AW#47 -- Field Notes

This month’s Accretionary Wedge is being hosted by Jennifer at Fuzzy Science, and the topic is Field Notes.  Now that’s a broad one! ... I’ve been waiting to see what came to mind.  It finally appeared just in time for the deadline today, June 31.  These are botany field notes, perhaps at first glance not appropriate for the geoblogosphere, but they are notes about a plant that grows in rock ... and not just any rock.  And like all field books, when we peruse them we can visit the past, and sometimes even meet the early explorers and share in their discoveries.

The page above is from an early field book of Aven Nelson, Founding Father of Wyoming Botany.  The University of Wyoming Library currently is scanning all his field books, and soon they will be available online.

Nelson was hired by the University in 1887 as Professor of English.  It was only after all six of the faculty had arrived at the new university that the president discovered he had inadvertently hired two English professors.  Nelson had attended six botany lectures as an education student, and so was made Professor of Biology.  He went on to make many pioneering contributions in botany in Wyoming and the Rocky Mountains, and was an inspirational teacher, with many of his students becoming prominent botanists themselves.

Nelson's collecting areas in 1894 and 1895 (click to view).

Laramie columbine;
by Isobel Nichols.

In 1895, Nelson was in the midst of a “systematic survey” of the Wyoming flora, devoting his summers to expeditions by horseback across the state.  On August 4, he was hiking up a canyon in the rugged Laramie Mountains of southeast Wyoming when he discovered a small columbine growing in granite on the east side of Laramie Peak.  In his final report the next year, he described Aquilegia laramiensis, the Laramie columbine, one of the earliest of his many botanical discoveries.






[Fast-forward ca 110 years ...]

Field botanists collect a lot more information now than in the good-old-days (click to view), but of course we don't have to travel by horseback and care for our trusty steeds (until they break down).

In 2003, the Laramie columbine still was known from only a few locations, all in the Laramie Mountains, most on lands managed by the Forest Service and Bureau of Land Management.  Off and on over the next six years, we worked for these agencies to inventory and prepare a status report on the apparently-rare Laramie columbine.  It was a tough job, but the scenery was fantastic, and I was awestruck whenever I found elegant little columbines growing in nooks and crannies of rugged granite outcrops.

In keeping with its name, the Laramie columbine grows only in the Laramie Mountains of southeast Wyoming.  It remains a rare plant even after extensive survey, though it is fairly common within its rugged and tough-to-access habitat.  It grows mainly in Archean granite outcrops, but also in metamorphic rocks from early Proterozoic accretionary events. The columbines are restricted to well-shaded sparsely-vegetated microsites, and looking for them is a bit like hunting for easter-eggs ... chocolate easter-eggs that is, i.e. well worth the effort!

I had a personal reason to be excited about this project, for I had "met" Aven Nelson during my first encounter with Wyoming botany.  As a budding botanist and seasonal ranger at Devils Tower National Monument many years ago, I was curating the herbarium and came across plant specimens collected by George W. Giles in a project for the Work Projects Administration (WPA) in the early 1930s.  In his field notes, I could feel and empathize with the enthusiasm of a young botanist.  I read correspondence regarding the specimens he had prepared and sent to Professor Aven Nelson at the University of Wyoming, the leading expert on the region's flora.  And now here I was, following in the great professor's footsteps in the rugged Laramie Mountains.

Aven Nelson in the field, from UW archives.

For more on Aven Nelson, the Laramie columbine and the northern Laramie Mountains, see Plants and Rocks: columbines and granite.

tafoni #2

Continuing my series, we go a short distance west from Grand Junction, Colorado, to view tafoni in Rabbit Valley.

Remnant features can be tough to explain -- they are products of weathering and erosion, created and defined largely by what has been taken away.  Often we can only speculate as to what happened but here in Rabbit Valley, it appears someone has it figured out.

The origins of tafoni -- natural pockets in rock -- often are mysterious, but not here.

Nested tafoni -- smaller pits inside the large cavity above.

