GEOMORPHIC PROCESSES ABOVE TIMBERLINE IN THE SPANISH PYRENEES

Presents a general account of geomorphic processes effective above timberline in the Spanish Pyrenees with emphasis on the central section of the range. Climatic and environmental factors are discussed in detail as well as the geomorphic responses to lowering of the upper timberline, especially between the sixteenth and nineteenth centuries. During this period expansion of livestock grazing reduced the forest cover extensively and caused a substantial lowering of the lower altitudinal limit of periglacial activity. Relic periglacial forms are attributable to the Late Quaternary Period, although many active forms are present today. These include rock glaciers, solifluction lobes and terracettes, and various types of patterned ground. Altitude, exposure, slope gradient, and lithology are shown to be important determinant factors, together with the increasing degree of continentality in the Central Pyrenees compared with areas further west and east respectively. The high mountain region is divided into two altitudinal belts with the 2400 m level forming the general boundary. -Authors