Physiographic features

The Gravelly Ecological Site is positioned across alluvial fans, stream terraces, and fan piedmonts within LRU 42.8. Elevation ranges from 3500 to 5500 feet. Soil depth is deep to very deep (>100 cm).Slopes range from 1 to 25 percent but are normally less than 15 percent. Aspect plays a minor role on this site.

The Gravelly Ecological Site is made up of gravelly alluvium that is derived from limestone parent material. The Site is most closely associated with the Shallow, Limestone Hills, and Draw Ecological Sites. The Shallow Ecological Site occurs on associated areas where a root restricting petrocalcic horizon is less than one meter deep. The Draw Ecological site is situated in an active floodplain that sits below an old gravelly terrace or fan remnant which is occupied by the Gravelly Ecological site.

Ecological Site Key for LRU 42.8 and 42.9, Northeastern Chihuahuan Hills and Mountains

1. Site is within LRU 42.8, which is within the ustic-aridic soil moisture regime, and the thermic soil temperature regime (often contains red berry juniper).
2. Soils are loamy and not skeletal, and reside in low areas that are stream terraces and fan remnants. - Loamy Terrace ESD
2. Soils are skeletal (Greater than 35% by volume rock fragments greater than 2mm)
3. Soils are deep to very deep (greater than 100 cm to root restrictive layer).
4. Site exists in an active floodplain.-Draw ESD
4. Site exists on a stream terrace or alluvial fan-Gravelly ESD
4. Site exists on steep slopes on limestone colluvium over gypsum residuum.-Limy Gyp
Escarpment
3. Soils are very shallow to moderately deep (5-100 cm).
5. Root restrictive layer is a petrocalcic horizon.-Shallow ESD
5. Root restrictive layer is bedrock.
6. Slopes are less than 25%-Very Shallow ESD
6. Slopes are greater than 25%- Limestone Hills ESD
1. Site is located within LRU 42.9, which is in the aridic-ustic soil moisture regime and the mesic soil temperature regime (often contains alligator juniper and/or pinon pine).
7. Slopes are less than 25%- Shallow Limestone ESD
7. Slopes are greater than 25%- Limestone Mountains ESD

Glossary:

Colluvium: “Unconsolidated, unsorted earth material being transported or deposited on side slopes and/or at the base of slopes by mass movement (e.g. direct gravitational action) and by local, concentrated runoff” (Schoenberger, et al., 2012).

Petrocalcic Horizon: The petrocalcic horizon is an illuvial horizon in which secondary calcium carbonate or other carbonates have accumulated to the extent that the horizon is cemented or indurated (Keys to Soil Taxonomy, 2010).

Residuum: “Unconsolidated, weathered, or partly weathered mineral material that accumulates by disintegration of bedrock in place” (Schoenberger, et al., 2012).

Soil moisture regime: Refers to the presence or absence either of ground water or of water held at a tension of less than 1500 kPa in the soil or in specific horizons during periods of the year. Water held at a tension of 1500 kPa or more is not available to keep most mesophytic plants alive. Major differences in soil moisture are often reflected in different vegetative communities. The two major soil moisture regimes for the Guadalupe Mountains are Aridic and Ustic (Keys to Soil Taxonomy, 2010).

Soil Temperature Regime: This is the range of temperatures experienced by a soil at a depth of 50 cm. When the average temperature of a soil falls between 46 degrees F and 59 degrees, it falls into the mesic soil temperature regime. The thermic soil temperature regime falls between 59 degrees F and 72 degrees (Keys to Soil Taxonomy, 2010).

Table 2. Representative physiographic features

Climatic features

The mean annual precipitation is 10.4 inches to 18.3 inches, occurring mostly as high intensity, short-duration afternoon thunderstorms from July through September. Mean annual air temperature is 55 to 70 degrees F, and the frost-free season is 207 to 243 days.

Annual weather patterns, influenced by global climate events, such as El Nino and La Nina, affect and alter production and composition across the Gravelly Ecological Site. In general, because precipitation is minimal through the winter but increases during the summer, warm-season (C4) plants dominate the landscape. However, from year to year the production and composition can greatly shift due to variable weather patterns. The years that produce the most species richness and production are those that get slow, steady moisture through the months of May, June, and July. Late summer thunderstorms may induce heavy runoff on this site, creating flash-flooding in the draws, drainages, and canyons below.

