-Smits, EAH.  2011.  Ecological aspects of plant selenium hyperaccumulation.  Plant Biology 14:1-10.

Freeman, JL et al.  2009.  Selenium protects the hyperaccumulator Stanleya pinnata against black-tailed prairie dog herbivory in native seleniferous habitats.  Am J Bot 96:1075-1085.

Rosenfeld, I and Beath, OA.  2013.  Selenium: geobotany, biochemistry, toxicity, and nutrition.  Academic Press.