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CANYON OF THE ZOPILOTE REGION
The Canyon of the Zopilote River and neighbouring area southward beyond the state capital Chilpancingo and westward to the Sierra El Plateado cover 4383 km², situated between Mexico City and Acapulco in Guerrero, a state along the Pacific coast of south-western Mexico. The region is part of seven municipalities: Zumpango del Río, Chilpancingo, Chichihualco, Tlacotepec, San Miguel Totolapan, Atoyac de Alvarez and Coyuca de Benítez. It is in the Sierra Madre del Sur morphotectonic province and mainly in the Pacific Ranges and Cuestas subprovince (including the Sierra de Igualatlaco), with the northern lowlands in the Balsas Depression subprovince (Ferrusquía-Villafranca 1993).
The topography is generally mountainous, with c. 40% above 2000 m, and drainage mostly to the Balsas River in the north. The minimum elevation in the north-east is 600 m, in the north-west 2000 m. Important peaks ("cerros") include Yextla (2950 m) centrally, and in the south-west Teotepec (3550 m), Jilguero (2850-2900 m) and Tlacotepec (3330 m). Minimum elevations in the south-west and south-east are 800 m and 1600 m, within watersheds draining directly to the coast.
The region's geology is very complex (Ferrusquía-Villafranca 1993). Sedimentary rocks are the most prevalent, principally Mesozoic (Cretaceous) marine and transitional limestones. Igneous rocks are volcanic - extruded during the Cenozoic (e.g. basalts, andesites, tufas, breccias), or intrusive (e.g. granites, granodiorites).
The local weather is considerably influenced by the region's diverse topography. The general climate changes with increasing elevation from hot and dry in the lowland interior to warm to temperate and subhumid, to cool on the highest peaks. Generally there is a dry season during winter and spring, with precipitation mostly in summer through autumn. In the semi-arid area near Chilpancingo above Zopilote Canyon, the annual rainfall of 800 mm occurs mainly in May-November, and the mean annual temperature is 24°C with a 4.5°C oscillation and the extremes 5°C and 40°C; in May the diurnal fluctuation is 14°C (Rzedowski 1978). Higher in the mountains, precipitation may be over 1600 mm and temperatures become cooler, but the region includes many different restricted habitats, for example related to rain shadows and the full compass of slope aspects.
Of the ten principal vegetation types in Mexico, seven occur in the region (Rzedowski and Vela 1966; Rzedowski 1978; Fonseca and Lorea 1980). The varied topography and climate have resulted in a diverse mosaic. Along a north-east to south-west transect from Mezcala over the crest to Paraíso, the main formations are:
1. Deciduous tropical forest (500 m at Mezcala ascending to Xochipala). Many species of Bursera are characteristic, such as B. bonetii, B. longipes, B. morelensis, and columnar cacti especially in the canyon, such as Neobuxbaumia mezcalaensis and Pachycereus weberi (P. gigas).
2. With increasing altitude develops a transitional forest very rich in species, e.g. Ostrya virginiana, Cercocarpus macrophyllus, Juniperus flaccida and Actinocheita potentillifolia mixed with Quercus spp. from higher elevations. East of the transect near more arid Chilpancingo (1275 m) is xerophilous scrub, where Quercus magnoliifolia has become shrub-like (Miranda 1947), and Agave cupreata occurs on warmer slopes.
3. Oak forest (1500-2000 m), where the extreme minimum temperature may fall below 0°C. Predominant are Quercus glaucoides, Q. resinosa and Q. magnoliifolia.
4. Pine-oak forest (2000-2400 m or more) comprised of Pinus devoniana (P. michoacana), P. teocote and P. leiophylla, mainly with Quercus uxoris, Q. laurina, Q. acutifolia, Q. glaucescens and Q. crassipes.
5. Pine forest (above 2400 m) in less humid locales, with Pinus herrerae, P. leiophylla, P. ayacahuite and P. pseudostrobus var. oaxacana. The pine forest in some lower and warmer areas (not along this transect) is an association of just P. oocarpa and P. pringlei.