The climate trend of the area is one toward warmer temperatures and lower precipitation. According to the Carlsbad Caverns Climate Station, during the years 2001-2011, five years received less than 10 inches of rain. Three of those years, (2003, 2005, and 2011) were below 5 inches of rain. And 2011 was both the lowest rainfall and hottest year on record. Similarly, in 1947-1957, 6 out of 11 years were below the mean low of 10.4 inches. But in that stretch, only one year, 1951, was below 5 inches. To put this in perspective, in the dry 1930’s only 2 years were below the mean low of 10.4 and none were below 5 inches. The 2001-2011 decade has been much warmer and drier than any in recorded history. In addition, during the two years of 2010 and 2011, Carlsbad Caverns National Park experienced extreme events of drought, wildfire, and flash flooding which have led to shifts in plant communities.

Table 3. Representative climatic features

Influencing water features

The Gravelly Ecological Site is not associated with a wetland or riparian system; it is an upland ecological site.

Soil features

The Gravelly Ecological Site is tied to the Bascal component of map units CC7, DR1, CC8, KB1, and KB2 within LRU 42.8, Northeastern Chihuahuan Desert Hills. The CC8 and KB2 map units are almost identical and consists of complexes of soil components which are dominated by about 50 percent Kimrose (the Kimrose component is associated with the Shallow Ecological Site) and 40 percent Bascal (Gravelly Ecological Site). The CC7 and DR1 map units are associated with 40 % Dunaway, 30% River wash, and 25% Bascal. Map unit CC7 is associated with stream systems, and CC8 is associated with alluvial fans. The complex between the Gravelly and Shallow Ecological Sites (Bascal and Kimrose components) in map unit CC8 is based on the undulating depth of the petrocalcic horizon.

The Bascal component is formed from deep gravelly alluvium derived from limestone and dolomite parent material.

In normal years this soil is driest during the winter. It is moist in the upper part for over 90 cumulative days, but fewer than 90 consecutive days during the growing season. The soil moisture regime is aridic bordering on ustic. The mean annual soil temperature: is 59 to 66 degrees F, which is classified as the thermic temperature regime.

The Bascal component is well drained, formed in gravelly fan alluvium and occurs on low to moderately sloping dissected alluvial fan remnants and stream terraces. The Bascal taxonomic class is: Loamy-skeletal, carbonatic, thermic Ustic Haplocalcids. The Bascal component has about 1.65-3.3 % organic matter in the “A horizon” which means that it probably formed under grassland conditions. Effervescence is strong.

TYPICAL PEDON: Bascal gravelly loam, on an east-facing, 7 percent slope in rangeland at an elevation of 1,380 m (4,527 ft). (Colors are for dry soil unless otherwise noted).

TYPE LOCATION: Eddy County, New Mexico; from the parking area for Yucca Canyon trailhead in Carlsbad Caverns National Park, 100 yards east, down slope. (Grapevine Draw NM USGS topographic quadrangle: UTM coordinates, NAD 83 datum, 13 N. 539068N 3551272W.

A--0 to 9 cm, (0.0 to 3.5 inches); dark grayish brown (10YR 4/2) very gravelly loam, very dark brown (10YR 2/2), moist; 45 percent sand; 20 percent clay; weak medium subangular blocky parts to moderate coarse granular structure; slightly hard, friable, , slightly sticky, slightly plastic; many very fine roots and common fine roots; common very fine interstitial and common fine interstitial pores; 1 percent nonflat subrounded indurated 600 to 1200 millimeter limestone fragments and 5 percent nonflat subrounded indurated 250 to 600 millimeter limestone fragments and 10 percent nonflat subrounded indurated 75 to 250 millimeter limestone fragments and 25 percent nonflat rounded indurated 2 to 75 millimeter limestone fragments; strong effervescence, by HCl, 1 normal; slightly alkaline, pH 7.6 by pH meter; clear smooth boundary.

Bk1--9 to 37 cm, (3.5 to 14.6 inches); dark grayish brown (10YR 4/2) gravelly loam, very dark grayish brown (10YR 3/2), moist; 35 percent sand; 22 percent clay; weak medium subangular blocky parts to moderate fine subangular blocky structure; slightly hard, friable, , slightly sticky, slightly plastic; common very fine roots and few medium roots and common fine roots; common very fine interstitial and few fine interstitial pores; 2 percent fine prominent irregular weakly cemented carbonate nodules on bottom of rock fragments and 3 percent fine prominent irregular carbonate masses on faces of peds; 3 percent nonflat subrounded indurated 75 to 250 millimeter limestone fragments and 25 percent nonflat rounded indurated 2 to 75 millimeter limestone fragments of which 15 percent are 2 to 20 millimeters; strong effervescence, by HCl, 1 normal; moderately alkaline, pH 7.9 by pH meter; clear wavy boundary.

