Vascular Plants of Carlsbad Caverns National Park
Vascular Plants of Carlsbad Caverns National Park Taxonomy revised August 2012 Spore Plants – Lycophytes, Ferns, and Allies Lycophytes Selaginellaceae: Spike‐moss family Selaginella arizonica Arizona spike‐moss Selaginella mutica bluntleaf spike‐moss Selaginella pilifera resurrection plant Selaginella wrightii Wright’s spike‐moss Ferns and Fern Allies Aspleniaceae: Spleenwort family Asplenium resiliens blackstem spleenwort Equisetaceae: Horsetail family Equisetum laevigatum horsetail, smooth scouring‐rush Pteridaceae: Brake family Adiantum capillus‐veneris maiden‐hair fern Argyrochosma microphylla small‐leaf false cloak fern Astrolepis cochisensis Cochise cloakfern, Cochise scaly cloakfern Astrolepis integerrima hybrid cloakfern Astrolepis sinuata wavyfrond cloakfern Cheilanthes alabamensis Alabama lipfern Cheilanthes eatonii Eaton’s lipfern Cheilanthes feei Fee’s lipfern, slender lipfern Cheilanthes tomentosa woolly lipfern Cheilanthes villosa scaly lipfern, villous lipfern Pellaea atropurpurea purple cliffbrake Pellaea intermedia creeping cliffbrake Gymnosperms Cupressaceae: Cypress family Juniperus deppeana alligator juniper Juniperus monosperma one‐seed juniper Juniperus pinchotii Pinchot juniper, redberry juniper Juniperus scopulorum Rocky Mountain juniper Ephedraceae: Jointfir family Ephedra aspera boundary ephedra, rough jointfir Ephedra torreyana Torrey Mormon tea Ephedra trifurca longleaf jointfir Ephedra viridis green Mormon tea
Dry and sunny as deserts are, they are almost never without fungi. It doesn’t seem right, but we mostly hear about the forest mushrooms that grow in lush, moist, dark areas. However, they are essential parts of all ecosystems, including our desert.
First, it’s also important to realize that fungi are not plants. They do not have chlorophyll, the pigment needed for photosynthesis. Fungi cannot capture sunlight and manufacture the carbon compounds needed for living.
Second, we should note that mushrooms are really just the above-ground visible structures of many (but not all) types of fungi. They are a mechanism for dispersing the spores with which fungi reproduce and spread. The bulk of fungal activity goes on at a microscopic level, in the hyphae, which are very long structures that are a single cell wide.
One very important type of fungus is ectomycorrhizae (which means external root fungi). These fungi wrap themselves around the tiny root tips and engage in a symbiotic relationship with most plants on earthâscientists say 80 to 95 percent of plants. They take up mineral nutrients from the soil and exchange them with plants for photosynthetically fixed carbon, thereby benefiting the plants and the fungi. Mycoorhizal fungi are therefore very important, constituting a major energy flow pathway in terrestrial ecosystemsâincluding the deserts.
Of course, the park also has mushrooms. They pop up from time to time among the grasses after there has been a good wetting rain.
Marine Plants / Algae
Algae are everywhere. The most famous algae, of course, are the seaweeds and kelps. But you don’t need an ocean to have algae. There are many different kinds, some of which exist as single-celled organisms. Some of these microscopic plants live in fresh water. Some live on or in the soil [see Lichens]. You’ve probably seen them in your pets’ water dishes, even inside the house. That’s because their single-celled reproductive spores are floating around in the air all the time.
In Carlsbad Caverns National Park, most kinds of algae are single-celled. As in many semi-arid and arid desert areas, the algal spore can survive being dried out for long periods of time. Then when water is available they grow into masses that are often visible. When the park gets a good rain, the water percolates down through the various limestone layers until it gets to a less-permeable layer. Then the water travels sideways and eventually runs down the sides of cliffs. You can see this on the Walnut Canyon entrance road. And along with the water running down are populations of algae that appear to stain the rocks black.
Some of these algae live in the caves, too. Under normal light conditions, they will grow on walls or in pools as far into a cave as the sunlight penetrates (the twilight zone). In caves with artificial light sources of suitable wavelengths, such as Carlsbad Cavern, algae will grow in the dark zones near the lights. These algae are considered pest plants, and are kept under control periodically by park staff.
