Pedogenesis and spatial and functional structure of plant communities in alpine cold screes.

• Main Author: Meynier, Simon
• Other Authors: Laboratoire des EcoSystèmes et des Sociétés en Montagne (UR LESSEM), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université Grenoble Alpes 2020-., Grégory Loucougaray
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Soil organic matter; Mountain; Climatic gradient; Cold screes; Boreo-Alpine flora; Soil-Plant interaction modelling; Éboulis froids; Microrefuge; Écologie; Réchauffement climatique; Communautés végétales; Formes d'humus; Structure spatiale; Traits fonctionnels; [SDE.MCG]Environmental Sciences/Global Changes; Arctic; Global warming
• Online Access: https://theses.hal.science/tel-04145219; https://theses.hal.science/tel-04145219/document; https://theses.hal.science/tel-04145219/file/MEYNIER_2023_archivage.pdf

Cold screes are porous formations found in the Alps down to the lower montane level. Governed by a complex system of reversible internal ventilation depending on the atmospheric temperature, they are characterized by a strong negative anomaly of ground temperature, while the atmospheric temperature remains identical to the adjacents environments at only 2m from the ground. This very particular abiotic context causes the appearance of "abyssal" ecological islands, abnormally low in altitude and/or latitude, in the zones constantly cooled by the ventilation system. In these abyssal islands, a boreo-arctic flora, dwarfed trees, and soils with a high accumulation of organic matter contrast strongly with the spruce or beech-fir forest of the surrounding montane or subalpine zone. Some species with a wide ecological range from adjacent environments manage to coexist with species specialized in the cold conditions provided by the cold screes. These singular formations thus constitute a suitable study model to investigate, especially in the context of global warming, the effects of soil temperature on the ecological processes of cold ecosystems.The general objective of this work is (i) to improve the scarce existing knowledge on the ecological specificities of cold screes, and (ii) to study, in the context of global warming, the effects of soil cold on pedogenesis, and, at the scale of life forms, on the spatial structure of plant communities, as well as the functional strategies and trade-offs of plants present in abyssal islands.Overall, this work highlights the fact that the environmental context specific to each scree - bedrock, exposure, atmospheric climate, local species pool, microtopography - greatly influences the soil and taxonomic composition of plant communities, resulting in high variability in these characteristics among the cold screes studied. Yet, the low soil temperature, common to each site, is the predominant factor in abyssal ecosystem functioning. Thus, the spatial structure and functional ...