The Collared Peccary

Photo by Ben Carlisle

Visitors come to the Big Bend Ranch State Park from all over the world. For many, this is their first experience with a desert, and the first animal they are likely to see and wonder about is the Javelina, or Collared Peccary. The Javelina looks somewhat like a pig and is sometimes referred to as one, but it is no longer classified in the pig family, but has its own family, the Tayassuidae. Here in Texas, New Mexico, and Arizona, Javelinas live at the north end of their range, but they inhabit the Americas to its southernmost extreme, making them the most widespread ungulate in the West.

Society and Behavior

Javelinas are social animals who live in groups, or herds of from2 to 50 individuals; most herds contain 10 or fewer members. They maintain a loose territory ranging from a few acres up to around 700 acres depending on food availability. Some writers insist that these groups are fluid, accepting new members and losing others along the way; others insist that the herd composition never changes. I personally have seen a specific individual foraging in small groups of 2 or three and in larger groups of 15 or 20. Of course, when I saw the individual with 3 others, there may have been more that I did not happen to notice …

Leadership within a herd is not necessarily associated with social hierarchy. If something disturbs them, Javelinas follow one another on a trail, usually in single file. The herd relies on scent to keep together. They mark their range and frequently rub against one another exchanging scent.

Peccaries exchanging scents

Javelinas are sexually polygamous and do not form pair bonds. Female Javelina do not “come into heat.” Mating can happen any time of year though most happens in the winter so that the “piglets” are born in the spring (gestation is 145 days). Most breeding is done by the alpha male.

Mothers guard their young closely against peccaries and other species, including people – they can be fiercely aggressive in this role. Oddly enough, sometimes the exact opposite is true. When threatened the mother may run away with the herd leaving her young behind. The young then crouch and remain still to avoid detection. As with other species, the young are most susceptible to predation.

Mother and Child

Mountain lions, black bears, bobcats and coyotes are know to prey on Javelinas.

Javelinas do not perspire and cannot evaporate moisture by panting, so they avoid heat by seeking shade under bushes and overhangs, in caves, and in self-dug pits. During cold spells they huddle together for warmth. During warm months you are likely to see them only in the early morning and evening. During cooler months you may see them during the day.

Food

Javelinas are primarily herbivorous; they eat a wide variety of fruits, tubers, rhizomes, bulbs and seeds such as mesquite beans. Here in the Chihuahuan Desert, cacti (especially prickly pears) and lechuguilla form the bulk of their diet.

Javelina eating a prickly pear pad.

They have a unique digestive system that has 3 compartments. Microbial fermentation has been reported in these compartments along with various anaerobic protozoa, suggesting that their digestive physiology is more similar to that of ruminants than to that of swine, which are non-ruminants.

Humans

Despite their fierce-looking tusks, Javelinas prefer avoiding humans whenever possible. They appear to be unconcerned with other species. At waterholes, the only species that has been observed to disturb them is the bobcat. Unfortunately, avoidance is not enough to protect them against most human encounters. Collared peccaries are subsistence animals for several indigenous tribes in Central America where the meat is a major source of protein. Their hides are thin, strong, and marked with bristle-holes that makes them useful for “pigskin” jackets and gloves. During the late 19^th and early 20^th centuries one firm (Cohen & Company) handled over 30,000 hides in a single season. Most of this trade went to Europe where the skins were used for gloves and the bristles for brushes. The hides were used as barter in many trading posts along the U.S.-Mexico border.

A Used-to-be-Javelina

Javelina are now protected as game animals and their populations have largely recovered from the low levels of the past. They readily adapt to having humans around them and are quick to discover the treasures of table scraps, birdseed, bread, and pet food that humans often leave around them. Here in the Big Bend Ranch State Park they have learned to overturn quite heavy steel trashcans and work off the lids. In the national park they will walk right up and wiggle their little pink noses at you. Sadly, many visitors cannot resist these approaches and will give them “treats.” I can personally attest to the fact that Javelina in the Big Bend National Park know what chocolate is, and they like it!

