The relationship between pedogenic and geomorphic processes in mountainous tropical forested area in Sierra Madre del Sur, Mexico

Both mature and underdeveloped soils are present in tropical mountainous landscapes. The spatial arrangement of mountainous soils is ascribed mainly to geomorphologic processes. We studied two soil toposequences (one on a convex, and the other on a concave slope with a gradient 40-60%) at the coffee-growing farm La Cabaña, situated in the mountains of the Sierra Madre del Sur, southern Mexico. Mature (Alisols) as well as moderately developed (Luvic Phaeozems) and underdeveloped soils (Fluvic and Skeletic Phaeozems) were detected in the study area. The sequence of sediments and soils is unusual for a classical soil catena. Buried clayey reddish soils are present on the shoulder of a slope; colluvial sediments with weakly developed soils form convex and concave footslopes. The peculiarity of the slopes and spatial distribution of soils in the studied toposequences were ascribed to intensive linear erosion (due to tectonic uplift), seismically induced landslides, and K-cycles of laminar erosion. The diversity of sediments leads to considerable variation in soil texture and mineralogical composition, and, thus, to the diversity of soil properties, which is considered to be a positive feature of a landscape.