Leys Bérangère

Chercheuse CNRS / Researcher

Equipe Paléoenvironnement et Processus Macroécologique
UMR IMBE | Aix Marseille Université, CNRS, IRD, Avignon Université

Technopole Arbois Méditerranée - Batiment Villemin
av Louis Philibert 13545 Aix-en-Provence

Contact Berangère Leys


I am a long term ecologist, interested mostly by the fire ecology and its consequences on ecosystems. I am also a program coordinator for different projects.

I am currently Associate Editor of Journal of Ecology (2018-).

Research interests :

Disturbances such as fire and herbivory, are key factors acting on the functioning of terrestrial ecosystems. Better frame the impact of both repetition of a same disturbance, and the impact of multiple disturbances on an ecosystem is the key to break new ground in the comprehensive functioning of complex ecosystems. I am mostly interested now by the Mediterranean area which constitute a key lab of all extreme events and responses to biodiversity.
​This work is interdisciplinary, and I collaborate frequently with geologist and biogeographers to globally understand the impact of fire in different diversity indexes, and the couple action of multiple repeated disturbances. I also used to work with modelers and land managers to go further by integrating the current economical needs, and the future impacts on ecosystems.

Key-words : fire, herbivores, Mediterranean, charcoal, resilience, disturbance regime.

Experiences et parcours académique

Chercheur CNRS (Oct 2020-) – IMBE Institut Méditerranéen de la Biodiversité et de l’Environnement continentale et océanique
Aix-Marseille Université (Marseille, France).

Chef de projet (Mars-Sept 2020) – Institut Archimède Mathématiques Informatique
Aix-Marseille Université (Marseille, France). Dir E. Godard _ Assurer la mise en œuvre et le pilotage de projets structurants de l’institut.

Chercheur associé (2018-2019) – Ecologie des communautés en prairie
Chrono-environnement (Besançon, France). Avec Pr. F Gillet _ Sujet : Impact de la fertilisation des prairies sur leurs diversités taxonomique, fonctionnelle et phylogénétique

Chercheur associé (2017–2018) – Feu et réponses des savanes tempérées
Chrono-environnement (Besançon, France) _ Sujet : Fire, climate, and vegetation change in an oak savanna ecosystem from annual to millennial time scales.

Chercheur associé (2014-2017) – Perturbations et réponses des écosystèmes forestiers et prairiaux
Kansas State University (Kansas, USA) Avec K.K. McLauchlan _ Sujet : Biogeochemical consequences of ecosystem change at decadal to millennial timescales.

ATER (2013-2014) - Ecologie des communautés en milieu forestier
Centre d’Ecologie Fonctionnelle et Evolutive (Montpellier, France)
Avec I. Chuine et X. Morin _ Sujet : Distribution des espèces clés méditerranéennes et alpines en réponse au climat et autres contraintes environnementales (altitude, sol, compétition)

Doctorat en Ecologie (2012) – Biodiversité et écologie du feu en forêt méditerranéenne
Ecole Pratique des Hautes Etudes (Paris, France) - ISEM (Montpellier, France). Directeur : C. Carcaillet_ Sujet : Facteurs explicatifs de la dynamique des végétations au cours de l’Holocène en système méditerranéen et alpin : climat et perturbation feu.

Master 2 Environnement et gestion de la Biodiversité (2009)- Ecologie tropicale
Ecole Pratique des Hautes Etudes (Paris, France) - ISEM (Montpellier, France) Encadrants C. Favier et L. Bremond _ Sujet : Densité du couvert arboré tropical mesurée par la surface foliaire et enregistrée par les phytolithes.

Master 1 Biologie, géologie et communication scientifique (2008) –enseignement SVT
Université Paris 7 Denis Diderot _ Admission au concours du CAPES externe en Sciences et Vie de la Terre. _ Thèse didactique : La complexité de l’interrelation Professor-Etudiant. Dir : Pr. Tassel, Mme Skurnick.