The explanation on the sign seems reasonable, as the rock here is a mix of fragment sizes and types.  It is gravelly sandstone from the Late Jurassic Morrison Formation, deposited by rivers roughly 150 million years ago.  Think about wading a river and walking across sand bars and gravel bars.  Here we have sand and gravel bars that dinosaurs walked across, now preserved in rock.

Gravel bars of the past ... tafoni of the future?

Rabbit Valley, home of the Mygatt-Moore dinosaur quarry, is accessible from Exit 2 on Interstate 70, about 25 miles west of Grand Junction. A 1.5-mile nature trail tours Morrison boulders and outcrops just east of the quarry.

"Trail through Time"

Fossilized dinosaur pelvis in gravelly sandstone.

150-million-year-old sand and gravel deposits, now rock.

Left:  Boulders on the dry slopes of modern-day Rabbit Valley were once beds of sand and gravel in rivers where dinosaurs drank. Below: Rabbit Valley back in the day.

Where dinosaurs drank -- for the full story, see Ty Templeton’s Bun Toons.

Recommended reading -- Weeds

“Beware the triffids ... they grow ... know ... walk ... talk ...stalk ... and KILL!”
Movie poster for The Day of the Triffids, 1963.

Weeds have a bad reputation.  They invade gardens, croplands and wildlands, and we dig, pull and spray in response, often at great expense.  They can inspire a fear almost as great as the terror of the triffids -- those genetically-modified plants (in 1963!) that stalked, stung and killed people, and then ate them.  Last week I found the dreaded field bindweed in my garden.  I dug deep in pursuit of its insidious root system, and burned the whole lot in the wood stove.

Field bindweed aka creeping jenny, Convolvulus arvensis.  Photo by Bouba.

Is this level of anxiety justified?  Not always.  Weeds are wrapped up in a tangle of definitions, values and judgements that change with time and human taste.  Richard Mabey provides an interesting and entertaining account of it all in Weeds: in Defense of Nature’s Most Unloved Plants (2010).

Weeds often are defined simply as undesirable plants, but “undesirable” is a matter of context.  Furthermore, in some contexts the marvelous adaptations of weeds can benefit humans -- their prolific offspring, able to travel far and wide, means that something will be growing almost everywhere.

Left: ivy-leaved toadflax, Cymbalaria muralis, has colonized a wall. Its nicknames speak to the ability of weeds to spread far and wide -- traveling-sailor, mother-of-thousands.  By SP-KP.

Below:  vervain (Verbena bracteata, left) and knotweed (Polygonum sp.) take advantage of open habitat in asphalt.  The vervain's leaves are about 5mm across.

Knotweed, tumbleweed and kochia weed, bane of my garden, grow in profusion just upwind of our neighborhood where the State recently “improved” the grounds around the Territorial Prison.  We would miss them if they weren't there.  Like many weeds, they colonize disturbed sites, hold the soil in place, and keep it from turning to dust in the wind.  For this I am grateful though I regularly chase tumbleweeds from my yard.

As Mabey repeatedly points out, a weed to one person or in one place or at one time can be a treasure in a different setting.  His examples are fascinating.  Most memorable are the trench gardens of World War I.  Soldiers used scraps of battle debris to fence small plots where they transplanted weeds from nearby fields.  And of course there were the poppies:

“Red poppies, and a blue flower, great masses of them, stretched for miles and miles.  The sky was a pure dark blue, and the whole air, up to a height of about forty feet, thick with white butterflies.  It was like an enchanted land; but in the place of faeries, there were thousands of little white crosses ...” William Orpen, An Onlooker in France 1917-1919

“We are the dead.  Short days ago we lived, felt dawn, saw sunset glow ...”
From In Flanders Fields by John McCrae.  Photo source unknown.

Archeological evidence and paleoenvironmental reconstruction show that plants always have moved around in response to change, and Mabey includes detailed accounts of specific comings and goings of weedy plants.  Might these traveling plants play a helpful role in the face of climate change?  Today’s newcomers, though unwanted at present, may be the first arrivals of vegetation that will support us in a warmer world.

