摘要：Structure and floristic composition of a temperate forest of the Sierra Madre Occidental (SMO), in the state of Durango, Mexico, were analyzed in order to characterize the different plant strata. The study area is located at El Durangueño Ranch, with vegetation representative of the eastern slopes of the SMO. The area includes 3 dominant vegetation types: oak-pine forest, pine-oak forest and grassland. Floristic composition corresponds to semidry temperate forests and in smaller proportion to humid temperate forests of northern Mexico. Structural characteristics indicate that the sites present great heterogeneity, 26 species of grasslands, 31 in the oak-pine and 22 in the pine-oak, with the stratum under which presented more species 76. The trees are medium sized and the densities are similar to other sites of this mountain range. Oak-pine forests have the highest values of diversity and were similar to those registered in other areas of the SMO. There are 12 species endemic to Mexico, from which 6 are endemic to the SMO, and Psacalium cronquistiorum B.L. Turner (Asteraceae) is endemic of Durango. Seven species are included in the Red list of the IUCN. Grasslands have high floristic richness, combining species typical of the grasslands of lower elevations with species of temperate forests. Although there is no reference to fires in the forests of the area, the wide distribution of Quercus striatula scrub may indicate disturbance attributed to fires in the recent past.
关键词：oak-pine forest;pine-oak forest;grassland;point center quarter method;bosque de encino;bosque de pino;pastizal;cuadrantes centrados en un punto