Here at the park, many visitors enjoy watching them from the front porch of the “bunk house” and in the back yard of the “big house.” Though they are accustomed to visitors, photographers will want long lenses and high ISO settings to photograph them well – Javelinas still avoid humans when they can. Perhaps they remember those glove and brush days of the past!

Colors of Bentonite

Bentonite is a common clay material with an uncommon number of uses. Bentonite is widely distributed – it is particularly abundant in the Big Bend region of the Trans-Pecos because past volcanic activity produced such abundant supplies of the materials from which it is made. Bentonites were formed by mechanical and chemical weathering of volcanic materials such as glasses and tuffs. (Tuffs are made of volcanic ash.)

Volcanic Tuff at Big Ben National Park

Being a clay, bentonite weathers quickly, constantly exposing fresh material at the surface. Two properties of bentonite make its deposits visually distinct – it expands dramatically when wet, and it readily adsorbs a wide range of metals and other minerals. Bentonite’s constant expanding and contracting destroys the root systems of seedlings and/or plants such as cacti that have widespread, shallow roots. The result is that very little grows on exposed bentonite deposits – bentonite hills are completely bare on top.

Plantless Conditions on Top of Bentonite

On the other hand, bentonite readily adsorbs a variety of minerals which give it color. So most deposits have wide bands of varying colors. In West Texas, reds, yellows, blues and greens are common colors.

Because it weathers so fast, bentonite badlands are usually characterized by numerous canyons, ravines, gullies, hoodoos and other such geological forms. The combinations of weird shapes and colors give bentonite badlands a beauty all of their own.

Canyon Made of Bentonite

Although its exact chemical composition is variable, the properties that make bentonite useful, and beautiful, are the result of its physical structure. It is composed of a number of layers, each approximately 10 angstroms thick, and each consisting of two tetrahedral and one octahedral unit. This structure is responsible for three important characteristics of bentonite: the ability to absorb large amounts of moisture, the ability to exchange ions of one element for another, and the property of thixotropy.

Physical Structure of Montmorillonite

Water absorption – Bentonite usually occurs in the form of tiny flakes ranging in length from 0.01 micrometers to 10 micrometers. The flakes aggregate to form thin particles. These particles have truly extraordinary surface areas. Twelve grams of bentonite have the surface area of a football field. So bentonite can absorb huge amounts of water and other polar fluids. The water accumulates in the spaces between layers. These spaces can grow to 10 times the width of the layers surrounding them, and the mineral as a whole can swell up to 20 times its regular volume.

Cation exchange – Bentonite is always electrically unbalanced by atoms that have replaced aluminum – elements such as magnesium, iron, or calcium. The result is a positively charged space between the layers. This space becomes filled with cations (negatively charged particles) which are positioned, but weakly held, near the tetrahedral layers and which serve to balance the charge. The cations are extremely mobile and can be replaced or exchanged with almost any other cation. This ability to exchange cations is an important characteristic of bentonite.

Thixotropic Grease

Thixotropy – When saturated with water, bentonite becomes thixotropic. Thixotropy is the property of certain gels or fluids that are thick (viscous) under normal conditions, but flow (become thin, less viscous) over time when shaken, agitated, or otherwise stressed. This characteristic makes bentonite ideal for use in drilling muds and a wide variety of other construction applications where it is applied as a fluid and expected to remain in place indefinitely. Here is a picture of an thixotropic lubricant containing molybdenum disulfide; the molybdenum provides lubrication in high-temperature situations where parts of the lubricant components may fail.

Uses

Typical Storage Pit for Drilling Mud

Bentonite is used as a sealing agent to seal landfills, tunnels, dams, and other water agents. It is added to concrete and mortars as an admixture. When used in drilling muds, bentonite lubricates cutting heads and seals cracks and other leaks around pockets of water and/or other fluids that are not the primary object of the drilling. It is widely used in West Texas to line stock ponds, settling tanks, and other open-air fluid containers where leakage to the ground below is undesirable. Probably the cattle and oil industries are the largest consumers of bentonite in this area.

