DRF: Thesis subject SL-DRF-21-0817
toward a new modeling approach of vegetation dynamics to better understand evolution of past climate and there interactions with climate
In the 2000s we have seen the emergence of Dynamics General Vegetation Models (DGVM) which dynamically simulate the evolution of plant functional types (PFT) as a function of climate change. These models made it possible to understand how vegetation could influence climate by reducing or, on the contrary, amplifying climate change and are especially very useful for study of paleo climates. DGVMs simulate vegetation and soil functioning (carbon, energy water..) and the land cover evolution related to change of the climate However, if theses models have largely improved there simulation of vegetation functioning, the simulation of land cover dynamics remains crudely model and has almost no changed for past 20 years, leading to a high degree of uncertainty in the types of vegetation simulated. The current approach in DGVM, if it takes into account for competition between functional types thru plant productivity stay mainly driven by a statistical and simple description of the climate envelope where vegetation can survive. However, approaches developed at the species level such as the PHENOFIT model (Chuine et al 2011) make it possible to explicitly represent what is called fitness, which is the ability of an ecosystem to survive and reproduce instead of just considering observed climate envelope of the ecosystems. The objective of the thesis will be to develop a new modelling conceptual framework that combine detailed approach of vegetation fitness as represented in PHENOFIT (http://capsis.cirad.fr/capsis/help_en/phenofit) with detailed representation of vegetation functioning of DGVMs using in one of leading model in the world, ORCHIDEE (https: / /orchidee.ipsl.fr/). The first stage of the Phd will be to develop the new modelling approach combining PHENOFIT and ORCHIDEE. In particular it will require to see how to extend the PHENOFIT approach initially developed at species level to the more general concept of plant functional type. For second stage of the Phd, once the approach has been developed, it will be used to simulate the vegetation dynamics over key past periods, such as the Middle Holocene, the Last Glacial Maximum, but also the climatic transitions such as those associated with the abrupt climatic events of the last ice age and its end. Simulation will be done on GENCI/CEA HPC resources. As it require complex modelling tools and data analysis, the applicant should have a good skill in computing tools and a background on ecophysiology would be a added value. The work will be carried out at LSCE, one of the world’s leading laboratory on climate study with a close collaboration with Isabelle Chuine from French academy of Sciences. The Phd will benefit from a large community of people working on the ORCHIDEE DGVM and expertise on HPC at LSCE. I will allow the applicant to acquire a good multidisciplinary expertise on climate science, ecophysiology and modelling of complex systems and HPC.
Start date of the thesis: 01/10/2021
Sciences de l’Environnement d’Île de France
LSCE CE Orme des Merisiers 91191 Gif sur Yvette Cedex