Do periglacial landscapes evolve under periglacial conditions ?
Résumé
Abstract Polar and Alpine periglacial areas are traditionally regarded as necessarily submitted to very efficient frost-driven processes that control the Holocene and ongoing geomorphic activity. During the last decade, the validity of this academic view has been increasingly questioned among the international scientific community. The search for the real past and present processes responsible for landform evolution in cold non-glaciated areas is based mainly on more and more refined monitoring protocols relying upon sophisticated equipment. To assess the representativeness and significance of monitoring data collected in restricted sites, it appears necessary however to widen the perspective by adopting a twofold multiscale approach as proposed in the present paper : (1) in space, by integrating various scales from the general slope system to the bioclimatic nanoenvironment ; (2) in time, by taking into account the landscape history, from Tertiary inherited features to recent process changes induced by the contemporary warming. Reintegrating the historical approach should help both to place the ongoing processes within a succession and/or combination of interoperating processes, and to avoid misinterpretations of features considered wrongly as emblematic of frost action. Overall, both the historical and monitoring approaches tend to reduce the geomorphic efficiency of frost-derived processes. Instead, the role of non cold-related processes, such as chemical, thermal, biogenic and rainfall-induced ones, is being emphasized. Of special interest would be an interdisciplinary discussion between geomorphologists and various disciplines of biological sciences including biochemistry and ecology studying processes of primary successions.