Abstract
Nine sites of mixed-conifer forests where the Mexican yew (Taxus globosa) inhabits in the Sierra Madre Oriental at the States of Nuevo Leon and Tamaulipas were sampled. We quantified the basal area, density, canopy cover, height and number of plants of the associate species, as well as altitude, topographic aspect, slope, and stoniness. The sampled sites were divided in northern and southern sites according to their distribution in the study area and their attributes were compared with t tests. A Shannon-Wiener diversity index was calculated for each site and a Hutcheson t test was applied to find differences in diversity values between sites. The importance value for each species per site was calculated and the information of the nine forest sites was evaluated by means of cluster analysis, using only those species with importance value of ??5% in at least one site. The t tests showed that both basal area and plant height were different between the northern and southern sites, as were altitude and slope; the other variables showed statistical equality. The higher diversity was found at inaccessible sites such as El Butano and in areas far away from urban zones such as Las Tinajas. The sites without differences regarding their diversity indices are geographically closer to each other. The dendrogram showed that La Camotera and El Rumbadero, along with Potrero had the highest similarity. Abies vejarii subsp. mexicana, Juglans mollis, Quercus rysophylla and Tilia mexicana are the most common species in the forests where Taxus globosa var. floridana inhabitat.