Delineation of biogeomorphic land units across a tropical natural and humanized terrain in Los Tuxtlas, Veracruz, México

This paper analyzes landscape in a rainforest region integrating geomorphologic and ecosystem analysis methods. Major landscape elements (geology, geomorphology, soils, vegetation and land use) were mapped as biogeomorphic land units using remote sensing and geographic information systems (GIS). Associations between these variables were analyzed by map fusion and the results were expressed on a land unit map (scale ca. 1:100,000). Volcanic structures are dominant in the study area. Lava flows cover most of the region, mainly as basalt; several pyroclastic cones are widely distributed over the area but are dominant in the southeast region. A hypsometric map derived from a digital elevation model (DEM), and intersected with a land cover/use map showed an altitudinal gradient of vegetation. Rainforest grows at lower altitudes (0 to 700 m) and Virola, Juglans and Chionantus are distributed from 700 to 900 m. These species are located on slopes of basalt and andesites intercalated with tephra, recent isolated stratovolcano structures and an erosive flood plain. At higher altitudes (900 to 1100 m) the forest identified as Chionantus‒Ulmus‒Randia is associated with cinder cones. A Quercus‒Ulmus forest (900 to 1400 m) covers the slopes of the highest volcano (San Martin) and surrounding areas, while evergreen (elfin) forest is at the top of this mountain (1660 m).