This post is just a test to see if I can make and include a video of my tree for Lucy's Tree-following Project. It won't be up for long.
It worked! Hooray!! More cottonwood news soon.
Sunday, March 2, 2014
Much about Vedauwoo is mysterious, including its name. Vee-dah-vú is said to be an Indian word meaning earthborne spirit, but no one knows which tribe called it that, if any.
|Curious granite mushroom.|
Vedauwoo is inhabited by tors -- odd rock sculptures that defy understanding. In the early days of my blogging, I naively chose Vedauwoo tors as a topic. It took me quite a long time to put something together, and in fact I ended up with three posts: Creatures of Stone, Creatures of Stone II -- genesis, and Creatures of Stone III -- the rest of the story?
Here’s a quick summary of the best explanation currently: 1) granite fractured while cooling underground; 2) ground water moved through the fractures weathering the rock and widening the cracks; 3) the granite was exposed during and after uplift of the Laramie Mountains, when overlying sedimentary cover was removed; 4) weathering continues, with blocks periodically falling.
|Two-staged tor formation; click on image to view.|
The tors are made of Proterozoic Sherman granite. It was emplaced 1.4 billion years ago, but it’s not clear how nor why. It’s close to and appears to be associated with the Cheyenne Belt, a continental suture created when the Yavapi province, a collection of island arcs, collided with the Archean Wyoming Craton (below). The suture may have provided a zone of weakness for mantle-derived material (the granite) to be emplaced near the surface (Frost et al. 1999).
|Vedauwoo is just south of the Cheyenne Belt, where the Yavapi province was accreted to the Wyoming craton (map courtesy Written in Stone).|
Then there’s the mystery and intrigue of black-and-white photography -- I love it! But I’m still experimenting and learning what works. For black-and-white I like relatively simple compositions, such as patterns and collections of bold shapes, especially with strong contrast in light. Odd arrangements and perspectives also attract me. The tors of Vedauwoo are great in all these ways, but it takes thought, effort and especially trial-and-error to shoot them to good effect.
|strong contrast in light,|
|and odd arrangements -- all are common at Vedauwoo.|
There’s general agreement that one should think in black-and-white, shoot in color, and then convert to black-and-white in post-processing. That’s what I’ve done so far. My post-processing is simple, all in iPhoto. I reduce saturation (color) to zero, and often adjust light and shade with the histogram. Sometimes I increase definition. This works pretty well, but one of these days I’m going to try a high-contrast setting on my camera when I shoot in color for black-and-white.
|Quaking aspen against Sherman granite.|
|More aspen -- with leaves.|
|Small aspen and a tiny tor dance in the wind.|
|Where does this mysterious trail lead? east of the Moon? west of the Sun?|
For more on black-and-white photography, see Centennial in Black and White.
Frost, C.D. et al. 1999. Petrogenesis of the 1·43 Ga Sherman batholith, SE Wyoming, USA: a reduced, rapakivi-type anorogenic granite. J. Petrology 40:1771-1802.
Tuesday, February 25, 2014
So-called “fragile” prickly pear (Opuntia fragilis) takes revenge on an unsuspecting botanist.
Getting scotch thistle (Onopordum acanthium) into a plant press requires caution and the right tools: brick hammer to dig up plant, knife to slice heads into pieces. Click image for view of dangerous plant parts.
Plants have lots of vexing and painful parts -- spines, thorns, barbs, prickles, glochids, retrorse hairs and dangerously-sharp leaf tips. As biologists we assume these are adaptations, but for what? It’s tempting to think defense.
The leaf tips of Agave lechuguilla, shin dagger, can be deadly. From USDA Plants.
|Retrorse barbs of wild licorice (Glycyrrhiza lepidota) look nasty ...|
|... but they're only a few mm long, as seen here in context (dog fur).|
Puncturevine nutlets are especially devilish (Tribulus terrestris; source).
|Puncture vine mat and closeup of flower. Flowers are 0.5-1 cm across. Source.|
The most infamous pain-inflicting plants in North America are cacti, with their diverse assortment of spines. Surely they are adaptations to discourage animals from eating the delectable fleshy stems, so appealing in deserts. This is a reasonable conclusion.
