Chihuahuan Desert: Difference between revisions

SeveralThere are several larger mountain ranges includein the Chihuahan Desert, including the [[Sierra Madre Oriental|Sierra Madre]], the [[Sierra del Carmen]], the [[Organ Mountains]], the [[Franklin Mountains (Texas)|Franklin Mountains]], the [[Sacramento Mountains]], the [[Chisos Mountains]], the [[Guadalupe Mountains]], and the [[Davis Mountains]]. These create "[[sky island]]s" of cooler, wetter, [[climate]]s adjacent to, or within the desert, and such elevated areas have both coniferous and broadleaf woodlands, including forests along drainages and favored exposures. The lower elevations of the [[Sandia–Manzano Mountains]], the Magdalena–San Mateo Mountains, and the [[Gila Wilderness|Gila]] Region partly border the Chihuahuan Desert and partly border other ecoregions that are not deserts.

The desert is mainly a [[rain shadow]] desert because the two main mountain ranges covering the desert, the [[Sierra Madre Occidental]] to the west and the [[Sierra Madre Oriental]] to the east, block most moisture from the Pacific Ocean and the Gulf of Mexico, respectively.<ref name=NMSU>{{cite web | url = http://ddl.nmsu.edu/chihuahua.html | title = The Chihuahuan Desert | publisher = New Mexico State University | access-date = February 16, 2013 | url-status = dead | archive-url = https://web.archive.org/web/20121227092714/http://ddl.nmsu.edu/chihuahua.html | archive-date = December 27, 2012 }}</ref> Climatically, the desert mostly has an arid, mesothermal climate with one rainy season in the late summer and smaller amounts of precipitation in early winter, the mean daily temperature of the coldest month warmer than {{convert|0|C|F|abbr=on|}}.<ref name= NMSU /> The majority of rain falls between late June and early October, during the [[North American Monsoon]] when moist air from the Gulf of Mexico penetrates into the region, or much less frequently, when a tropical cyclone moves inland and stalls.<ref name= NMSU /><ref name= NPS1 >{{cite web | url = http://www.nps.gov/cave/naturescience/deserts.htm | title = Chihuahuan Desert| publisher = National Park Service | access-date = February 16, 2013}}</ref> Owing to its inland position and higher elevation than the [[Sonoran Desert]] to the west, mostly varying from {{convert|480| to |1800|m|0|abbr=on}} in altitude,<ref name= EOE >{{cite web | url = http://www.eoearth.org/article/Chihuahuan_desert | title = Chihuahuan Desert | publisher = Encyclopedia of Earth | access-date = February 16, 2013}}</ref> the desert has a slightly milder climate in the summer (though usually daytime June temperatures are in the range of {{convert|32|to|40|C|F|abbr=on|disp=or}}), with mild to cool winters and occasional to frequent freezes.<ref name= NPS1 /> The average annual temperature in the desert varies from about {{convert|13|to|22|C|F}}, depending on elevation and latitude. The hottest temperatures in the desert occur in lower elevation areas and valleys, including near the Rio Grande from south of El Paso into the Big Bend, and the Bolson de Mapimi.<ref name= EOE /> Northern and eastern portions have more definite winters than southern and western portions, receiving a portion of winter precipitation as snowfall most winters.<ref name= NPS1 /> The mean annual precipitation for the Chihuahuan Desert is {{convert|235|mm|in|abbr=on}} with a range of approximately {{convert|150|–|400|mm|0|abbr=on}}, although it receives more precipitation than most other warm desert ecoregions.<ref name= NMSU /> Nearly two-thirds of the arid zone stations have annual totals between {{convert|225|and|275|mm|in|abbr=on}}.<ref>[http://museum.utep.edu/chih/pdf/chihuahuanclimate.pdf Chihuahuan Climate] {{webarchive |url=https://web.archive.org/web/20060906101600/http://museum.utep.edu/chih/pdf/chihuahuanclimate.pdf |date=September 6, 2006 }}, Chihuahuan Desert Research Institute</ref> Snowfall is scant except at the higher elevation edges. The desert is fairly young, existing for only 8000 years.<ref name= NMSU />

