Last Days in the Desert

Here is the (largely pictorial) summation of my last wanderings in the desert; please forgive my extreme procrastination.

 

Mexican Campion, Silene laciniata.  You can see a closely related
N.C. species (Silene virginica) in my July 2011 post about the Southern Appalachians.

Forefront: Century Plant,
Agave havardiana

 In mid-October Ben, Alex and I headed up out of the flat lands into the Chisos Mountains of Texas, the southernmost mountain range in the United States. Rising to over 7,500 feet, these mountains provide a a cooler, wetter, and generally more forgiving habitat in the middle of Big Bend National Park. Here you can find actual trees, including big-toothed maple, Ponderosa Pine, Douglas fir and Arizona cypress.

When we parked our truck in the Basin and began lacing up our boots, we got our first glimpse of the hike in. Though the green slopes called seductively with their promise of conifers and cooler temperatures, we knew that a 5 mile, nearly thousand meter elevation gain hike with 55 pound packs stood between us and our abode for the next three days, Boot Cabin. We trekked on.

Boot Cabin was a welcome sight, indeed. Not content to rest our legs for too long, however, we hiked further up Boot Canyon to do some spring scouting and take in the vista from the South Rim, which we had been told was the best view in the whole park.

The mountain shadows creep eastward, Abbey's "whiskey-colored light" fading slowly to pastels on the horizon, and the desert falls into dusk.

We sat down for a spell, while the swifts flew like bullets overhead, their aerial maneuvers almost too fast to see.  Green arteries flowed from the Chisos into the parched land below and from our giant's perch it seemed the ancient formations were but small piles of sand. As we marveled at the expanse before us, a lone Monarch butterfly made its way over the edge of the Rim and floated lazily south toward Mexico and a warm winter.

This Monarch Butterfly (Danaus plexippus) is headed south out of Big Bend, and can cover over 80 miles in a single day. The Monarch is known for its long yearly migration, over 1,000 miles from northern U.S. or Canada to Central Mexico for the winter. Most Monarchs live only 4 or 5 weeks, but as autumn approaches in the butterfly's northern home, a special generation is born which lives 7 to 8 months! These long-lived individuals make the southerly migration, winter over, then head back north. But these old timers don't make the full round trip -- several breeding rounds along the way split up the return journey amongst multiple generations.

Boot Cabin is maintained as a backcountry research cabin by the park. Outfitted with solar-powered lights and refrigerator, bunk beds and a fully equipped kitchen, we decided by the end of the trip that we could all make Boot Cabin our permanent home. (The damaged exterior in the picture at left? That's from bears trying to get inside.)

Alex strolling through a Chisos "prairie."

A mule deer spotted on the way to Cattail Spring.

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In late October Alex and I headed to the Gila Wilderness in southwest New Mexico for a few days out of the desert. Hiking below golden, stretching aspens and seeing our breath in the mornings, it was hard to believe we hadn't even traveled over the state line. Our route, the Redstone-Baldy Loop, took us from low country along Whitewater Creek, all the way up to the highest peak in the Wilderness, Whitewater Baldy (10,895 ft.).

 It was as if someone had tipped a bucket of gold down the mountain.

Whitewater Baldy really isn't that bald, we discovered. Above is the view from the peak. I found that to really get the appropriate vista, you had to climb 30 feet up in a spruce tree...

 That's better.

 A Wild Geranium on the trail down to Whitewater Creek.

 Aspen trees (Populus tremuloides) are clonal organisms, propagating primarily through root sprouts rather than sexual reproduction. This leads to massive clonal colonies that are in fact a single organism, with the oldest known aspen colony currently celebrating its 80 thousandth (or so) birthday! That's right, the Pando Colony in Utah is both the oldest and heaviest known organism on Earth: over 6,000 tons and more than 80,000 years old.

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Our second to last tour took us to Elephant Tusk, a remote section of Big Bend hosting a (supposed) menagerie of springs. Briskly flowing brooks were indeed a welcome prospect, but what was even more exciting for me was that we were mule packing! This time honored tradition is still alive and well in Big Bend, which employs its own full-time "mule skinner" (Joseph, seen above). The whole process -- from loading the mules on the trailer, to wrapping all our gear in large canvas tarps to hoist onto the mules' backs, to watching these hardworking beasts trot speedily ahead of us on the hike in -- was nothing short of fascinating. Able to carry 300 pounds apiece, the line of mules above carried 4 days worth of gear for 6 people a distance of 10 kilometers in about 2 hours.

