Location and General Description
The region is formed by the lower elevations of the Sierra Madre Oriental that gradually diffuse into the northeastern coastal province of Tamaulipas. One part of the region is composed of abrupt mountains, but low valleys and vast plateaus mostly dominate it. Geologically, sedimentary rocks of marine origin characterize the ecoregion. These rocks are characteristic for their abundant faults and folding (Ferrusquía-Villafranca 1993). The climate is dry, and precipitation levels are below 1000 mm/year.
Botanically, the region is composed of a desert scrub that is different from the plant associations occurring in the Chihuahuan Desert or in the Central Plateau. Dominant plant species are Opuntia leptocaulis, O. lindheimeri, Prosopis juliflora, P. laevigata, Yucca treculeana, Salvia ballotaeflora, Jatropha dioica, cenizo (Leucophyllum texanum), Mammillaria hemisphaerica, tepeguaje (Leucaena pulverulenta) and Mimosa biuncifera, among many others. At the base of the Sierra Madre Oriental mountains, shallow soils derived from sedimentary rocks support a particular community known as piedmont scrub. This scrub is composed of relatively short plants (3 to 5 m) growing in dry environments (450-900 mm/year) at altitudes below 2000 m. Dominant species are Helietta parvifolia, Neopringlea integrifolia and Acacia spp. Also near the Sierra Madre Oriental, a montane chaparral grows on regions above 1700m. In these areas Quercus is the dominant genus but Arbutus, Yucca, Cercocarpus and Bauhinia can also be found. The scrub is generally well represented by many leguminosae, and the herbaceous stratum in this region is rich in species (Marroquín et al. 1981).
The Tamaulipan matorral constitutes a unique assemblage of plant and animal species, and due to the geological history of the region, has outstanding biodiversity features. This region has high numbers of endemic cacti that are greatly appreciated, and also exploited, by foreign collectors. The region is considered among the priority areas for conservation of succulents (Oldifield 1997). An important portion of the habitat for Agave victoria-reginae, an endemic species, lies in this ecoregion. The region is considered as a center of radiation and speciation of the plant family Lamiaceae (Ramamoorthy & Elliot 1993). It also contains at least four endemic genera of woody plants including Clappia, Nephropetalum, Pterocaulon and Runyonia (Rzedowski 1978). Of the 151 species of endemic agavaceae that live in Mexico, 75 have restricted distributions in areas that served as "ecological" islands in the past; the Tamaulipan matorral is one of these areas (García-Mendoza 1995).
In addition, this ecoregion provides habitat for the highly endangered Mexican prairie dog (Cynomys mexicanus) (Challenger 1998). Other mammal species present in this xeric ecoregion include Saussure’s shrew (Sorex saussurei), yellow-faced pocket gopher (Pappogeomys castanops), and Allen’s squirrel (Sciurus alleni), collared peccary (Pecari tajacu) and coyote (Canis latrans) just to name a few (Goldman 1946). Many bird species also utilize this ecoregion such as the burrowing owl (Athene cunicularia), hooded oriole (Icterus cucullates), eastern meadowlark (Sturnella magna), long-billed thrasher (Taxotoma longirostre), hooded yellowthroat (Geothlypis nelsoni), blue bunting (Cyanocompsa parellina) and olive sparrow (Arremonops rufivirgatus).
Despite being situated in a highly populated area of Mexico, the Tamaulipan matorral is still in relatively good condition. Few protected areas however have been established to protect this region, although several have been proposed to be established. The main challenge lies in achieving good management programs that take into account the needs of the local villagers and combine them with biological conservation goals.
Types and Severity of Threats
The main threats are land conversion for agriculture, goat, sheep and cattle farming, livestock grazing, collection of plants and animals and urban expansion. In the valley of Jaumave, the land is commonly converted to agricultural fields by the burning of native vegetation. Cacti and other succulents, some of which have very narrow distribution, are badly damaged or die during this process. Most of the fires are uncontrollable (Oldfield 1997), constituting a major threat to the plant communities of the region. Construction of dams, road opening, mining and expansion of urban areas also causes habitat destruction. Besides these, illegal extraction and trade of exotic plant species has lead many cacti to acquire endangered status. Some desert animals have long been considered "enemies" to human communities or their domestic fauna; thus they have been deliberately and intensely removed from their original habitat. For example, intentional poisoning has made the Mexican prairie dog one of the most endangered species of mammals in Mexico (Miller et al. 1994).
Justification of Ecoregion Delineation
This matorral ecoregion is limited to the lower elevations of the Sierra Madre Oriental in northeastern coastal state of Tamaulipas and southern Nuevo León, and is thus isolated from other similar habitats. Delineation’s for this ecoregion follow INEGI (1996), from which we lumped the following vegetation classifications: "sarcocaulous matorral", "crasicaulous matorral", and portions of "agricultural landuse". Reference was also made to Rzedowski (1978), and reviews and revisions to the linework were done by expert opinion at several ecoregional priority setting workshops (CONABIO 1996 and 1997).
Challenger, A. 1998. Utilización y conservación de los ecosistemas terrestres de México. Pasado, presentey futuro. México: Conabio, IBUNAM y Agrupación Sierra Madre.
CONABIO Workshop, 17-16 September, 1996. Informe de Resultados del Taller de Ecoregionalización para la Conservación de México.
CONABIO Workshop, Mexico, D.F., November 1997. Ecological and Biogeographical Regionalization of Mexico.
Ferrusquía-Villafranca, I. 1993. Geología de México: una sinopsis. Pages 3-108 in T. P. Ramamoorthy, R. Bye, A. Lot, y J. Fa, (editors). Diversidad Biológica de México. Orígenes y Distribución. Mexico: Instituto de Biología, UNAM.
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Marroquín, J.S., G. Borja, R. Velázquez, y J.A. de la Cruz. 1981. Estudio ecológico y dasonómico de las zonas áridas del norte de México, Publicación Especial 2. México: Instituto Nacional de Investigaciones Forestales, SARH.
Miller, B., G. Ceballos, and R. Reading. 1994. The prairie dog and biotic diversity. Conservation Biology 3: 677-681.
Oldfield, S. (Comp). 1997. Cactus and succulent plants. Status survey and conservation action plan. U.K.: IUCN, Cambridge.
Ramamoorthy, T. P., y M. Elliott. 1993. Lamiaceae de México: diversidad, distribución, endemismo y evolución. Pages 501-526 in T .P. Ramamoorthy, R., Bye, A. Lot, y J. Fa, (editors). Diversidad Biológica de México. Orígenes y Distribución. Mexico: Instituto de Biología, UNAM.
Rzedowski, J. 1978. Vegetación de Mexico. Editorial Limusa. Mexico, D.F., Mexico
Prepared by: Alejandra Valero, Jan Schipper, and Tom Allnutt