Bk2--37 to 59 cm, (14.6 to 23.2 inches); brown (10YR 4/3) extremely cobbly loam, dark brown (10YR 3/3), moist; 35 percent sand; 24 percent clay; weak medium subangular blocky parts to moderate fine subangular blocky structure; slightly hard, friable, , moderately sticky, moderately plastic; common very fine roots and few medium roots and few fine roots; many very fine interstitial and common fine interstitial pores; 3 percent fine prominent irregular weakly cemented carbonate nodules on bottom of rock fragments and 5 percent fine prominent irregular carbonate masses throughout; 10 percent nonflat subrounded indurated 250 to 600 millimeter limestone fragments and 25 percent nonflat subrounded indurated 75 to 250 millimeter limestone fragments and 30 percent nonflat rounded indurated 2 to 75 millimeter limestone fragments of which 18 percent are 2 to 20 millimeters; violent effervescence, by HCl, 1 normal; moderately alkaline, pH 7.9 by pH meter; gradual wavy boundary.

Bk3--59 to 200 cm, (23.2 to 78.7 inches); brown (10YR 5/3) extremely stony sandy clay loam, dark yellowish brown (10YR 4/4), moist; 65 percent sand; 22 percent clay; weak fine subangular blocky structure; slightly hard, friable, , slightly sticky, slightly plastic; common very fine roots and few medium roots and few fine roots; common fine interstitial pores; 10 percent fine prominent irregular carbonate masses throughout and 5 percent medium prominent irregular weakly cemented carbonate nodules on bottom of rock fragments; 10 percent nonflat subrounded indurated 250 to 600 millimeter limestone fragments and 25 percent nonflat subrounded indurated 75 to 250 millimeter limestone fragments and 40 percent nonflat rounded indurated 2 to 75 millimeter limestone fragments of which 24 percent are 2 to 20 millimeters; violent effervescence, by HCl, 1 normal; moderately alkaline, pH 7.9 by pH meter;

Typical Surface Fragments <=3" (% Cover): 25-35%

Typical Surface Fragments > 3" (% Cover): 25-35%

Typical Subsurface Fragments <=3" (% Volume): 30-50%

Typical Subsurface Fragments > 3" (%% Volume): 30-50%

Calcium Carbonate Equivalent (percent):
A horizon-2 to 25
Bk1 horizon-20 to 52
Bk2 horizon-30 to 70

Total Average Available Water Capacity (cm H2O/cm soil): 4.43 cm

Table 4. Representative soil features

Animal community

Part I: Wildlife

The Gravelly ecological site lies at the northern extent of the Chihuahuan Desert and provides habitat for many different wildlife species.

Species of Special Interest:

These are species of special interest that have habitat needs associated with the Gravelly Ecological Site.

Rock Rattlesnake: In New Mexico, the rattlesnake is limited to the southern Guadalupe Mountains and exists within all canyons throughout the Guadalupe Ridge. It is the most frequently encountered rattlesnake in CCNP and is found around exposed bedrock where it feeds on lizards, snakes, and small mammals (SWCA Environmental Consultants, 2007).

Texas Horned Lizard: Texas horned lizards have habitat needs that require healthy harvester ant communities. Harvester ants are the preferred food of horned lizards and when this food resource declines due to shifts to a degraded plant community, or through infrastructure development, lizard numbers will also decline (Henke & Fair, 1998). Feeding may occur at nest entrances or on ant foraging trails and mature lizards are capable of eating 70 to 100 ants per day. Although ants comprise a majority of the diet, Texas horned lizards are opportunistic predators and will consume crickets, grasshoppers, beetles, centipedes, bees and caterpillars. The diagnostic plant community phase (1.1) is best for providing a wide range of plant and insect species needed for Texas horned lizard habit.

