The Zacatonal is a montane grassland and shrubland ecoregion of central Mexico .
38-478: The Zacatonal consists of several enclaves of grassland and shrubland occupying the highest peaks of the Trans-Mexican Volcanic Belt , covering about 306 square kilometers (118 sq mi). Zacatonal is found above 3500 meters elevation on the volcanoes Popocatépetl , Iztaccihuatl , Malinche , Nevado de Toluca , Cofre de Perote , Pico de Tancítaro , and Pico de Orizaba . Zacatonal
76-559: A 70-year period, identifying overgrazing, global changes, and the ecological effects of megafauna extinction as key factors. Their findings shed light on the multifaceted drivers behind changes in savannah ecosystems. Echoing this theme of alternative strategies to combat overgrazing, Kriegisch et al. (2019) demonstrated how drift- kelp availability could reduce the foraging movement of overgrazing sea urchins, suggesting that alternative food sources may significantly influence grazing behaviors and aid in managing marine ecosystem pressures. In
114-680: A companion of the Pico de Orizaba (4,580 metres (15,030 ft)). The mountains are home to the Trans-Mexican Volcanic Belt pine-oak forests , one of the Mesoamerican pine-oak forests sub- ecoregions . The Trans-Mexican Volcanic Belt has many endemic species, including the Transvolcanic jay ( Aphelocoma ultramarina ). Volcanic ash make soils in the region very fertile, which (especially coupled with elevation making tropical climate milder) has led to high human population densities in
152-563: A complex array of what could be multiple factors affecting the deformation of the belt. It exhibits many volcanic features, not limited to large stratovolcanoes, including monogenetic volcano cones, shield volcanoes , lava dome complexes, and major calderas . Prior to the formation of the Trans-Mexican Volcanic Belt, an older, but related volcanic belt, the Sierra Madre Occidental occupied
190-459: A majority of the Trans-Mexican Volcanic Belt but smaller volumes of intraplate-like lavas, potassium rich rocks, and adakites are associated with the area. Middle Miocene adakitic (more felsic) rocks are found furthest from the trench and along the volcanic front of the central Trans-Mexican Volcanic Belt during the Pliocene - Quaternary . It has been suggested that slab melting contributed to
228-560: A now active Trans-Mexican Volcanic Belt. By the Middle Miocene, the transition from the silicic to more mafic compositions was complete, and can be considered the beginning of the Trans-Mexican Volcanic Belt. Due to the orthogonal orientation of the Trans-Mexican Volcanic Belt in relation to the trend of Mexican tectonic provinces, its Pre- Cretaceous basement is highly heterogeneous. The Trans-Mexican Volcanic Belt east of 101°W rests upon Precambrian terranes, assembled into
266-470: A similar vein, the research by Cai et al. (2020) presents a stark example of the terrestrial impact of overgrazing, showing how the fertile island effect collapses under extreme conditions in shrub-encroached grasslands . This case study emphasizes the critical need for sustainable grazing practices to protect soil health and maintain ecosystem functionality, further illustrating the wide-reaching consequences of overgrazing across diverse habitats. Overgrazing
304-581: A subspecies of Goldman's broad-clawed shrew . Many of the grasslands are in a degraded state from overgrazing by livestock or unregulated burning. In 1935 the Mexican government placed nearly 4,000 km of the mountains surrounding the Valley of Mexico under protection, including both Zacatonal and lower-elevation pine-oak forests. Trans-Mexican Volcanic Belt The Trans-Mexican Volcanic Belt ( Spanish : Eje Volcánico Transversal ), also known as
342-458: Is a massive threat to the native species of flora and fauna, especially the native bushes which are often overlooked by invasive species looking for homes. Mustalids, rabbits, hares and possums often eat the plants that hold soil together. This makes the ground very unstable and crumbly. If soil is unstable, it is prone to collapse in extreme weather events such as floods and heavy rain. This is detrimental to farmers of crops and animals alike. 40% of
380-543: Is also a distinct physiographic province of the larger Sierra Madre System physiographic division. The Sierra de Ajusco-Chichinauhtzin also forms part of the Belt. The highest point, also the highest point in Mexico, is Pico de Orizaba (5,636 metres (18,491 ft)) also known as Citlaltépetl, located at 19°01′N 97°16′W / 19.017°N 97.267°W / 19.017; -97.267 . This, and several of