Ocotillo (Fouquieria splendens) is another well-adapted desert plant very common in the Chihuahuan Desert. Most of its life is spent as a rather dead looking, spiny, leafless stalk (left) that can reach heights of 30 feet (more commonly 10-15 ft). But look closely and you'll see green stripes along the stalk -- these are active photosynthetic areas, allowing the plant to continue to produce sugars while leafless. Leaves (center) are produced quickly in response to rain, and are kept until drought conditions return, when these water-costly structures are dropped and the plant returns to its spiny, barren state. Brilliant orange-red tubular flowers (right) are produced at the tips of the stems sporadically throughout the year, with pollination services provided by hummingbirds and honeybees.

Big Bend Acanthus (Anisacanthus linearis), with its gracefully recurved petals,
is endemic to the Chihuahuan Desert.

I have no idea what caterpillar this is, but it sure is striking.

 Elephant Tusk (mountain on right) at sunset.

Finally, a Tarantula! I'd been waiting all fall to spot one of these beauties;
this one was relaxing on the rushes at my very last spring.

Resurrection Plant (Selaginella lepidophylla), is a Chihuahuan Desert native with an amazing tolerance for dry conditions. When water is scarce, this spikemoss curls up (as above) and enters a state of dormancy, tolerating moisture contents as low as 6% (most plants cannot handle below 75%). When it rains, Selaginella's cells rehydrate and its stems unfold in a flush of green (below). 
 

I hope you have enjoyed exploring the arid Southwest with me. The organisms inhabiting this harsh landscape exhibit some of the most remarkable adaptations seen in nature, and their environmental tolerances are a model for our own personal ones. If you'd like to read more about desert ecology, I highly recommend Desert Ecology by John B. Sowell.

I'm now working in the Plant Ecology Lab at Archbold Biological Station in Florida, so my next post will be from the Lake Wales Ridge.

Until then,

john

Rattlesnakes and Jewel Bugs

Blackfoot Daisy (Melampodium leucantham)

The Silver Creek area of Sevilleta National Wildlife Refuge

So, what makes a desert? Lack of water, right? But why exactly do deserts lack water? There are a few possible explanations. Firstly, the simple fact of being far from the ocean, which is where most of the world’s atmospheric moisture originates, can cause aridity. As humid air moves inland, precipitation occurs, and the further inland that air goes, and the more precipitation events that stem from it, the less available moisture there is for those inland, landlocked areas.

Apache Plume (Fallugia paradoxa), with its feathery styles swaying like lavender tinsel in the breeze

Another cause of desertification (which can result in deserts actually being on the coast, right next to the ocean) can be the presence of cold water just offshore. This is explained by the phenomena of condensation and evaporation, and can be attributed simplistically to the notion that warm air can hold more moisture than cold air (holding isn’t actually the correct way to describe this, though it is commonly stated as such; it really has to do with temperature affecting the speed of the water molecules and influencing their tendency toward a gaseous or liquid state; see http://www.usatoday.com/weather/tg/wevapcon/wevapcon.htm ). Water evaporates in the middle of the ocean, raising the moisture content of the air above it. As this humid, warm air moves toward land, it passes over the relatively cold coastal seas, where much of it condenses as rain or fog. By the time this air mass makes land, it has lost much of its original moisture, and as it warms over land and its relative humidity decreases even further (because warm air “holds” more water), the chance of precipitation is slim, and voila, you’ve got an arid coastline.

The Sierra Ponce cliffs rising 1,500 feet above the Rio Grande in Big Bend National Park

 Another “desert cause” involving condensation is the rain shadow effect, which you’ve probably heard of (of course, you could have very well heard of, and understood better than I, all of these mechanisms I’ve so long-windedly described to you). As warm, humid air moves inland from the ocean, it hits a mountain range, forcing it to rise, cool, and ultimately dispend much of its moisture as precipitation along the range’s sea-side slopes. Once our air mass clears the peaks and begins to descend, it warms, lowering its relative humidity (as in the previous example) and making for little chance of rain in the forecast for whatever unfortunate souls reside inland. It is this mechanism which causes the aridity of the Chihuahuan Desert, which is sandwiched between the Sierra Madre Oriental range to the east (blocking air from the Gulf of Mexico) and the Sierra Madre Occidental range to the west (blocking air from the Pacific).