Bentonite is sticky when damp and very resistant to high-temperature degradation which makes it ideal a use as a binder in moulding mixes. The metallurgy industries are major buyers of bentonite.

Bentonite is used as a plasticizer in ceramic materials and in the production of ointments, tablets, medications and cosmetic creams. It is used as a thickener in paints, as a binder in granulated feed-stuffs, as a strengthener in plastics, rubber, explosives, glass and mineral fibers and fertilizers.

The food industry uses bentonite for cleaning, decolorizing and stabilizing vegetable and animal fats and oils. Wine makers, juice makers and brewers use it to stabilize and clarify their products.

During the past 20 years, bentonite has been used by the nuclear industry where it is compacted to high densities and applied as blocks between the canisters and surrounding rock where it takes up water and swells to completely fill spaces. Even if new spaces open, bentonite will swell to seal the gaps. This prevents radiotoxic nuclides from entering the biosphere.

Kitty Litter

Cat in Litter Box

Perhaps the application most familiar to everyday householders is in kitty-litter. Bentonite absorbs urine and helps deodorize solid waste. More than two million tons of bentonite pass through American kitty litter boxes every year. And you’re likely to find kitty-litter, or something like it in garages where it is very useful in cleaning up oil spills.

There is a marvelous exposure of bentonite on the western side of Big Bend National Park. The colors and shapes of these hills make them endlessly fascinating to explore. When I’m hiking out there though, somehow I just can’t seem to forget that these exotic canyons are actually made of kitty-litter! Who would have thought?

Bentonite Badlands

Shameless Promotion

Friday, February 24, the Big Bend Ranch State Park begins the first in a series of camping/photography tours that take you to some of the most rugged, remote, and scenic locations in the park. These locations are only accessible via primitive roads that are impassible to all but 4-wheel drive, high-clearance vehicles.

View from Guale Mesa Campsite

The tours are intended for photographers who would like to work in the park but who lack the proper vehicles for reaching the best sites. I will be available to answer technical questions and provide help where needed, but there are no classroom activities – just two days of uninterrupted photography.

This month’s tour is to Guale Mesa. You’ll camp atop a high bluff that overlooks Rancherias canyon on the east, La Guitarra Mountain to the south, and the Lower Guale Mesa to the southwest. A short side trip on Sunday morning will give you an opportunity to photograph scenic Tapado Canyon at sunrise. The view southwest from the canyon rim stretches all the way to the Sierra Ricca mountains in Mexico. Blue-green walls line the canyon walls to the northwest, and the rim itself is quintessential Chihuahuan Desert. Few people have even seen this magnificent sight, much less photographed it!

View of Tapado Canyon

Price for the tour is $350; it includes one night’s lodging at the Bunkhouse, one night’s camping “on location,” all meals and transportation. The tour is limited to 6 photographers – the perfect size for a campfire supper and friendly conversation. You can make reservations by calling 432-358-4444. This price will have to be pre-paid.

Note: you must bring your own camping supplies, i.e. tent, cot, sleeping bag, pillow. We are only providing the ride to the location, food, and the atmosphere.

Another Note: I’m not being paid for this; it’s all voluntary. I’m just trying to help the park. If you know anybody who might be interested, please let them know. Thank you!

Fluffgrass

One of the most common questions people ask me about plants in the Big Bend Ranch State Park regards a small grass known as Fluffgrass. Their curiosity is understandable; over 20 years ago, when I was hiking in the park for the first time, a cold front bringing freezing temperatures and on-and-off rain passed. I wasn’t well prepared for this kind of weather so I was pretty cold. When I passed Cerro La Guitarra, without my glasses, I honestly thought there were patches of snow on the ground! This image, taken from a badly faded and color-shifted negative, records the scene.

Fluffgrass on Guale Mesa

A closer inspection revealed that the white spots were a plant, but I had no idea what it was. Today I know it as Dasyochloa pulchella, the only species in the Dasyochloa genus. It is a perennial bunchgrass that forms small tufts just a few centimeters high with clumps of short, sharp-pointed leaves. Nobody seems to know much about it, or care much for it, but it is one of the most commonly occurring grasses in the Southwest.

