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Maréchaux Isabelle

DEEP

PhD

Icone contact Email


PhD project


Individual-based modelling of tropical forests :
role of biodiversity and responses to
drought

 


Supervisor

Jérôme Chave

Context

Amazonian forests are critical for providing, supporting and regulating global ecosystem services. However, empirical evidence for their vulnerability to climate change has been accumulating over the past decade. For example, the 2005 and 2010 Amazonian droughts led to a decrease in tree growth and an increase in tree mortality, and such droughts have been predicted to increase in frequency and intensity. It is thus critical to better understand and model tropical forests dynamics and responses to perturbations. 
Until now, the diversity of species and their interactions and responses to environment has been poorly accounted in vegetation models such as Dynamic Global Vegetation Models. By ignoring species and functional diversity, models may fail to describe features of vegetation structure or dynamics, such as productivity, biomass or stability. Jointly model elemental cycles and the dynamics of biodiversity is a highly demanded research program, to help increase model predictive power in a context of global changes, improve our understanding of ecological systems and communities, and develop robust management and conservation planning.

Objectives
 
The broad aim of my PhD project is to analyze and model a tropical forest dynamics, taking into account the wide functional and species diversity that these ecosystems shelter. During this 3-year project, I used two main approaches that feed each other, modeling and ecophysiology.
 
In a first part of my PhD, I aimed at developing a spatially-explicit and individual-based model of tropical forests. This work is based on a model initially developed by Jérôme Chave. We integrate recent advances in plant physiological community processes modeling, and we relate these processes to species-specific functional traits in a parameterization for a tropical rainforest, taking advantage of large plant trait databases.
 
Considering the lack on information on tropical tree drought tolerance that hinders the development of a relevant representation of tropical forest community responses to drought in vegetation models, in another part of my PhD, I aimed at documenting and quantifying the physiological drought tolerance of Amazonian trees and its diversity. This work benefits from great collaboration with Megan Bartlett and Lawren Sack (UCLA), funds from the LabEx CEBA and field work at the Nouragues station, French Guiana. You could find here a little home-made 8-min movie about one of our field session.



Publications

Maréchaux I. & Chave J. (in press). An individual-based forest model to jointly simulate carbon and tree diversity in Amazonia: description and applications. Ecological Monographs.

Tymen B., Vincent G., Courtois E.A., Heurtebize J., Dauzat J., Maréchaux I., Chave J. (2017) Quantifying micro-environmental variation in tropical rainforest understory at landscape scale using high-resolution airborne LiDAR and a distributed sensor network. Annals of Forest Science 74:32.

Maréchaux I., Bartlett M., Iribar A., Sack L., Chave J. (2017). Stronger seasonal adjustment in leaf turgor loss point in lianas than trees in an Amazonian forest. Biology Letters 13:20160819.

Maréchaux I., Rodrigues A.S.L., Charpentier A. (2016). The value of coarse species range maps to inform local biodiversity conservation in a global context. Ecography.

Maréchaux I., Bartlett M., Gaucher P., Sack L., Chave J. (2016). Causes of variation in leaf-level drought tolerance within an Amazonian forest. Journal of Plant Hydraulics 3:e004.

Maréchaux, I., Bartlett, M. K., Sack, L., Baraloto, C., Engel, J., Joetzjer, E., Chave, J. (2015). Drought tolerance as predicted by leaf water potential at turgor loss point varies strongly across species within an Amazonian forest. Functional Ecology 29:1268-1277.

A podcast interview about this study is available on the website of Functional Ecology or at this link.


Previous projects

In 2012, I worked with Ana Rodrigues and Anne Charpentier at the CEFE-CNRS, in Montpellier, France. We explored the following topic :
"From thinking globally to acting locally, how to make the best use of limited available biodiversity data in identifying priorities for conservation ?"

In 2013, I worked with Florent Taberlet from the WWF-Guyane, French Guiana and Audrey Coreau from AgroParisTech, Paris, France. With a social science approach (using the framework of Strategic Environmental Management), we explored the following topic :
"Guyanese forests adaptation to climate change : who can act and why ? From the emergence of an environmental issue to its place on the agenda."
More information on this project is available here and here.



About me

Before my PhD, I made undergraduate studies in mathematics and physics, at Ecole Polytechnique, near Paris, France, and then passed a master degree in ecology, evolution and conservation sciences in Paris, France (Paris VI-ENS-AgroParisTech-MNHN).