Evapotranspiration rates are also very important in determining desert aridity, but I won’t go into that. No, really, please, you don’t have to thank me. Basically, it gauges the water lost from a landscape based on a combination of surface evaporation and plant transpiration. As you could probably guess, these rates are VERY HIGH IN DESERTS.

In mid-September we traveled to the Sevilleta National Wildlife Refuge, about three hours north of Las Cruces, where we were put up in very posh, new research housing. Compared to our usual accommodations of rocky desert ground, with lechuguilla, prickly pear and dog cholla threatening impalement on all sides, this was a real treat, indeed! (To be completely honest, I do sleep better outside, but having a kitchen and shower was extremely convenient.)

Greeting us when we first arrived at Sevilleta, this Blister Beetle (Genus Cysteodemus) is a true desert jewel

The Juniper grasslands of Sevilleta underneath the dramatic cover of a building thunderstorm

One Sevilleta spring emerged in this spectacular limestone canyon

The Refuge system was started by Theodore Roosevelt in 1903 and is tasked with protecting the nation’s fish, wildlife and plants. As told to me by a Refuge employee: whereas the National Parks system is, “people and recreation first, natural resources second,” a Refuge’s mission is, “natural resources first, people second.” Of course, with the ever needling fingers of politics and bureaucracy this goal is not always realized, but the principle of the idea is a good one and, I like to believe, often realized. Many Refuges are open to limited recreation such as hiking, hunting and fishing, but Sevilleta is maintained mainly as a research and conservation reserve, with little public access. Thus, it was especially exciting to visit!

Bordered Plant Bug nymphs (Largus sp.) feeding on Horsetail Milkweed (Asclepias subverticillata)

A Giant Whipscorpion (Mastigoproctus giganteus), about 7 inches in length and incredibly creepy

While scoping out a spring at Sevilleta, I crouched down to pass under a dead tree limb and almost stepped on the rattle of my first rattlesnake! 

I froze (well, I did have to get a picture...), he (she?) turned to look at me for what seemed like about 60 seconds but was probably 5, and then slithered under an evergreen sumac. Later I identified it as a Mojave Rattlesnake (Crotalus scutulatus), which has the distinction of being one the most venomous snakes in the New World. While most rattlesnakes carry a hemotoxic (tissue-destroying) venom, one variety of Mojave possesses a strong neurotoxic venom that can cause severe paralysis and nervous system damage. I'm not sure if this individual happened to be of that variety, and I'm glad I didn't find out. I carefully sidestepped the sumac bush and continued along the brook, and promptly came across my second rattlesnake 10 feet downstream! 

This one was completely unperturbed by our sampling and did not move a centimeter for the entire duration of our workday.

The next tour took me once again to Big Bend National Park, where I got my first taste of the Chisos Mountains.

Sun rising over the Chisos

Scarlet Bouvardia (Bouvardia ternifolia) paints brilliant splashes of red along the paths of the Chisos, and is a hummingbird favorite

Trans-Pecos Spiderwort (Tradescantia brevifolia). I did not place the feather there.

A Christmas Tree cholla (Cylindropuntia sp.) in bloom

Cacti such as the cholla above possess a unique metabolic pathway called Crassulacean acid metabolism (CAM) that is specially adapted for arid climates. Here's how it works: plants have small openings / pores in their leaves called stomata (singular: stoma), which they open and close as needed to assimilate and release gases like carbon dioxide. However, when a plant opens its stomata to suck in some CO2, it loses water through transpiration. This is, of course, a problem in the desert, but CAM plants have a workaround. When water is scarce, they open their stomata only at night, when transpiration rates are much lower. But obviously, this means that no sunlight is available for photosynthesis. So what CAM plants do is to take the assimilated carbon dioxide and combine it with an enzyme called PEP carboxylase, forming malic acid. These four-carbon molecules are then stored in the plant's vacuoles (plant storage closets), which in succulent plants like cacti are especially large and able to dilute the potentially damaging accumulation of acids. The next day, with the stomata safely closed, the plant "disassembles" the four-carbon molecules back into their constituent parts and uses the resulting carbon dioxide to proceed with photosynthesis. 