Research projects

Fire impacts on biodiversity

The Mediterranean Basin is a world hotspot of biodiversity, in which small islands have become ultimate refugia for the exceptional flora and fauna. I aim to reveal the impact of fire on past vegetation dynamics and its interactions with grazing and human activities on several small islands. I’ll addresses four objectives : 1) quantifying the fire regime (area burnt, frequency, and intensity), 2) quantifying the historical herbivore density, the fuel type and fuel quantity, 3) identifying the long-term vegetation dynamics, i.e. composition, diversity, functional types, and landscape structure, and 4) Identifying ecosystem dynamics of Mediterranean small islands and the implications of the combined drivers effect for conservation.
The resilience of Mediterranean small island ecosystems – the capacity of these systems to return to the state before disturbances – will be evaluated for the Antiquity periods, from where changes in land uses were important and diverse, for the industrialization period, and for the intended management actions of the protected areas.
This unique interdisciplinary methodology will allow to pave the way for a better use of paleoecology lessons into ecosystem management on keystone islands.

JPEG - 210.7 ko

Biogeochemical impact of disturbances on ecosystems

Humans have been changing the Earth’s cycles by increasing atmospheric carbon dioxide and fertilizing with nitrogen, a limiting nutrient for forest productivity. With the enrichment of nitrogen, a paradigm of progression from N to phosphorous or calcium limitation has developed. ​In a short-term period, disturbances, notably fires are regulator of ecosystem processes such as nutrient or carbon cycles, but biogeochemical consequences are particularly difficult to quantify, especially over long time scale. Nonetheless understanding the interactions between climate, disturbances and biogeochemical cycles is crucial regarding the current and future global changes.

The challenge is to understand the impact of disturbance on volatile and nonvolatile nutrients and quantify the intake of these nutrients in lake sediments depending on the type of disturbance and its severity. The first goal is to define the threshold from which soil nutrient losses are significant enough to limit the productivity of the system and change the dynamics or the trajectory of the vegetation. The second goal is to quantify nutrient demands and dynamics of forested as well as non-forested ecosystems, notably temperate grasslands and Mediterranean areas, where fire frequency reconstructions are difficult if not impossible.

Grassland fires in a long-term perspective

​Grassland ecosystems represent 40% of the emerged lands but 80% of the fire activity took place in those systems each year. The estimated contribution on carbon release by savannah ecosystems only is currently around 40%, but more investigations are needed to quantify accurately the carbon emissions of all the grassland types. The fire regime in the past could have play a crucial role in the progressive increase of CO2 in the atmosphere, but the high frequency observed today is likely going to exacerbate this trend. A lack of concern over the impacts of environmental change on biodiversity in natural grasslands, and their importance in releasing carbon in the atmosphere persists in part because we currently lack a framework for conceptualizing the role grasslands, and because of the challenges in interpreting charcoal in sedimentary records to decipher the long-term dynamics of grassland systems.

The challenge is to cover the lack of fire histories in grassland systems to maintain this ecosystem containing a high biodiversity of plants and animals, including endangered species. The first goal is then to help fire history reconstruction in grassland ecosystems by calibrating charcoal record with fire parameters, and vegetation assemblages. The second goal is to reconstruct fire history in grasslands, and provided the natural fire regime experienced by these systems in order to manage them accordingly in the future.

Coordination and organization

par Berangere Leys

Program coordination

Program Coordinator of Archimedes Institute
Institute of Mathematics andComputer Sciences of Aix-Marseille University (2020) financed by Amidex Foundation.
Director : E. Godard, co-director : X. Roulleau and C. Capponi (300 000 € annual budget). 3 laboratories and about 300 faculty members, partnerships with Toulon University, Century institute and ILCB Institute, private businesses. Programs development and follow up for both research and teaching in Artificial Intelligence, Deep machine learning, Data sciences, Numerical sciences.

Assistant – coordinator of FindTIME project
“Fire, climate, and vegetation change in an oak savanna ecosystem from annual to millennial time scales” (2017-2019) financed by the National Science Foundation. Small Grant Ecosystem panel PI : K. McLauchlan, co-PI : D. Griffin, Senior Personnel : B. Leys, P. Reich, and S. Hobbie ($150 000). 28 faculty members, 5 different countries. Steering committee member, development and coordination of 2 work packages.

