Welcome to the Desert Discovery Trail at the Chihuahuan Desert Nature Park. There is no need for hiking boots, sunscreen, or water on this virtual tour!
During this tour, you will learn about the Chihuahuan Desert, its plants and animals, the geology, and its early human inhabitants. ENJOY!
Stop 1 - The Chihuahuan Desert
Stop 2 - Desert Plant Adapatations
Stop 3 - Erosion and Soil Formation
Stop 4 - Desertification
Stop 5 - Desert Animal Adaptations
Stop 6 - Humans in the Desert
Stop 7 - Effects of Slope & Aspect
Stop 8 - Geomorphology
Stop 9 - Invertebrates
Stop 10 - Geology
Stop 11 - Lichens
Stop 12 - Animal Evidence
Stop 13 - The Jornada Basin
The Chihuahuan Desert is the largest of the North American deserts. From where the park is located, it extends almost 200 miles (322 km) north and 600 miles (966 km) south. Most of the 250,000 square mile desert is located in the state of Chihuahua, Mexico. This is where the desert got its name.
The climate of the Chihuahuan Desert is relatively mild compared with other deserts, partially due to an elevation that averages 4,500 feet (1,372 m) above sea level. Summers are hot, while winters can be cold. The wet season (July through September) brings more than 50% of the average annual precipitation. In this region of the Chihuahuan Desert, the average annual precipitation is 8.9 inches (22.6 cm).
The Chihuahuan Desert is one of the most biologically diverse deserts on the planet. It ranks #1 among deserts for the number of aquatic species and the number of mammal species. More than 300 species of cacti are found here.
Crucifixion thorn has green stems where photosynthesis takes place.
We have four dominant plants of the Chihuahuan Desert in the Nature Park - creosote bush (Larrea tridentata), honey mesquite (Prosopis glandulosa), tarbush (Flourensia cernua), and crucifixion thorn (Koeberlinia spinosa). These plants, along with other plants of the Chihuahuan Desert, have developed numerous adaptations that allow them to cope with the extreme temperatures, low water availability, and high solar radiation found in this environment.
Roots and leaves of the plants are often specialized for desert conditions. For example, perennial grass roots that are shallow and dense collect water quickly when it rains. Other plants, like honey mesquite, have deep root systems that can tap into longer-term water sources. Since leaves are a primary source of water loss, it is not uncommon to find desert plants with small leaves (e.g., creosote bush) or with leaves so small they look like they have no leaves at all (e.g., crucifixion thorn).
The fishhook barrel cactus (Ferocactus wislizeni) has accordion pleating that allows it to expand and store large quantities of water when it is available. Finally, cacti and some succulents use a special type of photosynthesis that functions only at night when temperatures are lower and humidity is higher, so plants lose less water to evaporation.
The smaller soil particles have washed away leaving larger rocks behind.
The Nature Park has at least eight different types of soil. The differences exist because of the variety of ways that the five soil forming factors (climate, organisms, topography, parent material, and time) interact. These factors, acting together, form soil by altering the physical and chemical nature of the original geologic deposits and rock.
At this stop, the steep slope (topography factor), the small amount of vegetative cover (organism factor), and the heavy rainfall intensity (climate factor) cause most of the water to run off. Only a small amount of water goes into the soil. The sand, silt, and rocks (parent material factor) are less likely to break down through chemical weathering processes than in a soil that stays moist for long periods (time factor). As a result, this soil contains more rocks than it would if it were wetter.
Due to erosion, the roots of this grass are now entirely exposed.
Prior to the introduction of domestic livestock, many piedmont slopes within the Nature Park would have supported several species of grasses with scattered shrubs. Grazing and drought reduced the amount of grass and its capacity to hold soil in place.
Runoff water strips away small soil particles (sand, silt, clay) from the unprotected soil and leaves behind the larger gravel that already existed in the soil. Over time, this produces an erosion pavement of gravel that functions like armor to protect the soil from further erosion. The fertile topsoil that once supported grasses is now gone and nutrient-poor subsoil layers are at or near the surface.
Caliche formed on a rock.
