The use of digital methods in assessing forest patterns in an Andean environment: The Polylepis example

The distribution of Polylepis forest on the flanks of Sajama Volcano in the Western Cordillera of Bolivia was determined using remote-sensing and GIS methods. Based on a digital elevation model, computer simulated solar irradiance, and LANDSAT-MSS data, the meso-scale distribution and vitality of Polylepis tarapacana shrubs were analyzed; the results are supported by climatic and microclimatic measurements taken in the forest habitats. The spatial distribution pattern of the forests is strongly coincident with the daily variation in soil temperatures in the root zone. On north-facing slopes that receive adequate solar irradiance, soil temperatures are high while relative atmospheric humidity is low. On south-facing slopes soils are frozen when atmospheric water content is low.