Gray Vireo: The gray vireo is found in the desert Southwest. Over 80 percent of the Gray Vireo territories in New Mexico are found in 12 sites, with the largest site being found in the Guadalupe Mountains (Pierce, 2007). The Gray Vireo appears to not winter in New Mexico but move down to the Big Bend area where it is associated with various shrubs and cacti. Summer habitat in the Guadalupe’s seems to be linked to juniper and oak plant communities. During breeding season, (April-July) the Gray Vireo are insectivorous, taking grasshoppers, stinkbugs, crickets, moths, and caterpillars for food. In New Mexico, nests are primarily in Juniper trees (Pierce, 2007). Plant communities within the historic range of variability are important for the Gray Vireo to find nesting, breeding, and brood-rearing cover. The birds will find nesting cover in plant communities 1.1 and 1.2, while moving to community phase 1.3 to find food.

Peregrine Falcon: The Peregrine Falcon is a species of concern that occurs throughout the west. According to experts at the “Living Desert Zoo and Gardens State park” in Carlsbad New Mexico, the peregrine falcon has only been spotted on a rare occasion in the fall or winter.

Common hog-nosed skunk:Hog-nosed skunks are distinguished from striped skunks primarily by the pelage, with a characteristic broad white marking beginning at the top of the head and extending down the back and tail. They make their dens in rocky areas, but probably utilize the Gravelly Ecological Site for hunting. They are omnivorous, and they eat differently according to the season. They mainly eat insects and grubs but also eat fruit, small mammals, snakes and carrion. Because rattlesnakes react to skunk musk with alarm, it is believed that skunks may feed extensively on rattlesnakes. In search of food, this skunk can turn over large areas of earth with its bare nose and front claws as it searches for food (Buie, 2003).

Mountain Lion: The mountain lion is an excellent stalk-and-ambush predator, pursuing a wide variety prey. Deer make up its primary food source, but they will also hunt species as small as insects and rodents. The mountain lion stalks through shrubs and across ledges before delivering a powerful leap onto the back of its prey with a suffocating neck bite. The mountain lion is capable of breaking the neck of its prey with a strong bite and momentum bearing the animal to the ground. Kills are generally estimated at around one large ungulate every two weeks. This period shrinks for females raising young, and may be as short as one kill every three days when cubs are nearly mature at around 15 months.

Only females are involved in parenting. Females are fiercely protective of their cubs, and have been seen to successfully fight off animals as large as black bears in their defense. Caves and other alcoves that offer protection are used as litter dens (Cougar, 2013).

The Very Shallow and Limestone Hills ecological sites provide the best habitat for the mountain lion life cycle. ON the Gravelly site, plant community 1.2 would be best for lions to hide and stalk prey. Mountain lions can work the edge of hill summits and position themselves above prey where they can pounce with a killing blow.


Eastern White-throated Wood Rat: This large rat is often called a packrat because of the large nest of sticks and other material that it incorporates into nests. The nocturnal rat feeds on a wide variety of plants and finds shelter around dense stands of cacti such as cholla and prickly pear. Plant communities 1.1 and 1.2 are ideal for nesting white-throated wood rats.

Other species associated with the Gravelly ecological site:

Birds:
Turkey Vulture
Mississippi Kite
Red-tailed Hawk
American Kestrel
Great Horned Owl
Spotted Towhee
Canyon Towhee
Cassin’s Sparrow
Brewer’s Sparrow
Black-throated Sparrow
White-crowned Sparrow
Dark-eyed Junco
Scaled Quail
White-winged Dove
Mourning Dove
Eurasian Collared Dove (introduced)
Lesser Nighthawk
Common Nighthawk
Black-chinned Hummingbird
Ladder-backed Woodpecker
Western Kingbird
Cliff Swallow
Barn Swallow
Verdin
Cactus Wren
Rock Wren
Northern Mockingbird
Curved-billed Thrasher
House Finch
House Sparrow

Mammals:
Mexican Ground Squirrel
Yellow-faced Pocket Gopher
Merriam’s Kangaroo Rat
Merriam’s Pocket Mouse
Western Harvest Mouse
Southern Plains Woodrat
Cactus Mouse
White-footed Mouse
White-ankled Mouse
Hispid Cotton Rat
North American Porcupine
Black-tailed Jackrabbit
Desert Cottontail
American Badger
Striped Skunk
Grey Fox
Coyote
Bobcat
Mule Deer
Elk
Ringtail

Reptiles:
Green Toad
Red-spotted toad
Rio-Grande Leopard Frog
Eastern Collared Lizard
Greater Earless Lizard
Round Tailed Horned Lizard
Crevice Spiny Lizard
Prairie Lizard
Common Side-blotched Lizard
Texas Banded Gecko
Chihuahuan Spotted Whiptail
Common Checkered Whiptail
Ring-necked Snake
Striped Whip Snake
Western Ground Snake

Note: This species list was composed with help from the Living Desert Zoo and Gardens State Park, Carlsbad, New Mexico.