The creosote bush (''[[Larrea tridentata]]'') is the dominant plant species on gravelly and occasional sandy soils in valley areas within the Chihuahuan Desert. The other species found with creosote bush is found with depend on factors including the soil type, elevation, and degree of slope. Viscid acacia (''[[Vachellia vernicosa]]''), and tarbush (''[[Flourensia]] [[Flourensia cernua|cernua]]'') dominate northern portions, while broom dalea (''[[Psorothamnus]] [[Psorothamnus scoparius|scoparius]]'') occurs on sandy soils in western portions. ''[[Yucca]]'' and ''[[Opuntia]]'' species are abundant on slopes and uplands in most areas, while Arizona rainbow cactus (''[[Echinocereus polyacanthus]]'') and Mexican fire-barrel cactus (''[[Ferocactus pilosus]]'') inhabit portions near the US–Mexico border.

[[Herbaceous plant]]s, such as bush muhly (''[[Muhlenbergia porteri]]''), blue grama (''[[Bouteloua gracilis]]''), gypsum grama (''[[Bouteloua breviseta|B. breviseta]]''), and hairy grama (''[[Bouteloua hirsuta|B. hirsuta]]''), are dominant in desert grasslands and near the mountain edges including the Sierra Madre Occidental. Lechuguilla (''[[Agave lechuguilla]]''), honey mesquite (''[[Prosopis glandulosa]]''), ''[[Opuntia macrocentra]]'' and ''[[Echinocereus pectinatus]]'' are the dominant species in western [[Coahuila]]. Ocotillo (''[[Fouquieria splendens]]''), lechuguilla, and ''[[Yucca filifera]]'' are the most common species in the southeastern part of the desert. Candelilla (''[[Euphorbia antisyphilitica]]''), ''[[Mimosa zygophylla]]'', ''[[Acacia glandulifera]]'' and lechuguilla are found in areas with well-draining, shallow soils. The shrubs found near the Sierra Madre Oriental are exclusively lechuguilla, guapilla (''[[Hechtia glomerata]]''), Queen Victoria's agave (''[[Agave victoriae-reginae]]''), sotol (''[[Dasylirion]]'' spp.), and barreta (''[[Helietta]] [[Helietta parvifolia|parvifolia]]''), while the well-developed [[herbaceous layer]] includes grasses, [[Fabaceae|legumes]], and cacti.

Desert or arid grasslands comprise 20% of this desert and are often mosaics of shrubs and grasses. They include purple three-awn (''[[Aristida purpurea]]''), black grama (''[[Bouteloua eriopoda]]''), and sideoats grama (''[[Bouteloua curtipendula]]''). Early Spanish explorers reported encountering grasses that were "belly high to a horse;"; most likely these were big alkali sacaton (''[[Sporobolus wrightii]]'') and tobosa (''[[Pleuraphis]] [[Pleuraphis mutica|mutica]]'') along floodplain or bottomland areas.<ref name="WWF"/>

A 2017 assessment found that {{cvt|35,905|km²|sqmi}}, or 7%, of the ecoregion is in protected areas.<ref name = dinerstein/> Protected areas include [[Buenos Aires National Wildlife Refuge]] in Arizona,; [[Janos Biosphere Reserve]], [[Médanos de Samalayuca Natural Protected Area]] and [[Cañón de Santa Elena Flora and Fauna Protection Area]] in Chihuahua,; [[Cuatro Ciénegas Basin]], [[Ocampo Flora and Fauna Protection Area]], and part of [[Maderas del Carmen|Maderas del Carmen Biosphere Reserve]] in Coahuila,; [[Mapimí Biosphere Reserve]] and [[Cañón de Fernández State Park]] in Durango,; [[Bitter Lake National Wildlife Refuge]], [[Bosque del Apache National Wildlife Refuge]], [[Carlsbad Caverns National Park]], [[Carrizozo Malpais]], [[Oliver Lee Memorial State Park]], [[Organ Mountains–Desert Peaks National Monument]], [[Petroglyph National Monument]], [[Sevilleta National Wildlife Refuge]], and [[White Sands National Park]] in New Mexico,; and [[Big Bend National Park]], [[Big Bend Ranch State Park]], Black Gap Wildlife Management Area, [[Franklin Mountains State Park]], and part of [[Guadalupe Mountains National Park]] in Texas.