6. In more humid locales, an exuberant mesophyllous montane forest of several strata, with abundant climbers and epiphytes. Characteristic trees 30 m or more tall include Chiranthodendron pentadactylon, Chaetoptelea mexicana, Abies guatemalensis and Pinus ayacahuite. Shorter trees are Ostrya virginiana, Clethra mexicana, Styrax ramirezii, S. argenteus, Tilia occidentalis, Saurauia serrata, Viburnum ciliatum and Meliosma dentata. This community covers 40% of Omiltemi Ecological State Park.
7. Fir forest (2500-3000 m), with individuals of Abies religiosa and A. hickelii to 30 m tall. On the highest cerro Teotepec there is also a low forest of stout Pinus hartwegii; in rocky places grow Juniperus monticola var. monticola and rosette and cushion species of the páramo.
8. Descending the Pacific slope (below c. 2450 m) is a mesophyllous montane forest with a shrubby stratum rich in Melastomataceae, and many epiphytes - orchids, Peperomia and ferns. Characteristic trees include Podocarpus matudae, Pinus chiapensis, P. maximinoi, Chaetoptelea mexicana, Saurauia angustifolia, Hedyosmum mexicanum, Oreopanax obtusifolius, Dendropanax arboreus, Persea schiedeana, Drimys granadensis, Sloanea medusula and Magnolia schiedeana.
9. From 1570 m to 800 m toward Paraíso there is a very diverse subdeciduous tropical forest with species such as Licaria peckii, Persea schiedeana, Phoebe ehrenbergii, Hibiscus uncinellus, Synardisia venosa, Guarea glabra, Trophis chiapensis and Ardisia compressa.
The northern basically lowland portion of the Canyon of the Zopilote region is within the Balsas Depression Floristic Province (Rzedowski 1978), a centre important for endemic species and the spectacular diversification of Bursera species (Toledo-Manzur 1982). Most of the region is in the Middle Serranías Floristic Province, one of the major centres for endemics in Mexico, which includes the genera Silviella, Omiltemia, Microspermum, Peyritschia and Hintonella, and species such as Arracacia ovata, Coaxana bambusoides and Donnellsmithia ampulliformis. Endemism tends to be associated with high and humid locales, which function as isolated ecological islands.
The flora of this region and the whole state are not thoroughly known. Inventories suggest 30% of the 7000-7500 species in Guerrero are present. Some taxa have been more completely collected and studied, e.g. pteridophytes, Pinaceae, Lauraceae, Fagaceae, Melastomataceae, Araliaceae, Apiaceae, Rubiaceae and Orchidaceae. Arborescent ferns (e.g. Cyathea divergens, Lophosoria quadripinnata) are widely distributed in the general area. Peltogyne mexicana is a pre-Cenozoic tropical relict found in a few populations, which is also known from Panama and Colombia (Sousa-S. and Delgado-S. 1993). The taxonomic inventories illustrate the region's biological richness including 195 of the 207 estimated orchid species in Guerrero and half of the 351 collected species of pteridophytes (Lorea 1990). In the Canyon of the Zopilote occur 20 of the 64 species of Burseraceae reported for all of Mexico.
The region is very rich in timber resources. For general purposes including fuelwood, most used are the pines and oaks Pinus ayacahuite, P. devoniana (P. michoacana), P. chiapensis, P. herrerae, Quercus uxoris and Q. laurina, and as well Abies religiosa and A. guatemalensis; for particular construction, the palm Brahea dulcis, Cordia elaeagnoides and Pithecellobium dulce; and for artisanry and carvings, the preceding two hardwoods and Actinocheita potentillifolia.
Some species are used in local ceremonies, such as Bursera copallifera ("copal") and Solandra spp. ("copa de oro"). Among medicinals are Ternstroemia pringlei ("té de tila"), Juniperus flaccida, Magnolia schiedeana and Chiranthodendron pentadactylon ("flor de la manita") - which is now cultivated in Europe and U.S.A.
Social and environmental values
The Canyon of the Zopilote region harbours abundant diverse fauna, also not well known. A study of birds nearby to the south-west in the Sierra de Atoyac de Alvarez found 161 species, with 21 endemics (Navarro-Sigüenza 1986). Another study in that sierra reported 339 species of butterflies, 76% of the species known in Guerrero (Vargas 1990). The canyon is one of nine Mexican areas rich in endemic butterflies (Llorente-Bousquets and Luis-Martínez 1993). In Omiltemi Ecological State Park there are 37 species of amphibians and reptiles, with 13 endemics (Muñoz-Alonso 1988).