Among the algae that live on the soil is a blue-green alga in the genus Nostoc. This plant, from a very ancient group that was among the first plants on earth, survives the dry periods as spores. After a rain, the algal cells hydrate, begin their biological functions, and begin to photosynthesize. They also make a gelatinous sheath that connects many cells together to form visible ribbons or balls of living algae. After the area dries out again, the Nostoc ribbons and balls dry up and look like black potato chip pieces.
Carlsbad Caverns National Park has lush vegetative cover when compared to the drier deserts to the west. Woody plants predominate. Unlike Death Valley, for instance, there is almost no bare ground that can suddenly flush with annual wildflowers in an unusual rainy period. While this park’s wildflowers are not always as dramatically eye-catching, they are quite beautiful and abundant, with both annuals and perennial plants represented. The huge variety of plants and the mild climate can result in delightful flower surprises in almost any month of the yearâespecially if you look closely! The tall Torrey yuccas often put up their large white flower clusters in late winter. At the same time, the secretive desert anemones, which spend most of the year hidden underground as tubers, send up delicate flower stalks each topped with one white flower.
If the summer rains materialize (which is not guaranteed), there will be sudden appearances of many interesting flowers, such as the large blue flowers of Lindheimer’s morning glory vine and the tiny red flowers of another morning glory called scarlet creeper.
In dry years, the park’s perennial plants (including shrubs and trees) provide the most reliable flowering. In very dry years, even some of them do not flower or bear fruit.
According to its vegetation map, about a third of the park (14,586 acres) is covered in grasslands. There are many different grassland plant associations within this group, sometimes with very different species compositions and appearances. Some of the park’s grasslands have high shrub cover, as much as 25 percent.
Among the most fascinating of the park’s grasslands are those dominated by the grass called curlyleaf muhly (Muhlenbergia setifolia). According to the vegetation map report, these “give the mid-elevation slopes their distinctive character and are part of what sets the landscape of the park apart from most others in the Southwest.”
Curlyleaf muhly is a grass that occurs almost entirely in the Chihuahuan Desert, and even here it is rarely very common. The park vegetation map report noted that while similar curlyleaf muhly-dominated communities are found occasionally throughout the range, none are known to dominate their respective landscapes as those in the park do. These associations are among the newly described plant associations for the park.
The grass family is prominently represented on the park’s plant list, with 135 known species. Some of them are non-native and a few of those are invasive, damaging species, but most are native.
Trees and Shrubs
Woody plantsâtrees and shrubsâare the predominant features of much of the park’s vegetation. The park’s vegetation map documents that more than half the park is shrubland, with 17,858 acres of montane shrubland and 9,295 acres of desert shrubland. Other smaller map units include 1,753 acres of arroyo riparian woodland and shrubland, 1,765 of woodland, and 1,989 of “other,” which includes small areas of some very interesting communities, including the forested wetland at Rattlesnake Springs.
Shrubs are prominent on the park’s landscape, and even most of the tree species have shrubby growth habits. Few of the park’s trees are very tall. The tallest species (ponderosa pine, chinkapin oak, alligator juniper, and bigtooth maple) occur mostly in the western portions of the park on ridgetops and in drainages. These are in the plant groupings called montane woodlands.
In the lower-elevation eastern end of the park, Chihuahuan shrublands prevail. These include several associations anchored by Pinchot juniper (Juniperus pinchotii), as well as many others centered on such shrubs as sandpaper oak, viscid acacia, ocotillo, mariola, prickly pear cactus, creosotebush, tarbush, littleleaf sumac and mesquite.
The forested riparian wetland area at Rattlesnake Springs (with permanent water) is also home to a tall gallery of native netleaf hackberry trees, cottonwoods and willows. The intermittently flooded riparian shrublands are dominated by Apache plume, mescal bean, green sotol, catclaw acacia, and littleleaf sumac.
The park’s vegetation map and report are available at the Natural Heritage New Mexico website: http://nhnm.unm.edu/vlibrary/pubs/index.php5. Search on “Carlsbad Caverns National Park,” then click on the vegetation map entry.)
The backcountry of Carlsbad Caverns National Park has quite a few delightful surprises for tree lovers. There are the oak-madrone band cove woodlands. Perched in bands along horizontal sedimentary layers, these woodlands contain small clusters of maples, chinkapin and gray oaks, and Texas madrones. Canyon bottoms are home to the maple-oak ravine woodlands, with chinkapin oaks and bigtooth maples and sometimes alligator junipers. Chinkapin oaks are trees of the eastern United States that reach the very western limits of their range in southern New Mexico.