418-858: Is bordered by the North American Plate (NAM) and the Caribbean Plate to the northeast, the Pacific Plate to the west, and to the south by the Nazca Plate. The Cocos and Rivera are relatively young oceanic plates (25 and 10 Ma) that are subducting along the Middle American Trench at different convergence rates (Rivera = ~30 mm/yr and the Cocos = ~ 50–90 mm/yr). Commonly found subduction related rocks such as calc-alkaline rocks volumetrically occupy
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#1732788125350456-507: Is considered the main cause of woody plant encroachment at the expenses of grasses on a land area of up to 45 million hectares. In many arid zones in Australia , overgrazing by sheep and cattle during the 19th century, as pastoralism was introduced by European settlers, caused many long-lived species of trees and shrubs to give way to short-lived annual plants and weed species. Introduced feral rabbits , cats and foxes exacerbated
494-402: Is surrounded by the Trans-Mexican Volcanic Belt pine-oak forests ecoregion at lower elevations. The climate is temperate and subhumid at lower elevations, becoming alpine and subhumid at the highest elevations. The predominant plant community is grassland, ranging from subalpine to alpine. Open forest of Hartweg's pine ( Pinus hartwegii ) and/or Montezuma pine ( Pinus montezumae ) marks
532-645: Is used as an example in the economic concept now known as the Tragedy of the Commons devised in a 1968 paper by Garrett Hardin . This cited the work of a Victorian economist who used as an example the over-grazing of common land. Hardin's example could only apply to unregulated use of land regarded as a common resource. Normally, rights of use of common land in England and Wales were, and still are, closely regulated, and available only to "commoners". If excessive use
570-591: The American bison of the Great Plains , or migratory wildebeest of the African savannas , or by holistic planned grazing. Overgrazing typically increases soil erosion . With continued overutilization of land for grazing, there is an increase in degradation. This leads to poor soil conditions that only xeric and early successional species can tolerate. A meta-analysis of 148 studies found that
608-667: The North American Plate along the northern end of the Middle America Trench formed the Trans-Mexican Volcanic Belt. The Trans-Mexican Volcanic Belt is a unique volcanic belt; it is not parallel to the Middle American Trench, and many of the main stratovolcanoes are positioned obliquely to the general position of the arc. In addition to the physiographic complexities, igneous compositions vary—dominant subduction-related products contrast with intraplate geo-chemical signatures. The many intriguing aspects of
646-569: The Pacific Ocean to the Gulf of Mexico between 18°30'N and 21°30'N, resting on the southern edge of the North American Plate . This approximately 1000 kilometer long, 90–230 km broad structure is an east–west, active, continental volcanic arc ; encompassing an area of approximately 160,000 km . Over several million years, the subduction of the Rivera and Cocos plates beneath
684-612: The Transvolcanic Belt and locally as the Sierra Nevada ( Snowy Mountain Range ), is an active volcanic belt that covers central-southern Mexico . Several of its highest peaks have snow all year long, and during clear weather, they are visible to a large percentage of those who live on the many high plateaus from which these volcanoes rise. The Trans-Mexican Volcanic Belt spans across Central-Southern Mexico from
722-575: The Mongolian steppes, Liu et al. (2013) found that approximately 60% of vegetation decline could be attributed to climate factors, with the rest significantly influenced by increased goat density due to overgrazing. This points to a complex interplay between climate change and grazing practices in ecosystem degradation. Further expanding our understanding, Stevens et al. (2016) investigated woody encroachment in South African savannahs over
760-640: The Oaxaquia microcontinent and on the Paleozoic Mixteco terrane . West of 101°W, the Trans-Mexican Volcanic Belt resides on top of the Guerro composite terrane—a make up of Jurassic to Cretaceous marine marginal arcs, which are built on Triassic –Early Jurassic siliclastic turbidites . Assemblage of these basement rocks results with a thickness of 50–55 km east of 101°W and 35–40 km west of 101°W. The subducting plates originated from
