Humus forms pathways in low-elevation cold scree slopes: Tangel or Mor?

• Published in: Applied Soil Ecology
• Main Authors: Meynier, S., Brun, J.J.
• Other Authors: Laboratoire des EcoSystèmes et des Sociétés en Montagne (UR LESSEM), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDE]Environmental Sciences; The Chimney; permafrost
• Online Access: https://hal.inrae.fr/hal-02608966; https://doi.org/10.1016/j.apsoil.2017.10.017

[Departement_IRSTEA]Territoires [ADD1_IRSTEA]Adaptation des territoires au changement global International audience Low-elevation cold scree slopes are characterized by a remarkable abiotic phenomenon: an internal air circulation, the chimney effect, which leads to a strong negative anomaly of temperature in their lower part, potentially resulting in the formation of underlying permafrost lenses at very low altitude (< 1500 m in the Alps). The aim of this study was to better understand humus forms of the five cold screes known in the Isere department (French Alps). We tested two alternative hypothesizes: (i) despite an atypical abiotic context, the humus forms of the cold screes are following the two theoretical pathways under colder conditions, leading to Mor humus forms (acidic context) or scarcely known Tangel (calcareous context). (ii) The micro-scale varying vegetation type within the coldest area of the scree may induce some differences in humus profile and soil organic matter. Surprisingly, we did not find any significant vegetation influence either on humus profile or organic matter throughout the OF-OH-A (H) layers. Moreover, among the four pedogenesis we observed, three were unusual (intermediate Tangel/Mor humus in calcareous context, plus peculiar Tangel and Histomor humus), while only one was fully consistent with its usual pathway (Mor humus in acidic context). Our results suggest that the underlying abiotic conditions (bedrock, soil temperature and moisture) of the cold scree slopes outweigh vegetation and atmospheric climate as dominant drivers of the ecosystem functioning. This remarkable context may impact the complex abyssal environment within cold screes, leading to divergences from regular ecological pathways.