MULTIVARIATE-ANALYSIS OF THE VEGETATION OF THE VOLCANOS TLALOC AND PELADO, MEXICO

Abstract

Multivariate analysis was used to describe the composition and distribution of vegetation types on the slopes of the volcanoes Tlaloc and Pelado, Mexico. These volcanoes are situated in the transitional zone between the Holarctic and Neotropical floristic regions, which offers a partial explanation for the relatively high alpha and beta diversities. Previous research argued that human activities, i.e. burning and razing, rather than abiotic factors, play a major role in determining the distribution and floristic composition of the vegetation. TWINSPAN, Detrended Correspondence Analysis and Canonical Correspondence Analysis were used to test this hypothesis. Floristic and environmental data from 138 releves and seven explanatory environmental variables were included: elevation, soil depth, soil moisture, percentage litter cover, percentage cover of bare ground, burning and grazing were included in the analysis. Soil moisture and elevation accounted for ca. 63 % of the residual inertia and none of the remaining explanatory variables proved to be correlated significantly with the first two axes. The present results suggest that burning and grazing operate on a finer scale. In conclusion, soil moisture and elevation are the most relevant variables to explain the distribution of the vegetation under study.