Michel Lecompte

Dynamic phytoclimatology, an aid to spatial generalisation of external geodynamical studies

Abstract The statistics and mechanical studies of the spatial variability of rainfall do not seem to be entirely satisfactory for brief events, such as the showers generating gullying. Thus, indirect indications of vegetation may be useful. Botanical continuums do reflect some climatic changes that may be linked to the distribution of these events. As an example, the analyses of some floristic transects, located at the transition of Mediterranean and oceanic, and Mediterranean and arid climates are presented. Conducted in parallel with the dynamic interpretation of climatic fields, these analyses have, for instance, allowed to state more precisely the spatial extension of several features of rains such as their cumulated values and their regime. The floristic ‘signal’ mainly concerns the climatic variations of the cumulated value of rainfall, but, in a subtler way, vegetation may signal the variations of regime. These features are linked with the strength of showers, and, as a consequence with the erosive capacity of rainfall. Dynamic phytoclimatology is then liable to give an aid to the spatialization of external geodynamic studies.

Maris Gullying: canonical analysis of erosion and sedimentation sequences (Baronnies - France)

AbstractThe gullying action on Jurassic and Cretaceous marls in the Baronnies is observed, warm season after cold season, thanks to a network of measuring stakes arranged in 12 gullies. The climate, characterized by summer heath, rather cold but luminous winters, and quite heavy rain, can be classified as mountainous-mediterranean. Seasonal ablation/sedimentation measures have been carried out upon 119 stakes five times within two years (768 days): two in automn, two in early spring (april), and one at end-of-spring.Ablation and sedimentation sequences are described among the stakes population by Correspondance Factor Analysis (CFA), and their covariations in space and time are explained by Canonical Correspondance Analysis (CCA) according to biophysical environment variables.Axis 1 of the CFA opposes ground level variations according to their amplitude, high or moderate, regardless of the direction of variation and of measurement date. Axis 2 presents a temporal variation, opposing, on one side, sediment...