Part II Livestock:

The Gravelly Ecological Site has traditionally been grazed by all kinds and classes of livestock, during all seasons of the year. In the early part of the 20th century, goats and sheep were used extensively along the Guadalupe Ridge, taking advantage of browse species. Currently, though, there are very few goat and sheep operations in the area due to many market factors. Cattle numbers are down as well due to drought and extensive wildfire from 2001-2011.

With a planned livestock grazing system, the Gravelly Ecological Site could be managed for sustained agriculture while maintaining the historic range of variability. Also, prescribed fire may be a part of the management mix to move the system to community phase 1.3, which is primarily a grassland plant community. The loss of goat production probably plays a role in the overall increase in shrub cover, especially in nitrogen fixing shrubs.

Hydrological functions

The Bascal soil component is in hydrologic group B. This soil has a moderate infiltration rate when thoroughly wet. It consists chiefly of deep, well drained soils that have moderately fine texture to moderately coarse texture.

Plant diversity is important on this site, as various types of root systems help sustain plant communities through drought. Deep rooted shrubs take advantage of water and nutrients deep in the profile. Fibrous and tap root systems take advantage of moisture and nutrients in the top meter of the soil.

Recreational uses

The Gravelly ecological site provides limited recreational use due to its lack of drinking water. Hiking is limited to day trips and should not be attempted without adequate water and a large hat. Hunting can be good on this site as elk and deer can be hunted where permitted.

Other information

Inventory data references

Data was collected during the years of 2011 and 2012. For all tier one data points, ocular methods were used to collect estimates of production, ground cover, and canopy cover. The Doman-Krajina method was used for canopy cover estimates. Soil pits were dug for verification on many tier one plots. Tier two and three protocols always were verified and analyzed with soil pits. Other methods used were line-point-intercept (LPI), double-sampling (DS), canopy gap (CG), and soil stability (SS). This ecological site had a number of tier one and tier two plots, with one tier three at the diagnostic plant community. Historic data from BLM monitoring points were used as well.

Type locality

Other references

Coauthors:

Aaron Miller-MLRA 70 Project Leader, NRCS
Logan Peterson-MLRA 70 Soil Scientist, NRCS

Special Contributors:

Steve Daly-Soil/Range Conservationist, Carlsbad Field Office, BLM
Herman Garcia-Ecological Site Inventory Specialist, Southwest Region 8, NRCS
Tracy Hughes-Range Conservation Technician, Carlsbad Field Office, NRCS
Darren James-Researcher, USDA, Jornada ARS

Reviewers:

Steve Daly-Soil Conservationist, Carlsbad Field Office, BLM
Herman Garcia-Ecological Site Inventory Specialist, Southwest Region 8, NRCS
Mark Moseley-Ecological Site Inventory Specialist, Texas Region 9, NRCS
Richard Strait-State Soil Scientist, New Mexico NRCS
John Tunberg-State Rangeland Management Specialist, New Mexico NRCS
Renee West-Biologist, Carlsbad Caverns National Park

ESD Workgroup:

Lu Burger-Natural Resource Specialist, State Office, BLM
Steve Daly-Soil Conservationist, Carlsbad Field Office, BLM
Samuel Denman-Cultural Resource Specialist, Carlsbad Caverns National Park
Garth Grizzle, District Conservationist, Area Range Conservationist, NRCS, retired
Charles Hibner-MLRA 70 SS Leader, NRCS, retired
Tracy Hughes-Range Conservation Technician, Carlsbad, NRCS
Laurie Kincaid-Rancher, Carlsbad
Michael McGee- Hydrologist, Roswell Field Office, BLM
Aaron Miller-MLRA 70 Project Leader, NRCS
Susan Norman-GIS Specialist, Carlsbad Caverns National Park
Logan Peterson-MLRA 70 Soil Scientist, NRCS
Mark Sando-Rangeland Management Specialist, Guadalupe District, USFS
Kent Schwartzkopf-Chief, Stewardship and Science Div., Carlsbad Caverns National Park
Renee West-Biologist, Carlsbad Caverns National Park
Pete Biggam-Soils Program Manager, National Park Service, Lakewood Colorado



References:

Ahlstrand, G., 1981. Ecology of fire in the Guadalupe Mountains and adjacent Chihuahuan Desert. Carlsbad(New Mexico): Carlsbad Caverns and Guadalupe Mountains National Park.