Assistant – coordinator of Novus Research Coordination Network
“Biogeochemical consequences of ecosystem change at decadal to millennial timescales.” (2014-2017) financed by the National Science Foundation Ecosystem panel. PI : K. Mclauchlan. 125 membres of 78 institutions from 15 countries. Membre of the steering committee, membre of the decisional committee, development of collaborations.

Scientific collaborations and leading skills
Collaboration with 12 European researchers from 8 different institutions, and 18 non-European researchers (Canada, and the United States) from 11 different institutions.
Collaborative work with biogeochemists, modellers, geologists, terrestrial ecosystem ecologists, denrochronologists, limnologists, or paleoecologists.
Close work with 4 institutions of land management : in France (National Office Forestry), in Italy (Forestry officers of Paneveggio protected area), and in the United States of America (Officers of Konza Prarie Biological Station, Hubbard Brook Ecosystem Sciences ; and Cedar Creek Ecosystem Science Reserve, all part of Long Term Ecological Research program).

Organisation skills

Novus workshop 4, at Hubbard Brook Experimental Forest, NH, USA (26-28 September 2017).
grants and diffusion of the workshop announcement in European and US networks ; Programme of the meetings ; chair man

Novus workshop 3, at Cedar Creek Ecosystem Science Reserve and at the University of Minnesota, MN, USA (15-22 May 2016)
Recon visit ; Preparation of the scientific facilities and collaborations ;
Diffusion of the workshop announcement in European and US networks ;
Application reviews to fund expenses of external researchers or early career scientists ;
Writing of a funding proposal in the Ecosystem panel of NSF (Small Grant – $150,000).

Paleoenvironment lab weekly meetings, at Kansas State University, KS, USA (Fall semester 2016)
Room reservation and preparation of the facilities ; Programme of the meetings ; Invitation of guest speakers.

Seminar for PhD students of Ecole Pratique des Hautes Etudes (EPHE), at Montpellier (11-12 April 2010)
Room reservation ; Snack and catering orders ;,Invitations of guest speakers and students ; Programme of the seminar.

Research skills

par Berangere Leys

Laboratory and fieldwork skills

Fieldwork skills : Lead field teams, lake, tree and soil coring, sediment sampling, plant macroremain identification, charcoal extraction and identification.
Data analyses : big data set, charcoals, plant macroremains, pollen, isotopes and elements.
Sedimentology : 210Pb, 137Cs, 14C techniques, loss-on-ignition, particle sizes, magnetic susceptibility, X-Ray techniques (fluorescence and diffraction).

Computer skills

Statistical tools : R software and packages and Matlab (MCAgeDepth and Charanalysis, SEA)
Analyses : test of significance (parametric and non parametric data), test of correlation, change point, linear model and linear mixed, random forest, cooccurrence network, multivariate (MFA, PCA, NMDS).
Models : LASS (Landscape Analysis and Simulation Shell software on R), ForClim (capsis 4 platform), Phenofit and PMP (Phenology Modelling Platform)
Specialized software : WindSeedle (image analyser for charcoal particles), HighPeak (XRD peak identification), CANOCO (multivariate analyses for pollen data, including DCCA), Tilia (plot pollen data).
Databases : user and/or contributor to the Global Charcoal Database, NEOTOMA, and NOAA databases.

Language skills

Fluent in French, English (written and spoken).

Peer-review articles and book chapter

21. Leys B., Nicod C., Manneville V., Letourneur C.,Bouton Y., Chemidlin Prevost-Boure N., Gillet F. (major revisions) Grassland diversity of mountain pastures in response to soil nutrient content, fertilization and cattle season load. Agricuture, Ecosystem and Environment

20. Heyer J., Brunelle A., Lundeen Z., Leys B., Rittenour T. Brewer S., Power M., (accepted) Sediment age control on the Dolores River Lake Bottom oxbow record in eastern Utah, USA. Quaternary International

19. Gauzere J. , Teuf B., Davi H., Chevin L.-M., Caignard T., Leys B., Delzon S., Ronce O., Chuine I. (2020) Where is the optimum ? Predicting the variation of selection along climatic gradients and the adaptive value of plasticity. A case study on tree phenology. Evolution Letters 4-2 : 109-123

18. Leys B., Griffin G., Larson R.E., and McLauchlan K.K. (2019) Century-scale fire dynamics in an ecotonal ecosystem. Fire 2, 51.

