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Reproductive traits of oak trees: what future under climate change ?

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General information

Reference : UMR5558-SAMVEN-001
Date of publication : Friday, July 26, 2019
Scientific Responsible name : Samuel Venner
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 November 2019
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

In many perennial plant species, the intensity of fruiting is extremely variable from year to year and synchronized at the population level. Oak species (Quercus sp.) are emblematic of these reproduction strategies called masting (Koenig and Knops, 2013, Schermer et al. 2019) and oak masting represents a major ecological and economic challenge. While large interannual fluctuations in acorn production are crucial for the reproduction of tree individuals, population recruitment and forest regeneration, they also have a significant impact on the demography and evolution of the animal species consuming this resource (mammals, birds, insects) and, in cascade, on community dynamics and the functioning of forest ecosystems as a whole (Ostfeld & Keesing 2000, Yang et al. 2010). Deciphering the still poorly understood mechanisms of oak masting and its efficiency in controlling the demographics of fruit consumers is necessary to predict the consequences of climate change on the dynamics of fruiting, the dynamics of the communities that depend on it and that of the forest ecosystem.
The first objective of the thesis will aim to determine the proximal causes of masting in temperate oaks by identifying the rules for allocating resources in flowering and fruiting as well as the meteorological conditions that may interfere with pollination, fertilization and/or fruit ripening. The second objective of the thesis will be to develop a new version of a mechanistic model of masting (Schermer et al., 2019) and a "plant-insects" co-evolution model that will evaluate the efficiency of masting in controlling the dynamics of acorn parasitic insect communities and the consequences of masting on oak reproductive success and regeneration success in oak forests. The third objective of the thesis will be to develop projections of oak masting and oak regeneration in the context of climate change.
Objective 1 will be based on the analysis of data already available, data collected on 150 trees spread over 15 sites in metropolitan France and monitored since 2012. Objectives 2 and 3 will be based on the development of a new version of the mechanistic masting model (Schermer et al., 2019) to be coupled with an evolutionary dynamics model of acorn insect communities already initiated in LBBE. The climate projections used will be those produced as part of the EURO-CORDEX initiative (Kotlarski et al., 2014).
References :
Kelly, D . & Sork, V.L. 2002. Mast seeding in perennial plants : Why, How, Where ? Annu. Rev. Ecol. Syst. 33: 427–47.
Koenig, W. D. and J. M. H. Knops. 2013. Large scale spatial synchrony and cross-synchrony in acorn production by two California oaks. Ecology 94: 83-93.
Kotlarski, K., Keuler, K., Christensen, O.B., Colette, A., Déqué, M., Gobiet, A., Goergen, K., Jacob, D., Lüthi, D., van Meijgaard, Nikulin, E.G., Schär, C., Teichmann, C., Vautard, R., Warrach-Sagi, K. & Wulfmeyer, V. 2014. Regional climate modeling on European scales: a joint standard evaluation of the EURO-CORDEX RCM ensemble. Geosci. Model Dev., 7, 1297–1333, 2014
Ostfeld, R.S. & Keesing, F. 2000. Pulsed resources and community dynamics of consumers in terrestrial ecosystems. Trends Ecol. Evol. 15 : 232-237.
Schermer, E., Bel-Venner, M.C., Fouchet, D., Siberchicot, A., Boulanger, V., Caignard, T., Thibaudon, M., Oliver, G., Nicolas, M., Gaillard, J.M., Delzon, S. & Venner, S. 2019. Pollen limitation as a main driver of fruiting dynamics in oak populations. Ecol. Lett., 22: 98–107.
Yang, L.H., Edwards, K.F., Byrnes, J.E., Bastow, J.L., Wright, A .N. & Spence, K.O. 2010. A meta‐analysis of resource pulse–consumer interactions. Ecol. Monographs, 80, 125-151.

Work Context

The thesis will take place in the quantitative and evolutionary ecology team of the biometrics laboratory of Evolutionary Biology (LBBE, It will be funded by the ANR FOREPRO (beginning on 1/11/19, led by S. Venner) which will aim to understand the mechanisms of masting oaks from the Mediterranean and temperate regions, its ecological consequences and its future in the context of climate change. The thesis will be directed by Samuel Venner and Marie-Claude Venner, specialists in both acorn insect parasites and masting. In addition to the supervising team, the thesis work will benefit from collaborations with various scientists and managers with complementary skills: Sylvain Delzon (BioGeCo, UMR INRA, Univ Bordeaux); Isabelle Chuine (CEFE, Montpelliers), Nicolas Delpierre (ESE, Paris-Sud), Aurélie Siberchicot (LBBE, Lyon) and Vincent Boulanger (ONF, Fontainebleau).

Constraints and risks

The thesis work will be based mainly on data analysis and the development of mathematical/informatics models, which will require internal training for the optimal use of the computing resources made available by the LBBE. Participation in field sampling (15 days per year) is envisaged and will require compliance with the safety rules for missions in forest environments (weather risk assessment, reporting the mission to forest officers, telephone contact at the beginning and end of the mission).

Additional Information

The candidate must hold a master's degree in ecology/evolution research obtained in 2018 or 2019. The position requires strong knowledge of statistical analysis, modelling and computer programming, good oral and written communication skills (French and English required) to present at conferences and write articles in scientific journals. Applications must include a detailed CV, at least two referees (who may be contacted), a one-page cover letter, Master 2 notes). The deadline for sending applications is 25/08/2019.

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