Modeling of the boreal vegetation and its dynamics in the ORCHIDEE continental land surface scheme

• Main Author: Druel, Arsène
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Université Grenoble Alpes, Gerhard Krinner, Philippe Peylin
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2017
• Subjects: Shrubs - Mosses - Lichens; Land-Surface model; Orchidee; Boreal vegetation; Vegetation dynamics; Climate modeling; Buissons - Mousses - Lichen; Modèle continental; Végétation boréale; Modélisation climatique; Dynamique de végétation; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Arctic; albedo; Arctic Greening
• Online Access: https://tel.archives-ouvertes.fr/tel-01654663; https://tel.archives-ouvertes.fr/tel-01654663/document; https://tel.archives-ouvertes.fr/tel-01654663/file/DRUEL_2017_diffusion.pdf

Climate evolution over the next ten to hundred years involves many questions, linked to the impact of man. Indeed, greenhouse gases emissions since the beginning of the industrial era lead to an increase in temperature. The latter can affect terrestrial ecosystems, particularly in boreal regions where observed and projected temperature increase is larger than in mid-latitudes. Evolution of these ecosystems can trigger climate feedbacks. For example, the currently observed « Arctic greening » phenomenon could enhance the warming via a decrease in albedo due to the increase in vegetation cover. In order to address these questions, climate models were developped, including continental surface models taking into account the fluxes of mass and energy. In this thesis, such a model was used, the continental surface scheme ORCHIDEE, which includes a succinct description of boreal vegetation. The aim of this work was thus the implementation and the modeling of boreal vegetation.In order to describe high-latitude vegetation, i.e. toundras and steppes, new plant functional types (PFTs) were integrated into the model based on existing PFTs. First, non-vascular plants (NVPs) were integrated to represent lichens and bryophytes found in desert toundras and peatlands, then shrubs to represent an intermediate stratum between trees and grasses in toundras, and finally boreal C3 grasses to distinguish vegetation found in boreal steppes and temperate grasslands. The description of this boreal vegetation was accompanied by the integration of new charachteristic processes, from the implementation of new interactions such as the protection of shrubs by snow in winter, to the simple choice of new PFT parameters such as the lower photosynthetic capacity of boreal C3 grasses compared to temperate C3 grasses, through the modification of existing processes such as the stomatal conductance of NVPs. Other processes linked to vegetation were also updated or corrected. Finally, to model the dynamics of boreal vegetation, new PFTs were ...