17. Nicod C., Leys B., Greffier B., Hennequin C., Ferrez Y., Gillet F. (2019) Diversities of the plant community and management impacts in grasslands through diagnostic species method Ecological indicators 107, 105584.

16. Leys B., Marlon J., Umbanhowar C., and Vannière B. (2018) Global fire history of grassland biomes. Ecology and Evolution, 8:8831–8852.

15. Leys B., Curt T., and Elkin C. (2018) Mosaic landscape pattern explained the vegetation resistance to high fire frequency in Mediterranean area over the last six millennia. International Journal of Earth Science and Geophysics, 4 : 017.

14. Belle S., Tonno I., Poska A., Musazzi S., Leys B., Lami A. (2018) Long-term effects of climate change on sources and pathways of organic carbon fuelling the benthic secondary production in small lakes. Freshwater Biology, 1:9.

13. Leys B., Commerford J.L., McLauchlan K.K. (2017) Reconstructing grassland fire history using sedimentary charcoal : considering count, size and shape. Plos ONE, 12 (4), e0176445.

12. Leys B., Higuera P, McLauchlan K.K. and Dunnette P (2016) Wildfires drive geochemical change in a subalpine forest over the past six millennia. Environmental Research Letters, 11 (12), 125003.

11. Leys B., Likens G. E., Johnson C. E., Craine J. M., Lacroix B. and McLauchlan K. K. (2016) Natural and anthropogenic drivers of calcium depletion in a northern forest during the last millennium. Proceedings of the National Academy of Science, 113(25), 6934-6938.

10. Leys B. and Carcaillet C. (2016) Subalpine fires in the Alps for the past 8000 years : the roles of vegetation, climate and, ultimately, land uses. Climatic Change, 135, 683-697.

9. Vannière B., Blarquez O., Rius D., Doyen E., Brücher T., Colombaroli D., Connor S., Feurdean A., Hickler T., Lemmen C., Leys B., Massa C. and Olofsson J. (2016) 7000-year human legacy of elevation-dependent European fire regimes. Quaternary Science Reviews 132, 206-212.

8. Commerford J., Leys B., Mueller J. and McLauchlan K. (2016) Great Plains vegetation dynamics in response to fire and drought episodes during the Holocene at Fox Lake, Minnesota, USA. The Holocene, 26 (2) 302-313.

7. Leys B., Brewer C.S., Mueller J., McConaghy S. and McLauchlan K.K. (2015) Fire history reconstruction in grassland ecosystems : charcoal amount reflects the local area burned. Environmental Research Letters, 10 (11), 114009.

6. Leys B., Carcaillet C., Blarquez O., Lami A., Musazzi S. and Trevisan R. (2014) Resistance of mixed subalpine forest to fire frequency changes : the ecological function of dwarf pine (Pinus mugo ssp. mugo). Quaternary Science Reviews, 90(0), 60-68.

5. Leys B., Finsinger W. and Carcaillet C. (2014) Historical range of fire frequency is not the Achilles’ heel of the Corsican black pine ecosystem. Journal of Ecology, 102(2), 381-395.

4. Leys B., Carcaillet C., Dezileau L., Ali A. A. and Bradshaw H.W.R. (2013) A comparison of charcoal measurements for reconstruction of Mediterranean paleo-fire frequency in the mountain of Corsica. Quaternary Research, 79, 337-349.

3. Blarquez O., Girardin M., Leys B., Ali A. A., Aleman J., Bergeron Y. and Carcaillet C. (2013) Reconstruction of paleo-fire based on an ensemble-member strategy applied to sedimentary charcoal. Geographical Research Letters, 40, 2667-2672.

