Eduardo Estrada Castillón

Leguminosas del norte del estado de Nuevo León, México

A study of the diversity of legumes in the northern part of the state of Nuevo Leon was undertaken. 38 genera, 94 species and 26 infraspecific taxa of legumes were recorded. The family Fabaceae comprises 18 genera and 42 species, Mimosaceae 10 and 30 and Caesalpiniaceae 10 and 22 respectivelly. The genera with highest number of species are Acacia (12), Dalea (10), Mimosa (6), Senna (5), Caesalpinia (4) and Bauhinia (4). Shrubby legumes are the most abundant in the zone, representing 47% (46 species); the herbaceous ones constitute 46% (45) and the arboreal ones comprise 7% (7). The highest number of taxa was recorded on semithorn shrubland (52) piedmont scrub (48), oak-pine forest (44), while the mezquite shrublands shelter the lowest number of species (23).

VACÍOS Y OMISIONES EN CONSERVACIÓN DE LAS ECORREGIONES DE MONTAÑA EN MÉXICO

Mountains are ecosystems that harbor great biodiversity and represent important source of environmental services to society. In the present study it was determined for the class 5 mountains (Kapos classification) of Mexico in level IV ecoregions, their level of representation in protected areas and their vegetation and land use coverage, following the methodology developed by the gap analysis program (GAP) of the USA. In 45 of the 99 ecoregions of Mexico exist mountains which cover 20,109,804 hectares, representing 10.3% of the country. The mountains are present in the seven categories of level I ecoregions of Mexico: Great Plains, North American Deserts, California Mediterranean, Southern Semi-Arid, Temperate Sierras, Tropical Dry Forests and Tropical Humid Forests. The 30.1% of Temperate Sierras ecoregions surface are mountains, while they cover only 2.1% of the Great Plains ecoregion territory. In Mexico, only 14.4% of protected areas surface corresponds tomountains, while worldwide, 32% of protected areas are located in these ecosystems. The natural vegetation of mountains represents11.9% of this type in Mexico and 11.5% of primary vegetation, while areas with anthropic uses represent only 2.9%, well below the 13.3% recorded worldwide. Ecoregions of the Sierra Madre del Sur are the second largest covered mountains of Mexico with 20.5%, after those in the Sierra Madre Occidental (25.3%). This situation is alarming, given the high rate of deforestation recorded in southeastern Mexico, where only 21.4% of its territory has primary vegetation, compared to 49.3% for Mexico. Actions are needed to adequately protect mountain ecosystems in Mexico, given special attention to southeast region of the country.

Classification and ordination of main plant communities along an altitudinal gradient in the arid and temperate climates of northeastern Mexico.

Quantitative data on the ecology of the main plant communities along an altitudinal gradient in northeastern Mexico were obtained with the aim of identifying the most important environmental variables that affect plant distribution and composition. The main threats to these communities were also investigated. Importance value index (IVi) of the 39 most important species and 16 environmental variables were recorded at 35 altitudinal gradients each spaced at intervals of at least 100-m altitude. Classification and ordination of vegetation showed six well-differentiated but overlapping plant communities: alpine meadow, cold conifer forest, mesic mixed forest, xeric scrub, Tamaulipan piedmont scrub, and halophytic grassland. Altitude, minimum and average temperatures, and organic matter content are the main variables affecting the plant distribution in northeastern Mexico. Urban growth, mechanized agriculture, and changes in land use are the main threats in the short and medium term to plant communities in this area. Climate change also seems to be having an impact at present or in the near future as shown by the presence of exotic shrubs from warmer areas in mesic and temperate areas inhabited by oak and oak-pine forest.

Livestock Effect On Floristic Composition and Vegetation Structure of Two Desert Scrublands In Northwest Coahuila, Mexico

Abstract Microphyllous and rosetophyllous desert scrub plant communities dominate large parts of the state of Coahuila, Mexico, yet differences in how livestock grazing impacts these two plant communities are not well documented. In order to address this knowledge gap, we assessed livestock impact on plant species composition and vegetation structure in microphyllous and rosetophyllous desert scrublands in this northwestern Mexican state. We collected plant density, frequency, and cover data from sites with and without livestock grazing pressure that were otherwise similar in plant composition. We quantified intersite differences using the importance value index (IVI) and the Bray-Curtis similarity index. The species with the highest IVI for microphyllous scrubland were lechuguilla (Agave lechuguilla), honey mesquite (Prosopis glandulosa), and creosote bush (Larrea tridentata); however, in sites with presence of domestic herbivores, desert willow (Chilopsis linearis) and spiny hackberry (Celtis pallida) also showed high values. Plant species with the highest IVIs in rosetophyllous scrublands were lechuguilla, creosote bush, mariola (Parthenium incanum), and blue grama (Bouteloua gracilis) for both land use types. The Bray-Curtis similarity index between microphyllous desert scrub and rosetophyllous desert scrub was 62%. Moreover, microphyllous scrub with and without livestock had 48% similarity, whereas rosetophyllous scrub sites with and without livestock were 65% similar. Results indicate that livestock grazing significantly modifies plant species composition and vegetation structure in both types of the studied desert scrublands.

Peniocereus greggii Variety Greggii (Cactaceae) in Durango, Mexico

Abstract Peniocereus greggii variety greggii is a protected species that is collected illegally in Parque Estatal Cañón de Fernandez. It is associated with fertility islands formed by mesquites Prosopis glandulosa and P. laevigata. It has a root that is used as food, it can be used to treat kidney problems, and it is a cardiac stimulant. Resumen Peniocereus greggii variedad greggii es una especie protegida y saqueada ilegalmente del Parque Estatal Cañón de Fernández. Se asocia con islas de fertilidad formadas por mezquites Prosopis glandulosa y P. laevigata. Posee una raíz que se utiliza como alimento, puede ser utilizado para tratar problemas renales, y es un estimulante cardiaco.