This grass is readily noticeable, particularly when the sun is low and behind it, for it fairly glows, easily outshining everything else around. When fluffgrass drops its seeds, the translucent bracts remain on the plant, catching the light and giving the appearance of glowing.

Glowing Fluffgrass

The grass is regularly described as having “poor forage value.” When young and actively growing the plants are covered with a bluish-white down that may be objectionable to grazing animals. Later, when the plants mature, the leaves become harsh, wiry and sharp pointed. Livestock and wildlife generally avoid it; if you see it browsed, you know that times are hard.

What the animals don’t eat we can nonetheless enjoy, for this little grass is attractive at nearly every stage in its life cycle. It is particularly pretty when young for its bluish-green foliage is covered with a soft cottony down.

Young Fluffgrass Plant (Image ©Phillip Ruttenbur )

The nature of the down is not known – some experts claim it is composed of excreted mineral salts. Others say that it is made of carbohydrates. Whatever its composition, the “wool” is soluble in water and washes away with the first rain. Sometimes the down appears to be made of distinct fibers. At other times, the material looks much more amorphous.

Amorphous Looking Fluffgrass Fuzz

The nature of the wool is not known – some experts claim it is composed of excreted mineral salts. Others say that it is made of carbohydrates. Whatever its composition, the wool is soluble and washes away with the first rain.

As fluffgrass matures, it loses its bluish cast and becomes a bright green.

Maturing Fluffgrass Plant

The inflorescence is one or two centimeters long and bears spikelets which are pale in color, sometimes striped with red, purple, or green. They are rather flattened and look a bit like small fans.

Fluffgrass Inflorescence

For me, fluffgrass has become one of the Chihuahuan Desert’s many little pleasures. The plant’s constantly varying appearance, bright glow in the winter, and preference for open areas where nothing else grows, makes it a welcome sight. Its ubiquitous presence is a constant reminder of life’s resilience, even in the most difficult of environments. Look for it the next time you hike in the Trans-Pecos. It’s worth your attention.

The Beautiful Texas Madrone

Madrone on the Pinnacle Trail. Big Bend National Park

With Fall approaching, one of Texas’ most beautiful trees, the Texas Madrone reaches the height of its beauty as it puts forth its crop of beautiful red berries, often growing in hand-sized bunches and completely covering the tree. These lovely berries give the tree it’s first scientific name, “Arbutus,” which is a Latin word meaning “Strawberry Tree.” The name Madrone comes from the Spanish word madroño which means the same thing. In the winter, the combination of green, white, and red wood, bright green leaves, and large red berries makes this tree a joy to behold.

In the spring, the tree is covered with large bunches of urn-shaped, cream-colored flowers which fill the air with an exquisite fragrance.

Bunches of Tiny Urn-Shaped Blossoms

Small groups and individual trees can be found in many places. For West Texans, the best place to see them is in the Chisos Mountains and the Guadalupe Mountains.

You can see many Madrones along the road to the Basin, but without doubt, the best place to find them is in the Guadalupe’s. There are surviving Madrones on the trail leading almost due north from the Pine Springs campground. These Madrones are atypical in that they grow mostly in isolation, giving this trail a distinctly “savannah” look and feel.

The Devil’s Den trail passes through stands of this tree, and is a beautiful visit any time of the year. But the very “best of the best” location is McKitrick Canyon.

Madrones Line the Trail in McKittrick's Canyon

In the shelter of this canyon, starting in early fall, the Maples begin to change color and Madrones line the trail with their fruit-laden branches. A fall hike through this canyon is an experience you will never forget. Trust me on this.

Madrone Growing in McKittrick Canyon

The Texas Madrone is not normally a large tree – it reaches 20 to 30 feet at the most. Madrones are usually multi-trunked with tortuously-shaped limbs that are smooth to the touch. The limbs spread out to give the tree a canopy of dark, leathery leaves that stay green year round. In the spring to mid-summer blooming season, the tree produces large clusters of creamy white, bell-shaped blossoms that fill the area with a delicious fragrance.