Chocolate Scented Daisy (Berlandiera lyrata)

A Metallic Borer Beetle (Acmaeodera sp.). The "Jewel Beetles" of this family (Buprestidae) have been used historically in jewelry making and Victorian art. Thanks to the folks over at whatsthatbug.com for their help in identifying the insect species in this post.

Creosote Bush (Larrea tridentata) is a characteristic shurb of the Chihuahuan Desert and one of its most remarkably well-adapted species. Most plants cannot survive dehydration to less than 75 percent water content; Larrea can go below 50 percent. Like many other desert species, it has very small leaves that allow the plant to stay cooler (due to a smaller boundary layer) and reduce transpiration rates. The leaves are also covered with a waxy cuticle that protects against water loss, and are partially drought-deciduous, meaning that as summer approaches Larrea can drop some of its leaves if water resources are too scarce (less total leaf area = less water loss) . As you can see in the pictures above and below, it covers large expanses of desert, with the individual plants spaced apart so evenly it almost looks like they were planted. There are a few theories to explain this, one being that Larrea's incredible efficiency in water uptake simply prevents other seeds from germinating in the soil around it. The regular spacing could also be caused by allelopathy, or the plant's ability to restrict the growth of other organisms in the micro-environment immediately surrounding it through chemical means.

Next post will be mountainous -- up in the Chisos of Big Bend and the Mogollon Mountains of the Gila Wilderness.

cheers,

john

A Rich Sparseness

“Water, water, water…There is no shortage of water in the desert but exactly the right amount, a perfect ratio of water to rock, of water to sand, insuring that wide, free, open, generous spacing among plants and animals, homes and towns and cities, which makes the arid West so different from any other part of the nation. There is no lack of water here, unless you try to establish a city where no city should be.”

- Edward Abbey, Desert Solitaire

Going to the desert to study water might at first glance seem strange, but where else would this study be of more use? The springs strewn so sporadically across the “wasteland” of the Southwest are literal oases, hotspots of biodiversity in the desert landscape and home to many rare, endemic species. And as the dense human populations of the arid states grow ever denser, causing the water tables to drop lower and lower, the fate of these life-sustaining water sources is increasingly uncertain.

I made my way out to Las Cruces, NM in August to begin work for the Chihuahuan Desert Inventory and Monitoring program, a National Park Service Directive. The I&M program tracks the state of natural resources within the park system, initiated by an Inventory of these resources, and followed with regular Monitoring surveys continuing indefinitely. 

Hiking to a spring in Big Bend National Park.
Note the bright patch of green above the crew's heads. That's the spring.
(There's a smaller spring to the right.)

A variety of floral, faunal, climatic and geologic I&M surveys have been instituted, but ours is concerned with water sources (springs, wells, seeps, etc.) found in the Chihuahuan Desert. Still in the initial inventory phase, we are preparing a database of information to guide future monitoring programs by collecting vegetation, aquatic macroinvertebrate and general habitat data.

For the purposes of the program, the Park Service has divided the park system into 32 ecoregional networks (see map above). The Chihuahuan Desert Network is composed of seven parks, including Carlsbad Caverns, Guadalupe Mountains, and Big Bend National Parks. (The network has also been contracted by the U.S. Fish and Wildlife Service to conduct sampling in some National Wildlife Refuges in the Southwest, so we get to go to those, too!)

Not all of the springs are remote -- one of our springs in the San Andres NWR used to be quite the popular picnic area back in the '40s and '50s. A big draw was surely the spring-fed swimming pool shown above, which was built by the CCC. 

The Chihuahuan Desert

The most biologically diverse desert in the Western Hemisphere and the largest in North America, the Chihuahuan Desert ecoregion is over 270,000 square miles and straddles the border between the United States and Mexico, reaching from just south of Albuquerque to just north of Mexico City. The multitude of habitats occurring within its extent – high elevation oak-pinyon-juniper woodlands, mid-elevation grasslands, low desert scrub, the gypsum dunes of White Sands National Monument— contributes to its startling diversity and makes it a veritable playground for the wandering amateur botanist.