The Canyon of the Zopilote River is within the Sierra Madre del Sur of Guerrero and Oaxaca Endemic Bird Area (EBA A12), which has nine bird species of restricted range. Three of the four threatened birds within the EBA have significant populations in the canyon - the white-tailed hummingbird (Eupherusa poliocerca), short-crested coquette (Lophornis brachylopha) and white-throated jay (Cyanolyca mirabilis).
Proper management of the mesophyllous montane forests is essential to maintain their catchment of rainfall. For example, the Omiltemi forest captures over half the water for the city of Chilpancingo. The number of indigenous people inhabiting the region is small, in dispersed communities. They grow subsistence crops, and their impact on the vegetation is minimal.
The region also has archaeological importance. Xochipala was a pre-Hispanic ceremonial centre in 965 AD (Schmidt 1986). The northern area between Mezcala and Tetela del Río has evidence of human settlements of the Preclassic, Protoclassic, Classic and Postclassic periods (Rodríguez 1986). The regional variety thus offers potential for tourism, for example from Acapulco, Chilpancingo and Mexico City.
The region is accessible by all the major means of transportation. The general area's much-used major highway from the interior to the coast extends through the canyon and near the eastern edge of the region, and a railroad from the north terminates near the region's northern border at the Balsas River. From the south-west coast, a major road extends as far as Puerto del Gallo and connects by minor road with the principal road west of Chichihualco.
The Instituto Nacional de Investigaciones Forestales (INIF 1972) has pointed out the region's importance for forestry, with the highest timber volume in the state - estimated at 126-346 m3 per ha of coniferous forests with broadleaved trees (hardwoods) present, 91-245 m3/ha of coniferous forests with hardwoods codominant, and 110-233 m3/ha of hardwood forests with conifers present. By 1971, Guerrero may have provided up to 10.9% of Mexico's annual yield of saw timber (Styles 1993).
The state is fifth in Mexican coffee production, and the Canyon of the Zopilote region produces c. 70% of Guerrero's coffee. In the extreme south-west, the natural forest canopy has been left almost intact to shade the coffee plantations.
Farmers using the forest to shade their coffee plantations selectively cut mainly species of Pinus, Quercus and Ficus. With the population increasing, probably the road from Puerto del Gallo will be improved into a principal highway across the region and the railroad will be extended across to the coast. However, the greatest threat to the region is deforestation subsequent to commercial logging of coniferous and hardwood trees for the lumber and paper industries, without reforestation, and as well there is clandestine use by individuals. Many endemic species of flora and fauna are threatened by the deforestation.
This region is one of the few large and highly diverse areas remaining in Mexico that maintains relatively undisturbed native flora and fauna. Many plant communities still occur that elsewhere have been greatly altered or destroyed. Already the region has become a refuge for many threatened species.
Omiltemi Ecological State Park (17°31'-17°35'N and 99°30'-99°44'W) is 27 km west of Chilpancingo, including 36 km² of the western portion of the Sierra de Igualatlaco. The reserve was established in 1984 particularly for watershed management, through an agreement of the state governor and the Universidad Nacional Autónoma de México (UNAM) Facultad de Ciencias. Commercial export of Abies guatemalensis is prohibited by Appendix I of CITES.
Botanists from the UNAM Department of Biology's Vascular Plants Laboratory, who have been studying forests in Guerrero State for several years, suggest several communities that need to be protected: (1) the Abies forest (30 km²) on cerros Teotepec and Zacatonal (Map 16, zone C); (2) the adjacent area of mesophyllous montane and subdeciduous tropical forests (100 km²) between Puerto del Gallo and Paraíso (Map 16, zone A); (3) around Cerro Yextla (Map 16, zone B), by expanding Omiltemi park (30 km²) between Puerto Soleares and Cruz de Ocote the park harbours c. 1.4% of Guerrero's mesophyllous forest, yet 11% could be reserved in zones A and B; and (4) deciduous tropical forest in the Canyon of the Zopilote River.
Map 16. Canyon of the Zopilote Region, Mexico (CPD Site MA5), showing priority sites for conservation of plant communities
Ferrusquía-Villafranca, I. (1993). Geology of Mexico: a synopsis. In Ramamoorthy, T.P., Bye, R., Lot, A. and Fa, J.E. (eds), Biological diversity of Mexico: origins and distribution. Oxford University Press, New York. Pp. 3-107.