Prickly pear cacti have tiny very sharp spines called glochids below the regular spines. They're especially difficult to remove from skin. Some cultivars are spine-free -- these are the tasty nopales or indian figs.
However there seem to be other “purposes” for cactus spines as well as defense. Consider that they’re found mainly in deserts -- plants of moister regions are rarely covered with spines. Might spines shade stems and reduce water loss? For the fragile prickly pear (beginning of post) and the infamous jumping cholla of Arizona (below), they appear to be "for" dispersal. Stem segments readily disarticulate, and can attach to an unsuspecting passerby thanks to the spines.
Though many purposes can be conjured up by a curious partially-informed mind, it’s difficult to know why a plant structure evolved -- what it’s an adaptation for. We rarely understand the evolutionary history of adaptive traits. For example, something may have evolved for an unknown purpose long ago, and later was co-opted or redesigned for something else. The opportunities for speculation are infinite. There’s a thought-provoking discussion about this dilemma at The Mermaid’s Tale: Why do cholla cacti use torture?, written by Anne Buchanan after a hike in the Arizona desert.
“The problem is that there may be no single reason, nor even any single kind of history involved here. ... we think this illustrates why, even when the assumption that the trait is 'adaptive'--that is, is here ultimately because of natural selection--that assumption is hard to prove and in particular the reason is hard to be sure about.”[Warning: the included video featuring an unfortunate victim of cholla torture is not for the squeamish.]
Jumping cholla, Cylindropuntia fulgida. Source.
Obviously we need to be cautious, not just in walking through dangerous plants but also in thinking about them. Like so many biological phenomena, the more we learn, the more complicated it gets [sigh] but of course that makes the stories even more wonderful! Here’s a great example:
Bullhorn acacia, Acacia hindsii.
The bullhorn acacia is a well-armed desert tree, with long spines that deter browsers in ways both obvious and surprising. Obviously the sharp-tipped spines discourage larger animals, but they don’t do much against insect pests and fungal pathogens. Fortunately they also serve as ant homes, and in fact, the acacias strive to make the neighborhood attractive to ants by providing nutritious food via extrafloral nectaries. It’s worth the investment. The ants sting anything that tries to eat the leaves, from caterpillars to cattle. Furthermore, acacias with healthy populations of the right kind of ant have a reliable supply of antibiotics to fight fungal infections on their leaves. Their drugs are produced by bacteria living on the ants’ legs. What a nice arrangement! For more, see The Economist, Protect and Survive; and Science Daily, Ants protect acacia plants.
This post is my submission to this month’s Berry Go Round, a blog carnival for plant lovers. It’s hosted by Garry Rogers, and the topic is Botanical Warfare.
Spines are for beauty too -- for those who look close (from Excruciatingly Beautiful).
Saturday, February 22, 2014
|Cattails on right, dogtail on left.|
Here in Laramie we are a resolute people, as Garrison Keillor might say. We know there are many advantages to living here (but we don’t tell what they are as we want our town to remain small and friendly). We know they far outweigh the disadvantages, which we stoically endure. But there are days. There are days for example when it's dangerous to get out of the car if it's parked into the wind. My parking spot at home points west, and yesterday it was all I could do to open the car door and get my groceries out and not be crushed as it slammed shut. The average wind speed at that time was 45 mph.
So you can imagine my joy when I awoke this morning at a normal hour, instead of at 3 am due to the roar of wind (wind roars when its steady speed is greater than about 35 mph). You can understand why I did not mind that the day was gray with a light snow falling, and can sympathize with my decision to forego laundry for a photo excursion. But of course I’m making assumptions. If you’re a person who disapproves of impetuous behavior, then read no further.
I abandoned the laundry and went for a walk. I kept my camera on the entire time and photographed whatever I found, for it all seemed beautiful to me.
|The sun shone dimly through thin clouds and light snow.|
|Tumbleweed hanging out with railroad tie (prickly Russian thistle, Salsola tragus).|
... and reached the Laramie River.
|This is the tree I'm following, a cottonwood.|
|Another tumbleweed taking the day off, resting on river ice (kochiaweed, Kochia scoparia).|
|Cattail still-life (Typha latifolia).|
|This one is waiting for the wind to return, so it can send more offspring out into the world.|
|Just west of the wetland is Interstate 80, one of the main arteries of the USA. Crossing the Laramie Basin isn't so bad, but the mountain passes on either side can be terrifying in winter. But we need our stuff!|
|Rich's bench ...|
|... and Rich's Four Noble Truths (click on image for a better view).|
Saturday, February 15, 2014
Stirred by Lucy’s enthusiasm, I took my camera with me on my morning walk along the Laramie River. It’s still winter here, so I got side-tracked by the beauty of river ice.
