ANDEAN SOIL-EROSION

Field observations and simulated rainfall experiments in two watersheds in the Ecuadorian Andes show high rates of soil erosion in both, although soil, climatic, agricultural, and cultural factors differ between the two. Intra-watershed variability of infiltration and runoff is high, and compacted surfaces, such as roads and trails, play a key role in generating erosive surface flows. Land-use characterizes erosion rates better than soil types do in these watersheds. Recently tilled cropland yielded the greatest rainfall erosion losses in the 1300-km2 Rio Ambato watershed, whereas abandoned cropland generated the most sediment in the 5186-km2 Rio Paute watershed. The erosional importance of abandoned lands underscores the need for a broad view of soil-erosion causation and soil conservation in occupied mountain landscapes.