Training period for Master student
4 months April-July or May-August 2018
UMR Biogeco, INRA Bordeaux, France
Desired candidate profile: master in ecology or forestry / engineer in forestry; basic knowledge in biology, ecology, data analysis, GIS
Dynamics of Robinia pseudoacacia
In recent decades, there has been an increased concern about exotic tree invasions (Richardson & Rejmánek 2011). Most species were introduced for economic reasons (e.g. forestry, landscaping) but showed severe economic and environmental impacts when they have become invasive. Invasive trees are suitable models to understand general invasion patterns and processes (Richardson & Pyšek 2006).
There are eight dominant hypotheses proposed to profile factors involved in invasion success. They focus either on community or ecosystem-level properties that relate to susceptibility to invasion (invasibility, Williamson 1996; Lonsdale 1999) or on species life traits that promote successful colonization of exotics (invasiveness, Williamson and Fitter 1996). One of these hypothesis is referred to as the propagule pressure hypothesis (Williamson and Fitter 1996; Lonsdale 1999): for instance, some exotic grass and tree species have been found to produce high numbers of seeds promoting their invasion, thus largely spreading in many habitats and ecosystems. Another process implied in invasiveness is related to phenotypic plasticity – i.e. the change in plant traits in response to changes in the environment – that would play an important role in invasions, in particular, in the initial establishment.
The project focuses on black locust (Robinia pseudoacacia), ranked among the 100 most problematic invasive species in Europe. Native to North America, it was deliberately introduced into Europe (1601) for ornamental and production purposes. Given the properties of the wood, it is subject to a breeding program in the center of Europe, is subsidized by the state in plantation forests, but its wide invasiveness poses environmental problems to the natural area managers: it is typically a conflicting use tree (Dickie et al 2014).
Black locust reproduces sexually by producing seeds, but is also capable of clonal reproduction: new stems can be produced by resprouting (stems at the base of the main stem) or root-sucking (stems emerging from the roots).
Our objective is to evaluate the degree and variability of resprouting ability among populations of Robinia pseudoacacia from the native American range, and from the invasive European range.
The project will pursue two tasks:
• An experiment will be set up where American and European seeds will be grown under optimal environmental conditions, and stems will be cut to follow the production of resprouts. Results will be analysed using mixed statistical models.
• At the regional scale, forest inventories data will be analysed to (1) evaluate the pattern of distribution of Robinia pseudoacacia in natural areas, (2) assess the relationship between these patterns, the environmental conditions (vegetation cover, soil, land use, road networks etc.) and the impact on local biodiversity. The analysis will require the use of GIS and spreadsheet softwares (ex. MS Excel).
This master project is part of the PhD project of Xavier Bouteiller, under supervision of Stéphanie Mariette and Annabel Porté. The candidate will be working as part of this team.
The candidate will learn ecophysiological techniques, data analyses methodologies, scientific reporting.
A monthly gratification is provided following the French regulation (around 500 euros per month).