From specific production to homogenisation of dissolved organic matter produced by vegetation

• Main Author: Allain, Alienor
• Other Authors: Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Bourse ministérielle de thèse de doctoratEC2CO DYNAMOET-TK, Sorbonne Université, Maryse Rouelle, Marie Alexis
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Vegetation cover – biodegradation – Incubation – Arctic - Terrestrial environments - HRMS Orbitrap; Couverture végétale – Biodégradation – Incubation – Arctique – Environnements terrestres – HRMS Orbitrap; [SDE]Environmental Sciences; Arctic; Arctique*
• Online Access: https://cnrs.hal.science/tel-03979367

Although dissolved organic matter (DOM) represents a small fraction of soil organic matter (OM), it is involved in many biogeochemical processes in the environment. Its composition reflects its sources of production, and the processes it has been exposed to. However, the processes taking place immediately after DOM production are still poorly understood, due to its high reactivity. In terrestrial environments, fresh leaf litter is one of the major initial sources of DOM, before it is degraded. This PhD focused on the characterisation of DOM produced by different vegetation species, and the evolution of their properties during biodegradation. The relationship between the composition of vegetation cover and the molecular signature of DOM has been assessed, in order to determine the influence of molecular signature of vegetation leachate on natural DOM composition in the environment.The water extractable OM (WEOM) produced by 6 vegetation species (C. stellaris, F. nivalis, E. vaginatum, B. nana, B. pubescens, and Salix sp.) were characterised through complementary analytical technics. The results showed that the quantity and composition of WEOM produced by vegetation were different between plant functional types (PFT). It was also pointed out that some proxies commonly used to characterise DOM were not relevant to the study of unprocessed WEOM. However, the comparison of relevant proxies indicated that graminoids were potentially less biodegradable than lichens, but more than shrubs. WEOM biodegradation experiments were carried out under controlled conditions. For this purpose, 4 species belonging to different PFT were selected, and their WEOM extracted. These species were C. stellaris (lichen), E. vaginatum (sedge), A. polifolia (dwarf evergreen shrub), and B. nana (deciduous dwarf shrub). The results showed a significantly higher consumption of WEOM produced by C. stellaris and E. vaginatum, than A. polifolia and B. nana, at the end of the experiment. In the meantime, the accumulation of recalcitrant compounds in ...