The white coating on the rocks is calcite, a mineral composed of calcium carbonate (CaCO3); some people call this caliche. It is a chemical material similar to the hard water deposits that are left around faucets in your house. Calcite plugs the pores between sand and gravel, making it "nature's concrete". Calcite forms beneath the soil surface, giving soils of arid regions a whitish or gray color. It has been accumulating in this soil for more than 250,000 years. The presence of the white coating at or near the soil surface is evidence of soil erosion.
This banner-tailed kangaroo rat is distinctive with its black and white tail.
Desert animals have a variety of physical adaptations to prevent overheating and reduce water loss. For example, jackrabbits have long ears and insects have impermeable body coverings. Many behavioral adaptations (such as being nocturnal and living in burrows) also enable animals to survive in the desert.
The Merriam's kangaroo rat (Dipodomys merriami) is one of the three kangaroo rat species found in this area. Other species are the banner-tailed kangaroo rat (Dipodomys spectabilis) and the Ord's kangaroo rat (Dipodomys ordii). Specialized nasal passages and kidneys reduces water loss from the body.
Spadefoot toads escape the harshest desert conditions by living underground in a state of dormancy during most of the year (estivating). When heavy rains arrive, they come to the surface to feed and reproduce quickly before the water disappears again.
Many rodents live in burrows to escape the heat of the day. Other animals, such as snakes and lizards, will occupy abandoned burrows in order to take advantage of the cooler temperatures inside
Stone tools called manos and metates were used to grind corn and mesquite beans into flour.
Stone tools called manos and metates were used to grind corn and mesquite beans into flour. People and their associated changes to the environment have been here for at least the past 12,000 years. Initially, the climate was cooler and wetter. As conditions became warmer and drier, short-term fluctuations in the climate had major effects on all life - plants, animals, and people. The earliest cultures in this area were present from about 10500 - 6000 B.C. during the Paleoindian period. People were hunter-gatherers, living solely from wild game and plants. They traveled extensively to pursue herds of animals such as mammoths, bison, mastodons, and giant ground sloths.
Pottery shards from clay fired pots indicate increased reliance on agriculture for the early people of this area.
During the Archaic period, from 6000 B.C. to 250 A.D., the large animal species, except the modern bison, were gone. The climate became warmer and drier, and some of the first desert plants appeared. Grinding stones (manos and metates) became more prominent, indicating an increase in the processing of wild plant seeds and nuts.
Domesticated plants (corn, beans, and squash) came into use by 3,000 years ago. By no later than 1,700 years ago, fired clay pots, a technology from Mexico, began to be used, marking the beginning of the Formative period (A.D. 250 - 1450). The advent of pottery coincided with increasing reliance on agriculture and increasing sedentism and population sizes.
By about 1450 - 1500 A.D., pueblos throughout many areas of the southwest were abandoned, pottery traditions ceased and the number of people dropped significantly. Political strife and environmental degradation are two possible reasons for this abrupt abandonment. What became of the people in southern New Mexico is unclear.
South facing slope at the Chihuahuan Desert Nature Park.
North facing slope at the Chihuahuan Desert Nature Park.
Water availability and temperatures of desert mountain slopes vary with slope angle and aspect (the direction the slope faces).
On the south facing slope of the hill at the Chihuahuan Desert Nature Park, we can see the high abundance of large prickly pear cactus, ocotillo, and banana yucca. These drought-tolerant species require well drained soils so their roots will not have rot damage from too much soil moisture.
On the north facing slope, creosote bush predominates and there are few cacti and other succulents.
This fan-piedmont gently slopes eastward from the Dona Ana Mountains.
The land surface is sculpted through time by wind, water, and earthquakes. Landscapes with similar shapes, the same origin and the same age are called geomorphic surfaces. For example, the fan-piedmont (in the photo to the right) is a gently sloping landform that extends from the base of the Doña Ana Mountains to the basin floor. The mountains are the source of the gravel, sand, silt, and clay that were carried by water to form the fan-piedmont.
Vinegaroons (an arachnid) are just one of the invertebrates that you can see in the desert.
There is a mind-boggling array of invertebrates essential to providing critically important services, including cycling energy and nutrients though the system. They carry out these vital functions by eating and being eaten, pollinating most of the desert's plant life, distributing seeds, creating holes that aerate the soil and increase water infiltration, and recycling dead plants, animals, and animal wastes.