Southwestern chokecherry trees, nestled inconspicuously among other trees most of the year, burst into bloom in April, covering their branches with clusters of small white flowers. Their nectar and pollen are extremely popular with insects, and the tasty red fruits are quickly snapped up by all kinds of wildlife.
Shrub life is abundant and diverse in the park. Our native mulberry tree (Morus microphylla) grows only to the height of a good-sized shrub and makes a fruit so popular with wildlife that people rarely see it. Mescal bean produces large clusters of fragrant purple flowers that smell like grape drink. Algerita fills the air with sweet perfume from its small yellow flowers. Lotebush, with the exotic scientific name of Ziziphus obtusifolia, produces a quarter-inch dark blue fruit that reminds some of gumdrops. (Wildlife love to eat them, but people don’t.) Mexican buckeye is a beautiful shrubby tree that has pink flowers early in spring and hard, dry fruits that remind us of true buckeyes, to which they are not related. They are related, however, to western soapberry trees, whose fruits produce a soapy substance when they get wet. In the West, many of our cacti get quite large and we consider them shrubs.
Cacti / Desert Succulents
Ask someone to name a desert plant, and she will probably say “cactus.” The plants of the cactus family are the most commonly associated with deserts, especially in the Americas. The cactus family is almost entirely a New World family, occurring as natives in Central, South and North America.
Of all the world’s deserts, the Chihuahuan Desert maintains the highest diversity of cactus species. Even though the scientists who name cacti (called taxonomists) don’t agree on most of the names of these prickly plants, they do agree there are many different types here.
For example, everybody agrees that the Lee pincushion cactus occurs in Carlsbad Caverns National Park and the immediate vicinity and nowhere else. But this tiny plant has had a dozen names over the years, and even now it goes by at least two official scientific names: Escobaria sneedii var. leei and Coryphantha sneedii var. leei. Luckily, the plants don’t care what people call them and they go about their business in spite of our confusion.
Using the names the park has chosen to follow, its vascular plant list notes 26 species or subspecies of cacti. They range from the tiny Lee pincushion and button cacti to the large prickly pears and huge clumps of strawberry hedgehogs. Other colorfully named examples include rainbow cactus and Christmas cholla.
Flowering season and flower color vary among the park’s cacti. The tiny pincushions usually put out their pink flowers in spring. The yellow flowers of prickly pears appear in May and the stunning reds of the claret cup cacti show up in June. The purples of strawberry hedgehogs and cane chollas follow.
While cacti do store moisture in their swollen stems (the green part) and guard it with their spines (actually modified leaves), they really would not provide a good drink of water if you were thirsty. The moisture is quite thick, sticky, and tastes bad.
Cacti play a key role in providing habitat for wildlife. Their flowers provide pollen for bees, especially those called cactus bees. Their fruits feed rock squirrels, insects, and other wildlifeâand people like them too! Their stems (or pads) are popular food for deer and the caterpillars of several species of moths feed inside the pads. Finally, birds, such as the aptly named cactus wren, use cacti as a fortified place to build nests and raise young.
Other desert succulents present in the park include the agaves and yuccas. The New Mexico agave grows at the higher elevations, while the lechuguilla (Agave lechuguilla) is common in the lower elevations. Lechuguilla is considered an indicator plant of the Chihuahuan Desert, meaning that where it occurs is Chihuahuan Desert. The tree-like Torrey yuccas and low-growing banana yuccas grace the lower elevations and provide habitat for yucca moths, which pollinate their flowers as they lay their eggs.
The common shrubby junipers you see in the visitor center area of the park are an ecologically important and unusual species called Pinchot juniper (Juniperus pinchotii). Another of its common names is redberry juniper, but that name is also used for other species of juniper. The scientific name honors Gifford Pinchot, the first chief of the US Forest Service.
It wasn’t until 1969 that park staff realized that these junipers weren’t the one-seed juniper so common elsewhere in the West (Juniperus monosperma). At that time, park biologist Walter Kittams consulted with botanical experts and determined that the junipers at the park’s lower elevations are all Pinchot junipers.
