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22-461: The climate is temperate and subtropical, semi-arid to subhumid, with summer rains. Average annual temperature 12-16 °C, and annual total precipitation is 400–800 mm. The Trans-Mexican Volcanic Belt pine-oak forests ecoregion covers the mountains surrounding the basin to the west, north, and east. The mountains to the north and west, including the Cofre de Perote volcano, leave the valley in

44-767: A rain shadow , and the xeric shrublands of the Tehuacán Valley matorral ecoregion occupies the center of the basin, and extend south into the Tehuacán and Cuicatlán valleys. Vegetation includes pine-oak forests and pine-fir forests at higher elevations, with dry scrub pine forests, oak forests, juniper scrub, yucca scrub, halophytic vegetation, and grassland. It includes the Llanos de San Juan and Llanos de San Andres. The basin contains several shallow, mostly alkaline lakes . Two ephemeral playa lakes, Totolcinco (El Carmen or Totolcingo) and Tepeyahualco (El Salado), lie in

66-465: A similar morphology. In its current circumscription , Nitzschia is paraphyletic . Nitzschia is found mostly in colder waters, and is associated with both Arctic and Antarctic polar sea ice , where it is often found to be the dominant diatom. Nitzschia includes several species of diatoms known to produce the neurotoxin known as domoic acid, a toxin responsible for the human illness called amnesic shellfish poisoning . The species N. frigida

88-558: Is a subtropical coniferous forest ecoregion of the Trans-Mexican Volcanic Belt of central Mexico . The Trans-Mexican Volcanic Belt pine–oak forests occupy an area of 92,503 square kilometers (35,716 sq mi), extending from Jalisco state in the west to Veracruz in the east. The main mass of the volcanic belt extends east to west through the states of Jalisco, Michoacán , México , Morelos , Tlaxcala , Puebla , and Veracruz. The ecoregion includes

110-640: Is found in the Manantlán and Cacoma sierras of Jalisco and near Morelia in Michoacán. Acer binzayedii is known only from the Sierra de Manantlán. Pinus jaliscana is also endemic to western Jalisco, where it is found mostly in the Sierra el Cuale and Sierra el Tuito. The Transvolcanic jay , ( Aphelocoma ultramarina ), Sierra Madre sparrow ( Xenospiza baileyi ) and the green-striped brushfinch ( Atlapetes virenticeps ) are near-endemic species, limited to

132-592: Is found to grow exponentially even at temperatures between −4 and −6 °C. Some Nitzschia species are also extremophiles by dint of tolerance to high salinity ; for example, some halophilic species of Nitzschia are found in the Makgadikgadi Pans in Botswana . The genus Nitzschia includes more than 1280 species and variants — for more information, see: "Genus: Nizschia " . algaebase.org . Some of these are: This diatom article

154-621: Is the largest of the maar lakes of the Oriental Basin, and lies at an elevation of 2320 meters. It is Mexico's deepest natural lake, with a maximum depth of 64 meters, and a mean depth of 38.6 meters. The lake has an area of 1.81 square kilometers. It is both saline and alkaline (pH 8.7-9.2). Lake Alchichica is ecologically unique, with stromatolite deposits and a high degree of endemism. The biota has adapted to extreme conditions characterized by high ionic concentrations of water and poor nutrient content. The dominant stromatolite species are

176-791: The Balsas dry forests to the south in the basin of the Balsas River , and the Bajío dry forests to the northwest in the basin of the Río Grande de Santiago and the lower Rio Lerma . The Central Mexican matorral lies to the north of the range in the high basins of the Plateau, including the Valley of Mexico and the upper reaches of the Lerma around Toluca . The Tehuacán Valley matorral lies in

198-523: The Mexican volcano mouse ( Neotomodon alstoni ) are endemic to the ecoregion. The Volcanic Belt pine–oak forests of eastern Michoacán and western México states is the winter habitat of monarch butterflies ( Danaus plexippus ), which migrate from temperate regions of North America east of the Rocky Mountains . The Mariposa Monarca Biosphere Reserve is within this habitat . 17.85% of

220-963: The rain shadow valley to the southeast in Puebla and Tlaxcala states. To the east, the moist Veracruz montane forests and Oaxacan montane forests are the transition between the pine–oak forests and the lowland tropical forests along the Gulf of Mexico . Pockets of montane grassland and shrubland can be found among the pine–oak forests, and constitute a separate ecoregion, the Zacatonal . The chief plant communities are pine forests, pine–oak forests, oak forests, pine–cedar forests, and pine–fir forests. The plant communities vary with elevation and rainfall. Pine forests are generally found between 2,275 and 2,600 m. Pine–oak forests occur between 2,470 and 2,600 m. Pine–cedar forests can be found above 2,700 m. Pine–fir forests occur above 3000 m. In

242-492: The Oriental Basin are home to a closely knit set of endemic species, one at each crater lake. Some of these include the Atherinopsid fishes Alchichica silverside (Poblana alchichica) , La Preciosa silverside (P. letholepis) , Chignahuapan silverside (P. ferdebueni) , and Quechulac silverside (P. squamata) . Three species of dace ( Evarra bustamantei , E. eigenmanni , and E. tlahuacensis ) formerly native to