A Fishhook Cactus erupting into spectacular bloom

Considered a “high desert,” much of the Chihuahuan lies above 4,000 feet, though it ranges from 1,000-10,000 feet across the whole expanse of the region. This high elevation (relative to other deserts like the Sonoran) means that winter temperatures drop below freezing fairly often, but trust me, the summers are still HOT, especially at low elevations. In fact, many of the springs we’re sampling now were not done during the past field season (spring and summer) because temperatures in Big Bend were simply too high to send crews out in.

Our camp at Big Bend was near the white house in the center of the frame. Note the large green patch on the right. Yep, that's a spring. They're quite easy to spot in the desert, if they're not dry (which many of them are).

My first few days of real work were in the beautiful San Andres National Wildlife Refuge. Due to the Refuge's location adjacent to the White Sands Missile Range (which houses, among other top-secret sorts of things, a NASA Test Facility), we had to be escorted to our sites and one day even acquired security clearance badges. (I'm pretty sure some of those jack rabbits were robots, too.) But any hassle was quickly forgotten once I got to my first desert spring. After a long, incredibly bumpy ride amid miles of desert scrub, a short hike brought us to a small brook where Flame Skimmers darted playfully among us, and cattails stood a stoic guard on their swampy feet. 

Flame Skimmer (Libellula saturata)

Golden Spur Columbine (Aquilegia chrysantha)

Once us newcomers got familiar with the protocol, and had learned enough of these new plants to get by, it was off to the Guadalupe Mountains to finish up training week. You might not think that the desert could offer that much of a botanical challenge, but I was learning new plants (and still am) at a rate that only heat, spines and job security could dictate.

Skyrocket, Scarlet Gila (Ipomopsis aggregata)
in the Gila Wilderness

I don't get creeped out by too many insects, but this centipede, at about 7 inches long, made me look around extra carefully before I sat down to eat lunch that day. It's a Scolopendra,
I think the species is polymorpha

This job has taken me to places few ever visit (or are even allowed to, in the case of the Wildlife Refuges), and has really given me a sense of the importance of these springs in a desert ecosystem. And aside from their integral ecological role, many of them are incredibly beautiful.

Wandering in the heat
One pace only gets you so far
And nowhere, really

Ashes of the mountains
His discarded progeny
Litter the ground and make violent attempts
To enter eye and mouth

A break in the monotone frame
A flash of green, too verdant to comprehend
And the ground grows softer
The spines sparser
The trickle of life sounding so sweetly on the ear
Amazed to see a shadow longer than your own

Sarcostemma sp., a twining member of the Milkweed family

My first real tour was in Big Bend National Park, in Texas. There is really no other adjective that could rightly be a part of that name. It is, first of all, literally massive. Over 800,000 acres. But beyond this quantitative measure, Big Bend is simply expansive, grand in every sense of the word. A harsh place to live, yes, where summer temperatures at low elevations are regularly over 100° F and water is scarce. But climb atop a ridge or mesa, or better yet, hike into the Chisos Mountains, and the vista painted before you is unequaled in splendor—beige plains stretching into the distance, interrupted by rocky arms and hands reaching for the heavens; red canyons carved into the bedrock, worn smooth by a million years of obstinate water; the 1500-foot Sierra Ponce cliffs that lie on the parks southern border, at whose feet meanders the Rio Grande, marking the northern edge of Mexico. (I know, you're saying, "Well where's the picture?" I have yet to capture a satisfactory shot that really would show you what I mean...still trying, though.)

Looking down on a particularly massive spring system in Big Bend. (Those are very large trees, it's just that I'm very high up.) You can see evidence of drying in the patch of dead cottonwoods downstream.

Not all of the water sources we inventory are natural. A good number of them are man-made or have had their flow altered by ranchers and other folk trying to make a living in the desert. We come across many windmill-powered wells like this one, with large holding tanks at their bases. Studies have shown that these anthropogenic repositories of water are very important to wildlife.

At this old (and dry) well site, a bereaved ranch hand painted his steed's epitaph on the side of this holding tank in 1950.

Next time we’ll head to the Sevilleta National Wildlife Refuge, explore what exactly makes a desert a desert, and look at some of the remarkable adaptations desert organisms have that allow them to persist in such a harsh landscape.

A horny toad spotted in the Gila Wilderness

Cheers,

john