Análisis de la vegetación arbórea en la provincia florística de Tehuacán-Cuicatlán

The arboreal vegetation of a portion of the Tehuacán-Cuicatlán Valley is analyzed. An altitudinal gradient was followed along the leeward slopes of the Sierras de Juarez and Zongolica (Sierra Madre Oriental). Multivariate analysis techniques, ordination (principal component analysis and reciprocal averaging) and classification (informationanalysis program CENOSIS 2) were used. The results allow the definition of "groups" identifiable with vegetation types defined from a physiognomic-structural view point; however, the analysis performed shows that the arboreal vegetation of the study area possesses a variability and heterogeneity not detected by previous descriptive physiognomic studies. The importance of human disturbance and other factors (e.g. biotic interactions) affecting the structure and composition of the plant communities of the study area is discussed . The analysis techniques are compared with regards to their efficiency in handling high levels of vegetational heterogeneity , being the classification technique the most efficient one. Finally, some considerations judged interesting for future investigations are proposed.