Fonseca, R.M. and Lorea, F. (1980). Recursos bióticos de la cuenca del Río Zopilote, area Filo de Caballo. Universidad Nacional Autónoma de México (UNAM), Fac. Ciencias, Archivo de la Comisión de Biologías de Campo, Mexico, D.F. 42 pp. Unpublished report.
INIF (1972). Inventario forestal del estado de Guerrero. Secretaría de Agricultura y Ganadería (SAG), Subsecretaría Forestal y de la Fauna, Instituto Nacional de Investigaciones Forestales (INIF) Publ. No. 24. Mexico, D.F. 66 pp.
Llorente-Bousquets, J. and Luis-Martínez, A. (1993). Conservation-oriented analysis of Mexican butterflies: Papilionidae (Lepidoptera, Papilionoidea). In Ramamoorthy, T.P., Bye, R., Lot, A. and Fa, J.E. (eds), Biological diversity of Mexico: origins and distribution. Oxford University Press, New York. Pp. 147-177.
Lorea, F. (1990). Estudios pteridológicos en el estado de Guerrero, México (Diversidad, distribución y relaciones fitogeográficas de la pteridoflora). Thesis. UNAM, Mexico, D.F. 43 pp.
Miranda, F. (1947). Estudios sobre la vegetación de México. V. Rasgos de la vegetación en la cuenca del Río de las Balsas. Rev. Soc. Mex. Hist. Nat. 8: 95-114.
Muñoz-Alonso, L.A. (1988). Estudio herpetofaunístico del Parque Ecológico Estatal de Omiltemi, Mpio. de Chilpancingo de los Bravo, Guerrero. Thesis. UNAM, Mexico, D.F. 111 pp.
Navarro-Sigüenza, A.G. (1986). Distribución altitudinal de las aves en la Sierra de Atoyac, Guerrero. Thesis. UNAM, Mexico, D.F. 79 pp.
Rodríguez, F. (1986). Desarrollo cultural en la región de Mezcala-Tetela del Río. In Primer Coloquio de Arqueología y Etnohistoria del Estado de Guerrero. Instituto Nacional de Antropología e Historia (INAH), Mexico, D.F. Pp. 155-170.
Rzedowski, J. (1978). Vegetación de México. Editorial Limusa, Mexico, D.F. 432 pp.
Rzedowski, J. and Vela, L. (1966). Pinus strobus var. chiapensis en la Sierra Madre del Sur de México. Ciencia (México) 24: 211-216.
Schmidt, P. (1986). Secuencia arqueológica de Xochipala. In Primer Coloquio de Arqueología e Historia del Estado de Guerrero. INAH, Mexico, D.F.
Sousa-S., M. and Delgado-S., A. (1993). Mexican Leguminosae: phytogeography, endemism, and origins. In Ramamoorthy, T.P., Bye, R., Lot, A. and Fa, J.E. (eds), Biological diversity of Mexico: origins and distribution. Oxford University Press, New York. Pp. 459-511.
Styles, B.T. (1993). Genus Pinus: a Mexican purview. In Ramamoorthy, T.P., Bye, R., Lot, A. and Fa, J.E. (eds), Biological diversity of Mexico: origins and distribution. Oxford University Press, New York. Pp. 397-420.
Toledo-Manzur, C.A. (1982). El género Bursera (Burseraceae) en el estado de Guerrero. Thesis. UNAM, Mexico, D.F. 182 pp.
Vargas, I. (1990). Listado lepidopterofaunístico de la Sierra de Atoyac de Alvarez en el estado de Guerrero. Nota acerca de su distribución local y estacional (Rhopalocera: Papilionoidea). Thesis. UNAM, Mexico, D.F. 149 pp.
This Data Sheet was written by Nelly Diego, Rosa M. Fonseca, Francisco Lorea, Lucio
Lozada and Lino Monroy [Universidad Nacional Autónoma de México (UNAM), Laboratorio de
Plantas Vasculares, Departamento de Biología, Facultad de Ciencias, Circuito exterior,
Ciudad Universitaria, Mexico 04510, D.F., Mexico].
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