Madrone in Bloom

The velvety-smooth wood changes appearance throughout the year. In the spring it usually runs from white to a pale green though it may sometimes be a light burgundy.

The bark often feels like skin -- soft and smooth to the touch

As the year progresses, the old bark darkens into shades of brown and red and begins to peel off. As it falls away, it reveals the younger wood underneath which may be any color between white and bright red.

The Peeling Bark is Often a Brilliant Red

In fall, the tree puts out its crop of berries.

The Sweet Red Berries Look Like Small Strawberries

In the winter, the combination of green, white, and red wood, bright green leaves, and large red berries makes this tree a joy to behold.

Mature Madrone With Fruit

Despite the Madrone’s great beauty, it is seldom seen by the general public. There are several reasons for this.

• The Madrone is a fairly rare tree in North America, growing only on the Edwards Plateau, in far West Texas, and in southeastern New Mexico.
• Its’ preference for montane habitats keeps it out of the view of the general public though hikers and backpackers are usually familiar with it.
• It is not very good at reproduction. The seedlings are palatable to deer so few seedlings survive to grow to maturity.
• It is extremely slow growing – it can take over a century for a Madrone to fully attain an adult height of 20 to 30 feet.

These factors, combined with declining habitat, rising temperatures, and decreasing rainfall are causing Madrone populations to decline.

It is fortunate that this tree is little used for utilitarian purposes. Native Americans considered the tree sacred and refused to burn it despite the excellent fire it provides. The wood is reddish-brown, hard, heavy, and close-grained. It is dimensionally stable, easily worked and it takes a fine polish; however, it is brittle and not very durable. In most of its historical applications, Madrone wood has been replaced by cheaper synthetic materials.

Madrones are more plentiful in Mexico than here, and they are used somewhat more. Leaves and bark are used as astringents and diuretics, bark and roots are used to make organic dyes, and the wood is sometimes used to make stirrups.

The berries are used most. Birds such as trogons, jays, and band-tailed pigeons eat them – Black Bears are quite fond of them.

The Main Trunk Shows the Scars Left by Foraging Bears

If you hike in the Chisos you will see many madrones that carry deep scratch marks from the claws of bears climbing to get the fruit. Though the fruit tastes rather bland to modern palettes, it can be made into jellies and jams. The Tarahumara Indians of northern Mexico make an alcoholic beverage from fermented Madrone berries and flavor tortillas with the tree’s flowers.

One would think that any tree this beautiful would be avidly cultivated, but that is not the case. Texas Madrones are notoriously difficult to plant and grow. Twenty years ago it was widely believed that it was impossible to grow one from seed, or to transplant one from the wild. In 1975, the Texas Horticulturalist magazine reported on an experiment that was conducted to try to germinate madrone seeds. Of the 10,000 seeds planted, researchers succeeded in germinating only 2 seeds.

In the past 20 to 30 years, growers have gotten better, and today a handful of nurseries, mostly in the Kerrville area, have mastered the business; fair-sized Madrones may now be purchased for home gardens.

We now know enough about this tree’s needs that amateur gardeners can reasonably expect to be able to grow them. Should you decide to try, here are a few facts you should keep in mind.

Seeds need to be planted shortly after harvesting. If they remain moist, germination can begin within 7 to 14 days. Once dried they rapidly lose fertility. After only 6 months of cold dry storage you can expect fewer than 40% of seeds to be fertile. After 2 years fertility drops to around 4%.

Seedlings grow best with a 12-hour photoperiod at daytime temperatures of 81 degrees and nighttime temperatures of 64 degrees. The soil should be well drained and run close to a neutral pH (6.8 to 7.2).

Good growth occurs at 60 to 70 percent relative humidity at a light intensity of 6,500 to 10,000 lux.  At higher light intensities, growth may be reduced by photo-bleaching of chlorophyll, though high soil moisture may ameliorate this problem. Under ideal conditions you can expect germination rates of from 20% to 90%.