Junipers are dioecious plants, meaning that they have separate trees that produce female reproductive parts (berries or cones) and male reproductive parts (the tiny cones that produce pollen). It’s not always easy to tell Pinchot from one-seed juniper if you look at male plants because they look similar. The females produce the seed cones, blue for one-seed junipers and yellow to red and reddish-brown for Pinchot junipers.
This distinction is no small matter ecologically. Most junipers, including one-seed, do not resprout from the stump after fire or cutting. But Pinchot juniper is a vigorous resprouter. Therefore, it is naturally adapted to recover from fire, a critical ecosystem component of the Chihuahuan Desert.
Pinchot junipers are shrubs or small trees, with multiple stems and heights of 3 to 20 feet. The species occurs only in southeast New Mexico and scattered locations in west-central Texas and western Oklahoma.
Among its many attractions for wildlife, Pinchot juniper is a larval host for the juniper hairstreak butterfly (Callophrys gryneus), meaning that the caterpillars eat juniper. The berries of Pinchot juniper are a valuable food source for numerous species of birds (including mockingbirds) and small mammals (ringtail, fox, raccoon). Insects are also known to feed on it.
Pinchot juniper provides valuable cover for numerous wildlife species. Many species of birds use Pinchot juniper for nesting and roosting cover, especially the gray vireo, a bird listed as threatened by the state of New Mexico.
Lichens are the result of a symbiotic relationship between algae and fungi. At Carlsbad Caverns National Park, lichens can be seen on rocks and tree trunks to a limited extent. More prominent are the black, brown, and white “crusts” that can be seen on the soil surface. These crusts are living organisms, composed of various lichens, algae, mosses, and liverworts. Previously referred to as “cryptogamic crusts,” researchers prefer to use more scientifically correct terms, such as “microphytic” (tiny plants) or “microbiotic” (tiny organisms) to describe these organisms.
The crusts don’t look very impressive when they’re dry, but when it rains they come out of dormancy quickly. Rapidly absorbing moisture, they develop the deeper pigments (especially greens) for photosynthesis. During this time, the plants take advantage of the moisture to grow and reproduce by producing spores.
Microphytic crust can be an important component of arid and semi-arid ecosystems. For example, they prevent soil erosion. This happens two ways. First, the root-like structures of lichens and mosses, along with the filaments of some algae, bind the soil particles together. This often creates an irregular soil surface that interrupts wind patterns, reducing wind erosion and trapping wind-borne soil particles. Second, the crusts physically protect the soil by covering it with their thalli (‘bodies’), thereby reducing rain-caused erosion and removal of sediment.
Crusts also improve the moisture content of soils by increasing the depth of water penetration and the total soil moisture content. Crusts may also decrease evaporation from the soil surface, enhancing the higher rain infiltration rates found in crusted soils. Crusts enhance seed germination and seedling development, presumably by providing a stable soil substrate and extra nutrients.
The effects of algae and lichens on soil fertility have been studied extensively. Certain crusts contribute high quantities of nitrogen, an extremely limited nutrient in desert soils. Crusts also contribute organic matter (carbon compounds) to soils.
These crusts tend to be rather fragile and are often severely damaged by mountain bikes, hikers, cattle and fire. Studies have documented varying recovery times, usually measured in decades. These are just some of the plants that benefit when hikers stay on trails.
Ordinarily, people don’t think of ferns when they think of deserts. Of course, most ferns in the world are distributed in wet habitats, especially in warm regions. But our area also has quite a few. They look shriveled and dead much of the time, but that’s just one of their adaptations to desert conditions. They use water-saving desert adaptations, such as small fronds (leaves) with shading hairs, scales, or waxy coverings to hold in water. When it rains, the dead-looking dry fronds turn green in a few hours and begin the process of photosynthesis.
The plants referred to as “ferns and fern allies” are plants that have vascular tissue (xylem and phloem for conducting water and sugars), but do not produce fruits and seeds. They mostly reproduce by spores or vegetative (non-sexual) reproduction. Ferns are very ancient plants that date back more than 300 million years. Their ancestors date back to the Carboniferous period when coal deposits were forming.
Carlsbad Caverns National Park has 13 known species of ferns, including maidenhair fern, cloak fern, lipfern, cliffbrake, and spleenwort. The park’s fern allies include one horsetail (also called a scouring rush) and four species of spikemosses, some of which are called “resurrection ferns.”