The distribution of high mountain vegetation in relation to snow cover: Pen˜alara Spain

This research examines how snow accumulation, and erosion processes associated with it, influences the distribution of vegetation. Studies were conducted on Pen˜alara Massif (2428 m above sea-level (a.s.l.)), in the centre of the Iberian Peninsula (40°50′N, 3°58′W). The designated area is on the eastern slope between 1800 and 2400m a.s.l. A detailed vegetation map was developed and was used to select two key areas in each of the three altitudinal zones, located between 18(10 and 2000, 2000 and 2200, and 2200 and 2400m a.s.l. Each key area was determined in relation to the highest concentration of contrasts in vegetation in a limited space. The authors examined the most unstable landforms, the areas with the sparsest vegetation and the zones that had the greatest snow accumulation. Once these three criteria were superimposed, area types emerged that showed a high sensitivity to erosion. Each area was divided crosswise into two sections. A detailed study of each section was conducted and included the analysis of landforms, the application of inventories to strategic plots to determine the distribution of plant species, and the monitoring of active erosion processes and snow conditions from 1991 to 1995. Results showed that if the relief is uniform, vegetation tends to be distributed in homogeneous altitudinal belts. However, if the terrain is marred by obstacles composed of loose sedimentary material that descend in the direction of the slope, the snow action will become an important factor in the distribution of vegetation. The plant associations will colonize in belts that run parallel to the slope.