Madrones have a poorly developed fine root system and what they have is easily damaged. Worse, even slight damage to the root system is usually fatal to the tree. Growers should take every precaution to avoid root stress – this is not one of those trees you can take home, rip off the plastic bag, fluff up the roots and toss into a nice-sized hole. Rather, bags should be removed with the utmost care, the tree lowered into a hole of exactly the size of the root ball, and additional soil gently sifted over to fill the hole (no tamping please). Home growers may benefit from starting young trees in biodegradable containers that can be lowered into planting position without disturbing the tree’s roots.

Much remains to be learned about this fascinating tree, but its best hope for survival probably now lies with home horticulturalists who take the time to learn how to grow it, and who share their knowledge with others – without our help it is unlikely that this tree will continue to do well here in the northern Chihuahuan desert.

Plant Adaptations to Desert Conditions

The Chihuahuan Desert is the most thickly vegetated desert in North America. Indeed, if you visit in during the rainy season you might wonder why it is called a desert at all.

It hardly looks like a desert at all during the rainy season.

Though for the most of the year the Chihuahuan Desert is not green, even in the most arid, empty spaces hikers must watch their footing carefully for most desert vegetation is well armed and intimate encounters are best avoided.

In dry periods the land is brown and most of the plants look dead. But these plants aren’t suffering. They’re not “struggling to survive.” They’re just doing what desert plants do – quietly waiting for the next rain.

The vegetation here is dried out, but still quite alive

Desert plants have developed a number of strategies for living with the protracted dry periods and seasonally high temperatures that characterize the Chihuahuan Desert. Some approaches are shared by most desert plants – others are more specialized. Among specialized adaptations, most plants have followed one of three different paths to success: succulence, tolerance, and evasion.

Cacti swell almost to bursting when water is abundant

Succulent plants are water hoarders. They store water in stems, roots, or fleshy leaves in special structures that are good at retaining moisture. All cacti are succulents, but many non-cacti desert plants use the same adaptation. Succulents include agaves, aloes, and many euphorbias. Aside from storing water in their tissues, succulents have use other specializations to succeed.

Succulents must absorb large quantities of water in short periods of time, but they cannot absorb water from soil that is not wetter than their own interiors. Since desert soils are rarely and only briefly wetter than the interiors of any plant, nearly all succulents have extensive, shallow root systems. These shallow roots come to life quickly at the slightest sign of rain, and they harvest water from the soil rapidly and efficiently. Most succulents have roots less than 4 inches below the surface with feeder roots that lie within half an inch of the surface. They spread out far from the mother plant – for example a two-foot-tall cholla may have roots over thirty feet long!

A succulent such as a cactus looks very much like a bag of water to most thirsty animals, so succulents guard their water fiercely. Most are spiny, bitter, or toxic, and often all three. A few unarmed, non-toxic species exist, but they are usually confined to extremely inaccessible locations such as vertical cliffs or within the canopies of other spiny plants. The plant’s water is usually bound in extracellular musilages and inulins (soluable fibers) that release water only reluctantly, so even if part of the plant breaks off, it stays moist inside for a long time. Waxy cuticles make them practically waterproof when their stomata are closed; those that have leaves shed them quickly when the soil dries out.

Many succulents also employ a special type of photosynthesis known as CAM for Crassulacean Acid Metabolism. Instead of synthesizing carbohydrates, they synthesize Crassulacean acid during the day while their stomata are closed and store it in their tissues. At night, when temperatures are lower and humidity higher, they open their stomata and break down the acids into carbohydrates using carbon dioxide from the air. CAM is extremely efficient at using water. Plants that use it consume only about 10% of the water other plants consume to synthesize the same amount of carbohydrates. The overall rate of photosynthesis is slower however, so CAM succulents are usually slow-growing.

CAM photosynthesis often gives the plant a reddish color

CAM plants are able to “hybernate” during dry times, recycling oxygen and carbon dioxide to conduct very low-level photosynthesis. Since they have not gone completely dormant, CAM plants can resume growth within 24 to 48 hours after a rain. An agave can sprout new roots within 5 hours of a rain, whereas dormant shrubs usually take two weeks or more to revive.