Large harvester ants (Pogonomyrmex rugosus) and honey pot ants (Myrmecocystus spp.) are just two of the species in a diverse set of invertebrates (animals without backbones) that live here.
These rocks have been weathered away over millions of years.
Large boulders sometimes appear to be peeling away layer by layer. This is called exfoliation and is an example of a physical rock-weathering process. Water moves into cracks in the rocks, freezes and expands, causing the rock to flake apart. Expansion and contraction from hot desert days and cold nights can also cause the rock to split. As the edges of the coarse-grained monzonite rock break away, it develops into rounded boulders. The process of exfoliation is the first step in soil formation from these large boulders. Physical, chemical, and biological processes will continue to break down the flakes of exfoliated rock into soil-sized particles.
The formation of the different rock types and the mountainous topography within the Chihuahuan Desert Nature Park resulted from two different volcanoes.
An easy way to remember what forms a lichen - "Alice Algae and Freddy Fungus took a lichen to each other."
There are bright yellow, red-yellow, and green patches on the rocks along this part of the trail. These brightly colored lichens are actually two organisms - fungus and algae - in one. The association between the organisms within lichens is so complete that scientists give genus and species names to the lichens; the different colors of lichens you see are different species.
Within a lichen, the fungus provides a structural web that protects the alga and provides a suitable environment. In turn, the alga photosynthesizes and provides the fungus with food. When moist, lichen release small amounts of acid that dissolve the rock. This is called chemical rock-weathering and is extremely slow.
Sometimes you can find "moss rocks" for sale or find them out in the wild. This is not moss but lichen. Remember, lichen is a living organism and can die if removed from its natural location.
Living underground gives the packrat the advantage of cooler temperatures and higher humidity in a hot, arid climate.
Spotting animals in the desert is dependent on the weather and time of day. In the summer, the middle of the day is not the optimal time for animals to be out. While air temperatures may be pushing 100°F, the ground temperature could be over 140°F! But even if you don't actually get to view any animals, you can tell what lives there by finding evidence of animals such as bite marks on plants and burrows.
Under prickly pear cactus and mesquite, you can find piles of sticks, cactus pads, and other materials. These piles are called middens and are created by packrats (also known as woodrats). Middens are occupied by successive generations of solitary packrats and are often also home to beetles, crickets, and a variety of small mites and collembolans (springtails).
Some packrat middens are more than 50,000 years old and have been important for making paleoecological reconstructions of an area. The leaves, seeds, bones, and other debris collected for the midden are often found well-preserved by crystallized packrat urine. Examining these fossilized middens tells scientists about the plant community and climate of the area thousands of years ago.
The view from Vista Bench at the Nature Park gives you a panoramic view of the (from left to right) San Andres Mountains, San Augustine Mountains, and the Organ Mountains with the Jornada Basin below.
The Jornada (pronounced hoor-nah-duh) Basin is a closed system. All the precipitation that falls into the basin stays in the basin.
Geologic events spanning 280 million years produced the Jornada Basin. The first event was the deposition of sediments on the floor of a shallow ocean that covered the continent until about 70 million years ago. The resulting sedimentary rocks (sandstone, limestone) were then deformed, tilted, and uplifted to form hills that were the precursors to the Doña Ana and San Andres Mountains.
The mountain-building events ended about 33 million years ago. Since that time, erosive forces of water and wind have worn down the lofty mountains, forming the much lower skyline visible today. The rocks eroded from the mountains were deposited in the valley, essentially burying the base of the mountains in their own debris. The deposits in the basin are more than 5,000 feet thick.
The Desert Discovery Trail you have just enjoyed via this virtual tour is yet another project made possible through the dedication of hundreds of Asombro Institute for Science Ecucation's volunteers. We are especially grateful to the Asombro Institute's Site Development Committee chair Justin Van Zee, whose vision, sweat and hard work made the trail, into a reality. We also thank scientists Arlene Tugel and Walt Whitford for their assistance in writing the Self-guided Tour Booklet upon which this virtual tour is based. Finally, we thank the dozens of other volunteers who created and help maintain the Chihuahuan Desert Nature Park for all to enjoy.
While this virtual tour can not replace the experience of being immersed in the desert, we hope it gave you some insight about the wonders of this ecosystem.