RELATIONS AMONG TREE COMMUNITIES, SOIL AND THE ALTITUDINAL GRADIENT IN THE TEQUILA VOLCANO, JALISCO STATE

Abstract

Quantitative studies about vegetation in Mexico have focused on tropical and cloud mountain forests, compared to which those of temperate forests are relatively scarce. Many have described light as a directing force in the distribution of resources among species; however, some such as soil nutriments have received less attention. In this paper is described the community structure of a mild-weather forest community along an altitudinal gradient of Tequila Volcano, in the state of Jalisco; the analysis was made according the α and β diversity, as well as soil variables relationships by ordination techniques, that explained 97 % of total variation; the most important variables were altitude, clay content, potassium, pH, electric conductivity, nitrites, sand, nitrogen, phosphorous and calcium. Tree richness showed a unimodal response in regard to altitude, with a maximum value between 2 000 a 2 350 m asl. Finally, the greatest species turnover rate occurs between the places with the highest altitude and those of the lowest (1.0). In Tequila Volcano there is a niche differentiation among species, which is due to the distribution of edaphic resources along the altitude gradient, which is acknowledged as the major mechanism that keeps the tree diversity in the temperate portion of the study area.