Just after a rain, this fern is partly hydrated, partly dormant

Instead of storing water, some plants simply dry out, lose their leaves, and appear to be dead. In this condition, drought-tolerant plants reduce their metabolisms to near zero when it is dry, but they are ready to resume growth as soon as the rains arrive. Some shrubs can become dry enough to use for kindling, yet they are alive. They often shed leaves during dry spells, and those that keep them usually have resinous or waxy coatings that retard water loss. Desert ferns can become completely dehydrated without dying.

Drought-tolerant plants usually have more extensive root systems than their water-loving relatives, with roots extending to 2 or 3 times the size of the canopy. In addition to breadth, many grow very deep roots to reach moister levels of soil. These deeper roots can sustain growth for many weeks after a rain.

Because drought-tolerant plants rely more on deeply buried moisture, they take longer to revive than succulents. In creosote bushes, traces of green may appear early after a rain but fully active new root systems and new leaves usually take 2 or more weeks to develop.

Desert Marigolds may wait out a drought as seeds

Some plants simply evade drought. These plants die during dry periods, and rely on seeds germinating during future rains to preserve the species. In terms of species count, drought-evasive plants are the most successful adapters to desert climates. Seeds have almost no metabolism and possess great resistance to environmental extremes. Seeds appear to be remarkably “intelligent.” Most will only sprout under very specific circumstances such as a minimum amount of rain, a particular season, a temperature window, specific soil types and conditions and frequently some combination of the above. Even under the best of circumstances, not all seeds will germinate, for some remain dormant. Some bluebonnet seeds, for example, will not sprout until they have been in the ground 10 years. How seeds manage these remarkable feats is not clearly understood.

Some plants are adapted in several ways. Ocotillo, for example, uses CAM metabolism and a broad, shallow root system like succulents. But it drops its leaves and dries out like a drought-tolerant deciduous shrub. Semi-succulent yuccas store some water in their leaves but also put down deep roots to obtain most of their water.

Aridity affects many conditions important for plant survival. The clear dry air allows unfiltered sunshine from dawn to dusk. The solar radiation produces very high temperatures which are lethal to non-adapted plants. On the other hand, the dry air loses heat quickly at night allowing the temperature to drop dramatically.

Schott's Acacia has very small leaves

Nearly all leafy desert plants sport small leaves. At first it would seem that small leaves would not be useful. After all, they have a much higher surface-to-volume ratio than bigger leaves and so should lose water more rapidly. But this adaptation avoids overheating, and thus, water loss. Large leaves require transpiration through open stomata to keep cool – this is not an option during the hot months in the desert. Gardeners know that tomatoes must be shaded in desert environments or they will burn. They cannot evaporate water fast enough to keep cool. But small leaves can stay below lethal tissue temperatures of about 115 degrees on a calm day with stomata closed.

Honey Mesquite remaining green during a dry period

Finally, there are some desert plants that are not really adapted to dryness at all. They survive by growing long roots that remain in the water table at all times. The mesquite is an example of such a plant. Some sources say that Mesquite roots can descend to 200 feet, others say not so deep. The average is close to 40 feet – mesquites will die if the soil dries to this depth.

The Chihuahuan Desert is uniquely endowed with a rich variety of plant life, and the phases of their lives are easily observed. Watching plant life adjust to the seasons here can be one of the unique pleasures of living here in West Texas.

A Natural Garden of Desert Plants

Lichen

Lichens must surely be one of the most unusual organisms on the planet for they are not really a true species but a community of two or three completely unrelated organisms living in the same skin. The organisms living together are symbiotic with one another – that is, none can live without the other.

The dominant partner is a fungus. Because fungi cannot make their own food, they usually live as decomposers or parasites. But in lichens, fungi maintain symbiotic relationships with other species that can make food. The symbiont partners make food by photosynthesis; they are usually an algae, a cyanobacteria, or both. Up to 18,000 species of fungi have been “lichenized” and about 40 genera of algae and cyanobacteria are found in lichen partnerships.