Bestelmeyer, et al., 2010. Practical Guidance for Developing State-and-Transition Models. Rangelands, p. 26.

Buie, L., 2003. Hog-nosed skunk. [Online]
Available at: http://itech.pensacolastate.edu/sctag/hn_skunk/index.htm
[Accessed 26 10 2012].

Burger, P., 2007. Walking Guide to the Geology of Carlsbad Cavern. Carlsbad, NM: Carlsbad Caverns and Guadalupe Mountains Association.

Burkett, B., Version 1.1. A Field Guide to Pedoderm and Pattern Classes, Las Cruces, New Mexico: USDA-ARS Jornada Experimental Range.

Cleland, D. T. et al., 2007. Ecological Subregions: Sections and Subsections of the Conterminiuos United States.. s.l.:United States Forest Service.

Cougar. (2013, September 8). In Wikipedia, The Free Encyclopedia. Retrieved 21:37, September 19, 2013, from http://http://en.wikipedia.org/w/index.php?title=Cougar&oldid=571991990
Duniway, Bestelmeyer, Tugel, 2
010. Soil Processes and Properties That Distinguish Ecological Sites and States. Rangelands, pp. 9-15.

Gebow, B. S., 2001. Search, Compile, and Analyze Fire Literature and Research Associated with Chihuahuan Desert Uplands, Tuscon: The University of Arizona.

Goldstein and Rominger, 2003. Plan for the Recovery of Desert Bighorn Sheep in New Mexico, Santa Fe: New MExico Department of Game and Fish.

Griffith, et al., 2006. Ecoregions of New Mixico. Reston(Virginia): U.S. Geological Survey.

Henke and Fair, 1998. Management of Texas Horned Lizards, Kingsville, Tx.: Caesar Kleberg WIldlife Research Institute.

Herrick, Whiteford, De Soyza, Van Zee, Havstad, Seybokd, Walton, 2001. Soil aggregate stability kit for field-based soil quality and rangeland health evalutations.. s.l.:s.n.

Kayser, D. W., 2010. Prehistory: SHort and Seet. "Different peoples over a long period of time vistied, used the abundant resoruces or lived here at CASVE.", s.l.: s.n.

Kelley, V., 1971. Geology of the Pecos Country, Southeastern New Mexico. s.l.:New Mexico bureau of Mines and Mineral Resources.

Keys to Soil Taxonomy; United States Department of Agriculture, Natural Resources Conservation District; Eleventh Edition; 2010

New Mexico Game and Fish, n.d. Wildlife Notes-Ringtail, s.l.: New Mexico Game and Fish.

Pellant, Pyke, Shaver & Herrick, 2005. Interpreting Indicators of Rangeland Health. Version 4 ed. Denver(CO.): United States Department of the Interior, Bureau of Land Managment, National science and Technology Center, Division of Science Integration.

Peterson, F. F., 1981. Landforms of the Basin and Range Province, Reno: Nevada Agricultural Experiment Station.

Pierce, L. J., 2007. Gray Vireo (Vireo vicinior) Recovery Plan, Santa Fe, NM: New Mexico Department of Game and Fish.

Schoeneberger, P.J., and Wysocki, D.A. 2012. Geomorphic Description System, Version 4.2. Natural Resources Conservation Service, National Soil Survey Center, Lincoln, NE.
Spomer, Hoback, Golick, Higley, 2006. Biology, Lifecycle, and Behavior. [Online]
Available at: http://drshigley.com/lgh/netigers/index.htm
[Accessed 26 10 2012].

SWCA Environmental Consultants, 2007. Carlsbad Caverns National Park, Environmental Assessment, s.l.: U.S. Department of Interior.

United States Department of Agriculture, Natural Resources Conservation Service, 2006. Land Resource Regions and Major Land Resource Areas of the United States, the caribbean, and the Pacific Basin. s.l.:s.n.

Contributors

Scott Woodall