798-613: The Zacatonal is distinct from both temperate North America's alpine grasslands and the alpine páramo of Central and South America, and includes many endemic species. The Sierra Madre sparrow ( Xenospiza baileyi ) is found in the transition zone between the Zacatonal and pine forests. Native mammals include the Mexican volcano mouse ( Neotomodon alstoni ), volcano harvest mouse ( Reithrodontomys chrysopsis ), and volcano rabbit ( Romerolagus diazi ), and Cryptotis goldmani alticola ,
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#1732788125350836-576: The adakitic imprint on the Trans-Mexican Volcanic Belt, prompted by the prolonged flat subduction of the Cocos Plate. Flat slab subduction can commonly be explained by oceanic plateau subduction and a fast overriding plate. Central Mexico's flat subduction is not evident. The Trans-Mexican Volcanic belt's flat slab is confined between ~101°W and 96°W; this region may be explained by thicker continental crust . Existence of thick strong crust combined with decreasing fluid input contributed to narrowing
874-651: The area. Resuming in the Eocene , post- Laramide deformation, subduction related volcanism formed the Sierra Madre Occidental silic volcanic arc at a paleo-subduction zone off the coast of Baja California , before the peninsula rifted away. From the Late Eocene to the Middle Miocene , counterclockwise rotation of the volcanic arc transitioned the once active Sierra Madre Occidental to
912-544: The asthenospheric wedge, increasing viscosity and suction forces, which led to flat subduction—preventing the oceanic plate from entering the mantle. From the west, the Trans-Mexican Volcanic Belt runs from Colima and Jalisco east through northern Michoacán , southern Guanajuato , southern Querétaro , México State , southern Hidalgo , the Distrito Federal , northern Morelos , Puebla , and Tlaxcala , to central Veracruz . The Mexican Plateau lies to
950-400: The belt have spurred several hypotheses based on a typical subduction scenario: intra-plate leaky transform faults , mantle plumes , continental rifting , and jump of the eastward Pacific Rise. These features are partially related to the reactivation of early fault systems during the Trans-Mexican Volcanic Belt's evolution. The main brittle fault system's geometry, kinematics, and age define
988-469: The belt that now sometimes strain the environment. Overgrazing Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves , or nature reserves . It can also be caused by immobile, travel restricted populations of native or non-native wild animals . Overgrazing reduces
1026-405: The biodiversity. Turning to the aquatic environment, Ling et al. (2015) have documented the phenomenon of catastrophic sea urchin overgrazing and its role in marine ecosystem regime shifts. Their study underscores the urgent need for effective management and conservation strategies to mitigate the profound ecological impacts of overgrazing, highlighting the issue's global scope. Similarly, on
1064-662: The breakup of the Farallon Plate at approximately 23 Ma, which created two plates at equatorial latitudes, the Cocos Plate and southern Nazca Plate . The Rivera Plate was the last fragment detached from the Cocos Plate, becoming a microplate at around 10 Ma. This small plate is bounded by the Rivera fracture zone, the East Pacific Rise , the Tamayo fracture zone, and the Middle American Trench. The larger Cocos Plate
1102-580: The dominant grass, with Calamagrostis tolucensis dominant between 3800 and 4200 meters. The transition from subalpine to alpine grasslands occurs between 4200 and 4300 meters elevation. Alpine grasslands are dominated by the grasses Festuca livida and Arenaria bryoides . Other alpine zone plants include Festuca tolucensis and species of Carex , Cerastium , Cirsium , Draba , Eryngium , Gnaphalium , Lupinus , Luzula , Oxylobus , Phacelia , Plantago , Potentilla , Ranunculus , and Senecio , together with ferns, mosses, and lichens. The flora of
1140-721: The north, bounded by the Sierra Madre Occidental to the west and Sierra Madre Oriental to the east. The Cofre de Perote and Pico de Orizaba volcanoes, in Puebla and Veracruz, mark the meeting of the Trans-Mexican Volcanic Belt with the Sierra Madre Oriental. To the south, the basin of the Balsas River lies between the Trans-Mexican Volcanic Belt and the Sierra Madre del Sur . This area