Several different-colored species of lichen living as neighbors

Lichen primarily reproduce vegetatively, so most lichens start life complete with all their parts. Any lichenized fungus born without its symbionts will die unless it can acquire them in some other way. Not just any symbiont will do – a lichenized fungus can live with only one species of algae or bacteria; the reverse is also true.

Fungal partners tend their symbionts by providing them with a protected environment, organizing them into patterns that permit optimum photosynthesis, and exchanging metabolites with them to improve their nutrition. They harvest their crops by secreting chemicals that cause the algae to “leak” nutrients to the surrounding tissue or grow minute tendrils that pierce the symbionts’ walls to extract food. The harvest is pretty good. Up to 80% of the photosynthesized carbohydrates go to the fungus. If cyanobacteria are present, the fungus extracts nitrogen and other biologically useful compounds it could obtain in no other way.

Lichens have been around for at least 600 million years. Their hardiness is legendary. They can live in the Arctic tundra and in the intense heat of Death Valley. They can dry out completely without being harmed, and are practically immune to ultraviolet radiation. In 2005 the European Space Agency carried lichen into outer space and left them outside the spacecraft for over two weeks. When returned to earth and watered, the lichen resumed photo­synthesis as if nothing had ever happened.

Lichen colonies can be quite large and can quite literally change the appearance of the landscape. In this photo, lichen have almost completely masked the red color of the rocks with their own bluish-grey tint.

Lichen have almost completely obscured the rock's red color with their own blue-grey tint

Both wildlife and people eat lichen. Mule deer have a taste for them; their foraging often creates a visible browse line on tree trunks. The Japanese use lichen in many traditional foods, and hikers sometimes eat them as survival food. Many lichen turn up in commercial products such as ointments, deodorants, tonics, and expectorants. One chemical which is derived from lichen, is the active ingredient in litmus paper. It changes color according to pH. Home swimming pool owners around the world use litmus paper, made with lichen extracts, to monitor the condition of their pool water.

Over 50 species of birds, including many hummingbirds, use lichen in their nest building. The female Anna’s Hummingbird covers the outside of her nest with lichen to camouflage its presence. A few insects also use lichen for camouflage. And, of course, moths and butterflies have evolved to mimic the colors and patterns of lichen to camouflage themselves. The military has noticed the patterns and colors and realized that the appearance of lichen changes very little through the seasons. A new, patented, camouflage pattern is now being used. It is claimed that this camouflage is exceptionally difficult to detect.

Lichen even play a significant role in geological processes. They produce acids which dissolve rock and help break it down. Some lichen attach themselves to rock by sinking root-like tendrils into the rock. These tendrils regularly grow as much as 8 inches beneath the surface. As they swell and contract, they create fissures in the stone. Water flows into these fissures, hastening the erosional process.

Lichens grow in roughly four shapes –

Folios Lichen

Folios lichens are flat, leaf-like organisms. You are most likely to notice them growing on tree limbs or trunks after a rain because the edges tend to curl up then and reveal the “leafy” structure.

Crustose lichens grow like crusts on the surface or between the crystals of volcanic rocks, or buried in tree bark. The brilliant red, yellow, and orange lichen you see growing in the Davis Mountains are mostly crustose lichens.

These crustos lichens grow in mineral-rich cracks on the rock's surface

These fruticose lichens look like a miniature rain forest

Fruticose lichens look like miniature shrubs. They often resemble masses of string hanging from trees or other plants.

This Squamulose lichen grows on the ground

Squamulose lichens are scaly and are usually comprised of numerous small rounded circles. Our “ground lichens” are of this type. On loose soil they sometimes appear to be growing on tiny mesas or pedestals. These elevated patches result when rain washes soil away everywhere except under the lichen.

Some lichen have such pronounced antibiotic properties that they are commercially valuable. Lichens from the genus Usnea are used in ointments and other products sold as aids to healing wounds. Lichens may be found in deodorants, laxatives, and expectorants. Ongoing research is beginning to indicate that some lichens may be useful against certain cancers and viral infections.

Lichens are one of the many “little things” that make exploring the Chihuahuan Desert interesting and rewarding.

A Small Patch of Color in the Chihuahuan Desert