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264-651: The basin are presumed extinct since about 1970. The WWF - Nature Conservancy system of freshwater ecoregions includes the Oriental Basin with the Valley of Mexico, Lerma River, and Lake Chapala in their Lerma-Chapala freshwater ecoregion, based on faunal similarities, especially among the Atherinopsids. Lake Alchichica ( 19°25′N 97°24′W  /  19.417°N 97.400°W  / 19.417; -97.400 ) in Tepeyahualco (municipality) , Puebla ,

286-495: The basin include El Carmen Tequexquitla, Tlaxcala ; Perote, Veracruz ; and Oriental, Puebla . Groundwater levels in the basin have been dropping in recent years because of over-exploitation for irrigation and destruction of natural recharging areas. In addition, the government is considering pumping freshwater from the Oriental basin to Mexico City to the west and Puebla to the south. The maar lakes, or axalpazcos , of

308-437: The ecoregion is in protected areas. Protected areas include: [REDACTED] Media related to Trans-Mexican Volcanic Belt pine–oak forests at Wikimedia Commons Nitzchia See text Nitzschia is a common pennate marine diatom . In the scientific literature, this genus, named after Christian Ludwig Nitzsch , is sometimes referred to incorrectly as Nitzchia , and it has many species described, which all have

330-471: The ecoregion, in western Jalisco and Colima states, is home to several endemic species. Quercus iltisii is found in the mountains of Jalisco and Colima. Quercus cualensis is known only from the Sierra el Cuale in western Jalisco between 1,800 and 2,300 meters elevation, and is endangered. Quercus tuitensis is found only in the lower montane forests of Jalisco's Sierra el Tuito. Magnolia iltisiana

352-508: The lowest part of the basin (2300 meters elevation), and remain dry for most of the year. The basin includes six maar lakes, locally called axalpazcos , lying in shallow volcanic craters and sustained by underground water. A northern group of lakes – Alchichica, Quechulac, Atexcac, and La Preciosa – lie southeast of Lake Tepeyahualco, and the southern lakes, Aljojuca and San Miguel Tecuitlapa, lie southeast of Lake Totolcinco. The basin also has five dry maars, called xalapazcos . Chief towns in

374-405: The pine forests, Montezuma pine ( Pinus montezumae ) is generally predominant, with smooth-bark Mexican pine ( P. pseudostrobus ) predominant in more humid areas, and Hartweg's pine ( P. hartwegii ) and P. tecote in dry areas with shallow soils. Pine–fir forests are composed almost entirely of Hartweg's pine ( Pinus hartwegii ) and sacred fir ( Abies religiosa ). The western portion of

396-567: The pine–oak forests of the Transvolcanic Range and the southern Sierra Madre Occidental . Other native birds include the great horned owl ( Bubo virginianus ), long-tailed wood partridge ( Dendrortyx macroura ), white-tipped dove ( Leptotila verreauxi ), Montezuma quail ( Cyrtonyx montezumae ), banded quail ( Philortx fasciatus ), northern bobwhite ( Colinus virginianus ), and grey-barred wren ( Campylorhynchus megalopterus ). The volcano rabbit ( Romerolagus diazi ) and

418-693: The smaller mountain ranges which rise from the Mexican Plateau, including the Sierra de Santa Rosa , Sierra de Lobos , and Sierra de Pénjamo in Guanajuato, and northwards to El Gogorrón National Park in San Luis Potosí . The pine–oak forests are surrounded by tropical dry forests at lower elevations to the west, northwest, and south; the Jalisco dry forests to the west and southwest;

440-585: The spongy type Enthophysalis atrata , Enthophysalis sp. Calothrix cf. Parletina and Calothrix sp. and the columnar stromatolites Enthophysalis lithophyla and Nitzchia sp. In the deep parts of the lake, abundant cladophores develop on the spongy stromatolites, with many cyanobacterial epiphytes Chamaesiphon halophilus , Heteroleibleinia profunda , Mantellum rubrum and Xenococcus candelariae . 23 genera of phytoplankton have been found: fourteen genera of Chrysophyta , five of Cyanophyta and four of Chlorophyta . The dominant species throughout

462-533: The submerged rooted hydrophytes Cyperus laevigatus , Potamogeton pectinatus and Ruppia maritima , and the free-floating hydrophyte Lemna gibba . Animals endemic to Lake Alchichica include the Taylor's Salamander (Ambystoma taylori) , the fish Poblana alchichica (Alchichica silverside, Charal de Alchichica), and the isopod Caecidotea williamsi . Trans-Mexican Volcanic Belt pine-oak forests The Trans-Mexican Volcanic Belt pine–oak forests

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484-485: The year are Agmenellum sp., Amphora sp., Chaetoceros similis , Coscinodiscus sp., Cyclotella striata , Nodularia spumigena , Stephanodiscus niagarae and Synechocystis sp. The best represented species best of vascular plants in the axalpazcos are rooted emergent hydrophytes Eleocharis montevidensis , Juncus andicola , J. balticus subsp. mexicanus (syn. J. mexicanus ), Phragmites australis , Scirpus californicus and Typha domingensis ,

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