1178-484: The other high peaks, are active or dormant volcanoes . Other notable volcanoes in the range include (from west to east) Nevado de Colima (4,339 metres (14,236 ft)), Parícutin (2,774 metres (9,101 ft)), Nevado de Toluca (4,577 metres (15,016 ft)), Popocatépetl (5,452 metres (17,887 ft)), Iztaccíhuatl (5,286 metres (17,343 ft)), Matlalcueitl (4,461 metres (14,636 ft)) Cofre de Perote (4,282 metres (14,049 ft)) and Sierra Negra ,
Zacatonal - Misplaced Pages Continue
1216-872: The surrounding land in Australia. In the Caribbean region, overgrazing is a threat to vegetation areas where there is livestock farming, which is an important source of livelihood and food security for many people. a combination of small scale livestock farming with small ruminants, and mixed farming is practised. However, livestock consume vegetation faster than it can be renewed and this leads to land degradation, loss of vegetative areas, and soil erosion resulting in poor quality feed and reduced livestock yields and income. Also, these grazing lands are critical in controlling carbon dioxide and mitigating risks against severe weather such as floods and droughts. Overgrazing weakens ecological conservation. In New Zealand , overgrazing
1254-611: The threat to both flora and fauna . Many bird species have become extinct or endangered, and many of the medium-sized desert mammals are now completely extinct or only exist on a few islands of Australia . Overgrazing can also occur with native species. In the Australian Capital Territory , the local government in 2013 authorised a cull of 1455 kangaroos due to overgrazing. Maisie Carr (1912-1988), Ecologist and Botanist, undertook significant research and studies in overgrazing and established consequences on
1292-718: The transition between the lower-elevation pine-oak forests and the subalpine grasslands at about 3500 meters elevation. Grassland dominated by Toluca fescue ( Festuca tolucensis ) and Toluca reedgrass ( Calamagrostis tolucensis ) grows as an understory among the pines, in open Juniperus monticola woodland, or as open grassland. Other grasses and forbs include Arenaria bryoides , Descurainia impatiens , Draba jorullensis , Lupinus montanus , Muhlenbergia pusilla , M. quadridentata , Oxalis sp., Pedicularis orizabae , Penstemon gentianoides , Poa annua , Potentilla staminea , Sicyos parviflorus , and Trisetum spicatum . At 3800 meters elevation Muhlenbergia quadridentata becomes
1330-693: The use of common land in England and Wales was a triumph of conserving a scarce resource using agreed custom and practice. There have been overgrazing consequences in the region Sahel region. The violent herder–farmer conflicts in Nigeria , Mali , Sudan and other countries in the Sahel region have been exacerbated by land degradation and overgrazing. See 2010 Sahel famine . Various countries in Sub-Sahara Africa are affected by overgrazing and resulting ecological effects. In Namibia , overgrazing
1368-442: The usefulness, productivity and biodiversity of the land and is one cause of desertification and erosion . Overgrazing is also seen as a cause of the spread of invasive species of non-native plants and of weeds . Degrading land, emissions from animal agriculture and reducing the biomass in a ecosystem contribute directly to climate change between grazing events. Successful planned grazing strategies have been in support of
1406-483: The value of most ecosystem functions declines with increasing grazing intensity and that increasing aridity weakens positive impacts of light grazing. Native plant grass species, both individual bunch grasses and in grasslands , are especially vulnerable. For example, excessive browsing by white-tailed deer can lead to the growth of less preferred species of grasses and ferns or non-native plant species that can potentially displace native, woody plants, decreasing
1444-433: Was made of common land, for example in overgrazing, a common would be "stinted", that is, a limit would be put on the number of animals each commoner was allowed to graze. These regulations were responsive to demographic and economic pressure; thus rather than let a common become degraded, access was restricted even further. This important part of actual historic practice was absent from the economic model of Hardin. In reality
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