2. Aleman J., Saint-Jean A., Leys B., Carcaillet C., Favier C. and Bremond L. (2013) Estimating phytolith influx in lake sediments. Quaternary Research, 80, 341-347.

1. Aleman J., Leys B., Apema R., Bentaleb I., Dubois M. A., Lamba B., Lebamba J., Martin C., Ngomanda A., Truc L., Yangakola J-M., Favier C. and Bremond L. (2012) Reconstructing savannah tree cover from pollen, phytoliths and stable carbon isotopes. Journal of Vegetation Science, 23, 187-197.

Chistopher Carcaillet et Bérangère Leys Une intime relation lie le feu et la forêt corse depuis plus de 11000 ans. Publié dans Feu et foret en Corse, ed. Stantari, 2012.

PhD thesis
Facteurs explicatifs de la dynamique des végétations au cours de l’Holocène en système montagnard méditerranéen et alpin : climat et perturbation feu. (Major driving force of vegetation dynamics in Alpine and Mediterranean mountain area during the Holocene : fire and climate) Supervisor Pr. Christopher Carcaillet. Delivered the 19 December 2012.

Conferences et colloquia

par Berangere Leys

Invited Colloquia

Centre Européen de Recherche et d’Enseignement en Géosciences et Environnement – 2019 (CEREGE, France). Fire is an enigmatic disturbance leading to both destruction and renewal of plant life. Climate and Environment Group.

University of Bern – 2017 (Bern, Switzerland). Consequences of nutrient availability on long-term vegetation dynamics. Institute of Plant Sciences.

Kansas State University – 2017 (Manhattan, KS, USA). Fire in grassland systems : millennial time scale of fire history reconstruction and consequences on nutrient cycling. Department of Biology, seminar in Ecology and Evolutionary Biology.

University of Oregon – 2016 (Eugene, OR, USA). Consequences of nutrient cycling on dynamics of vegetation at millennial time scale. Department of Geography, Environmental Change Research Group.

Kansas State University – 2015 (Manhattan, KS, USA). Use of handheld XRF and XRD techniques to assess long-term nutrient dynamics from lake sediment of Mirror Lake, NH. Department of Geology.

University of Utah - 2015 (Salt Lake City, UT, USA). Long-term fire ecology : processes and consequences on ecosystems. Department of Geography.

Centre of Functional and Evolutionary Ecology - 2014 (CEFE-CNRS, Montpellier, France). Alpine and Mediterranean paleo-fires : human- or climate-induced disturbance ?, Science Day of the Department of Functional Ecology.

Contributed conferences :

BES Festival of Ecology - 2020 (virtual) Leys B., Marlon J., Umbanhowar C., Vanniere B. Fire history of grassland biomes.

AGU - 2019 (San Fransisco, USA) Sayedi S., Abbott B.W., Vannière B., Leys B., Daniau A.-L., Colombaroli D., Gil Romera G., Słowiński M., Aleman J. C. Expert assessment of past and future changes in global fire regimes

SFE2 - 2018 (Rennes, France) Leys B., Marlon J., Umbanhowar C., Vanniere B. Fire history of grassland biomes.

Rencontres Archéobotaniques – 2018 (Besse-en-Chandesse, France) Leys B., Finsinger W., Carcaillet C. Les fortes fréquences de feux ne sont pas le point sensible du Pin noir, Laricio corse au cours des derniers 12 000 ans.

Past Global Changes (PAGES) Open Science Meeting – 2017 (Saragossa, Spain) Leys B., Higuera P., McLauchlan K.K., and Dunnette P. Wildfires and geochemical change in a subalpine forest over the past six millennia.

American Quaternary Association – 2016 (Santa Fe, New Mexico, USA) Leys B, Brewer C.S., Mueller J., McConaghy S., McLauchlan K.K., and Marlon J. Fire history reconstruction in Grassland ecosystems.

Ecological Society of America - 2015 (ESA, Baltimore, Maryland, USA, 2015) Leys B., Brewer S., Mueller J. McConaghy S. and McLauchlan K. Calibration of charcoal measurements for fire history reconstruction in grassland ecosystem.