Center foreground -- our tracks from last week, now inverted because most of the snow has blown away.
Footbridge across the river, once a railroad bridge.
Shadow patterns cast by grass, brush and trees.
My field companion, as faithful to me as his shadow is to him.
I returned to my mission and soon chose a tree for 2014 (below left). Or maybe I should say “trees” as there are multiple trunks. Most of the trees along the river grow this way, in clumps. Is this a single individual, connected underground?
Winter landscapes can seem so dreary. But if we can get out of that black-and-white mode caused by snow, we realize there's quite a bit of color after all.
|Another view -- the tree stands over its cousins, the willows.|
|Its twigs appear bare at first glance. A closer look (click on image) reveals buds ready for spring.|
Rocky Mountain Tree Finder, partly because I love dichotomous keys and this one is so easy to use. How does it work? At each step I pick one of two choices, thereby eliminating a substantial number of tree species from consideration. I continue this way until the only one left is the one I’m standing under! It seems like magic, even after all these years.
In this case, the path to identification required 14 steps, including the following:
1) Leaves needle or scale-like OR ordinary? ordinary
2) Leaves compound, composed of several leaflets OR simple? simple
3) Leaves paired on opposite sides of twigs OR not? not (no leaves, so checked leaf scars)
4) Leaves lobed OR not? not
5) Leaf stalks (petioles) longer than 1 inch OR less than? less than
... etc. ...
10) Leaf margin with big & little teeth OR single-sized teeth? single-sized
|Leaf margin with single-sized teeth.|
14) Leaf tips often blunt rather than sharply pointed OR not? often blunt rather than sharply pointed (see illustrations below)It appears to be the narrowleaf cottonwood, Populus angustifolia (click on image for more information).
I also attempted to identify the tree with the Winter Tree Finder. This is challenging because the useful characters are harder to see and not as familiar. I had to look at terminal buds, leaf scars and vein scars -- so let’s digress.
|From the Winter Tree Finder.|
The terminal bud is where the twig will start the year's growth. Leaf scars are left when leaves fall off. They contain vein scars -- remnants of conduits (phloem, xylem) for transporting water, nutrients, carbohydrates and more.
Now back to identification. I went straight to the cottonwood section. The Winter Tree Finder says terminal buds of cottonwoods are symmetrical. According to the Audubon Society's Field Guide to North American Trees, Western Region, terminal buds of the narrowleaf cottonwood are resinous and smell of balsam. Let’s look:
The terminal bud is indeed symmetrical, and somewhat resinous too. I didn't detect a balsam odor.
The Winter Tree Finder says leaf scars of cottonwoods are crescent-shaped with three vein scars. Sure enough, there are three vein scars on each crescent-shaped leaf scar:
The leaf scar below the bud is from last year; the one near the base of the twig is probably two years old.
The terminal buds, leaf scars, and vein scars of my tree all match those of cottonwoods. But I couldn’t go any further in the Winter Tree Finder because it covers the eastern USA, and Wyoming is in the west.
I'm sure this is a cottonwood and probably a narrowleaf cottonwood. The bark looks right: “smooth, becoming gray-brown and furrowed into flat ridges at the base” (Audubon Society Field Guide to North American Trees, Western Region). It's growing in the right kind of habitat -- lowlands or near water -- and well within its range (see previous map).
I will check my tentative identification after the tree leafs out, but first it will bloom and I'll need to investigate that as well. Cottonwoods have unisexual flowers, either male or female, and the sexes are on separate trees (dioecious). Thus I’ll learn whether this clump is male or female -- or maybe both, suggesting these are separate trees after all.
However I shouldn't dwell on tree activity right now. It's only February. Cottonwood flowers and leaves won't appear for months yet, probably in May, at least that's what I think I remember. I don't always notice -- but this year I will.