Weeds are not a simple issue, as the author makes clear. While some are obvious threats, others should be addressed with reason rather than reaction.  Is it reasonable to douse them with broadcast herbicides year after year, especially when we're making little or no progress in the battle?

This book focuses on Britain and Europe, with less coverage of weeds elsewhere.  Mabey acknowledges the wide variation in weed danger across the world.  It is much worse on isolated land masses such as Australia and Hawaii, whereas other ecosystems, such as his own, appear to be more resilient or resistant to invasion.

Also reflective of the author's background is the abundant British English, which made me scratch my head at times but never enough to detract from the wonderful reading.  And my vocabulary has expanded ... now I know a verge when I see one!

verge |vərj| noun

Brit. a grass edging such as that by the side of a road or path.

(Oxford American Dictionaries)

Dandelion, sow thistle, evening primrose, yellow sweet clover and kochia weed
spread out from the verge, intent on taking back the streets.

tafoni #1

What are all those holes?!  That's tafoni, in Entrada sandstone in western Colorado.

Too much work right now -- three field seasons’ worth of information to describe and discuss in a report due in a few weeks.  A recurring sense of déjà vu finally focused on a time in the distant past.  This is the same scale of suffering I experienced while writing my thesis!  So for now, I’m falling back on a stash of tafoni photos in lieu of written posts.

Tafoni, natural pockets in rock, range in size from little pits to huge cavities and come in an entertaining variety of shapes and patterns.

Elongate tafoni; 52-lb dog for scale.

Sometimes there are tafoni within tafoni.

Above, nested tafoni ... not to be confused with nest in tafoni, below.

Tafoni form through weathering (decay) and erosion (transport away), though specific processes remain mysterious in many cases.  This is another one of those wonderful geo-situations where educated speculation can run wild.

An observation -- tafoni are lined up parallel to bedding planes -- leads to an idea.  Perhaps there was an interval of deposition that included coarser fragments, which fell out when exposed by erosion, opening tiny cavities that weathered with time.

Alas, around the corner there are diagonal patterns as well.

Whatever their origins, tafoni patterns are beautiful, fascinating, even mesmerizing, and for awhile I was completely lost in photographing them.  Not a bad way to spend a morning.

Sparky, ever the pragmatic dog, focused on utility instead.

I think I see something very interesting.

Yep, let's go check it out.

Black dog finds welcome respite from heat ... in tafoni.

All photos are from the McInnis Canyons National Conservation Area south of Grand Junction, Colorado, where there is a nice network of trails touring the steep fold (monocline) on the north flank of the Uncompahgre Plateau.  Tafoni are common along the Devil's Canyon Trail in Jurassic sandstone, deposited “in an eolian setting that was on the northeast margin of a large dune area, or erg, that occupied most of the Four Corners area" (Scott et al. 2001.  Geologic Map of Colorado National Monument and Adjacent Areas, Mesa County, Colorado; see the actual map here).

There is an entire website devoted to tafoni and its puzzling origins -- Jon Boxerman's TAFONI.

Calling all plant geeks

In the Company of Plants and Rocks is hosting June's blog carnival at Berry Go Round, featuring all things botanical.  This is a challenge to geobloggers as well.  The deadline is approaching so get your creative juices going.  Plants, pests, pathology, seeds, weeds, wildflowers, food, fuel, fossils, science, art, music ... the possibilities are endless.

This morning was our first calm one in a week, completely still with nothing to disturb the white decor (aka litter, trash) that had blown in yesterday and now festoons the vegetation along the tracks.  Or is that trash?

No! All those pieces of white plastic actually are evening primroses, still open this morning.

Nuttall's evening primrose, Oenothera nuttalli; flowers ca 2 inches across, with buds above.

4 sepals, 4 petals, 8 stamens and a 4-parted stigma -- must be Onagraceae, the evening primrose family.