European Palaeobotany and Palynology Conference - 2014 (EPPC, Padova, Italy) Leys B., Finsinger W. and Carcaillet C. Historical range of fire frequency is not the Achilles’ heel of the Corsican black pine ecosystem.

Models in Evolution and Ecology - 2014 (Montpellier, France, 2014) Leys B., Curt T and Elkin C. Impact of fire regime on Corsican black pine ecosystem : paleo-fire frequency reconstructed and fire behavior modeled.

FIREMAN UE project annual meeting - 2013 (Tallberg, Sweden) Leys, B. Impact of fire regime on Corsican black pine ecosystem during the Holocene : paleoecological and modeling approaches.

Tours 2012 - 2012 (Tours, France) Leys B., Finsinger W., Carcaillet C., 18,000 years of vegetation and fire history of Mediterranean mountain of Corsica (Lac de Creno), France.

Medpine 4 - 2011 (Avignon, France) Leys B., Carcaillet C., Long term fire and vegetation histories in Mediterranean mountain of Corsica, France.

Ecoveg 7 - 2011 (Lausanne, Switzerland) Leys B., Carcaillet C. Histoire des feux et de la biodiversité végétale méditerranéenne : étude d’un lac montagnard Corse.

GMPCA - 2009 (Montpellier, France) Leys B., Bremond L. et Favier C. Densité du couvert arboré tropical mesurée par l’indice foliaire et enregistrée par les phytolithes.

Teaching philosophy and mentoring

Teaching philosophy

My teaching philosophy emphasizes curiosity, interaction, acquisition of knowledge, application of that knowledge, and synthesis across multiple perspectives. My first concern as a teacher is to find the best way to spread my knowledge to future generations. I keep my lectures spontaneous and interactive while using day-to-day news, scientific debates, or problem based learning methods in my classrooms. My enthusiasm and outgoing approach to teaching allows me to naturally build a productive relationship with students, keeping them interested, attentive, and curious while learning fundamental and advanced concepts. I assess my students’ learning not only with homework and exam grades, but also improvement in critical thinking.

University of Utah (Salt Lake City, Utah, USA)
2017- 2020 PhD committee member of Joshua Paul Heyer
PhD title : A reconstruction of Dolores River watershed hydroclimate variability, a tributary to the Colorado River, using paleoecological, X-ray fluorescence, and watershed modelling techniques.
Supervised by Andrea Brunelle and Mitchel Power.

Kansas State University (Manhattan, Kansas, USA)
2015-2016 Mentoring of 4 undergraduate students, one Master student, and one PhD student. Projects related to grassland vegetation composition and fire history on the Holocene.
Undergraduated students : Training in charcoal extraction techniques from lacustrine sediments, and data acquisition by image analysis, weekly meetings and help with the writing of reports.
Master student (now Science Assistant at NSF) : Field protocol set up, training for the use and calibration of X-rays fluorescence for the elemental signature of soil, roc, plant and lacustrine sediment samples.
PhD student (now Associate Professor) : Training in the writing of scientific articles, including preparation of the manuscript, selection of statistical tests, presentation of results, preparation for submitting papers and response to reviewers.

Université Montpellier 2 (Montpellier, France)
2013-2014 Lecturer for undergraduate and graduate students
Geosciences class : Mediterranean environment, Biodiversity and crisis, Life history reconstruction, soil-organism interactions.
Biology class : Biodiversity and sustainable development, plant and animal biology, plant evolutionary, Functional ecology, human functions (nutrition, respiration…).
Other : professional development, CV and cover letter, seminars.

2009-2012 Teaching assistant
Geosciences class : Mediterranean environment, Biodiversity and crisis.
Biology class : Biodiversity and sustainable development, plant and animal biology, plant evolutionary, Functional ecology.

2011 Mentoring of 3 undergraduate students
Small independent research projects on ecological topics

2009 Creation and development of a course for undergrads : Biodiversity and Sustainable development (Lectures, fields, exercises and exams)

2006-2008 High School Buffon Paris, France ; High School Arsonval, and Secondary School Emile Zola, Choisy-le-roy, France