Research Unit : UMR-1137 Ecologie et Ecophysiologie Forestières (EEF) (Centre Inra de Nancy-Lorraine, Université de Lorraine)

Supervisors of the PhD thesis :
Jean Luc DUPOUEY, Directeur de Recherches, Inra, UMR UMR-1137 Ecologie et Ecophysiologie Forestières ; [email protected];
Sandrine CHAUCHARD, Maitre de Conférences, Université de Lorraine, UMR UMR-1137 Ecologie et Ecophysiologie Forestières ; [email protected];
Vincent BADEAU, Ingénieur de recherches Inra, UMR UMR-1137 Ecologie et Ecophysiologie Forestières ; [email protected]

General aims and state of the art :
The Jurassic limestone plateaus in Northeast France (from Longwy (north) to Dijon (south)) are deeply carved by several wide river valleys (e.g. Moselle, Marne, Meuse, Armençon, Yonne) but also by numerous steep-sided valleys. These peculiar landforms, often parts of wide and homogeneous forest areas, have long been identified as specific and rare habitats, of high environmental value (Le Tacon & Timbal, 1972; Bugnon et al., 1974; Rameau & Timbal, 1979). According to the variability of their orientation, length, width, depth, hydrography and sinuosity these steepsided valleys are characterised by a diversity of small-scale microclimates (Scherrer and Körner 2011) which differ greatly from the regional climate and the surrounding plateau, with greater thermal and moisture amplitudes (at a daily or annual time step; Le Tacon & Timbal 1972). If the south-facing slopes are much warmer and characterized by
a sub-mediterranean climate, north-facing slopes and thalwegs are colder, wetter and characterized by a submontane climate. Consequently, each steep-sided valley of the Jurassic limestone plateaus exhibits large variation of climate at fine-scale (below 100m scale) «Cold valleys» constitute thus a microrefugia – e.g. small areas with local favourable environmental features in which small populations can survive outside their core distribution area (Rull, 2009) – for both cold-adapted and thermophilous species.
Presence of these restricted microclimate leads to the occurrence of specific plant species (thermophilous species on south-facing slope e.g. Quercus pubescens, cold-adapted species in the thalweg and on the north-facing slope, e.g. Aconitum lycoctonum or Cardamine heptaphylla) and habitats (Bugnon & Rameau 1974, Noirfalise 1960, Timbal 1977). Species and habitats of “cold valleys” are in sharp decline for several reasons: presence of forest tracks in the thalwegs, changing hydrology due to management, substitution of native deciduous forest species by coniferous plantations, strong logging on steep slopes leading to soil erosion or at the other extreme decrease of forest management leading to a canopy closure and the disappearance of the heliophilous species (such as the very rare Cypripedium calceolus, for example). Climate change poses a new threat to these ecosystems but it has never been evaluated. Since the coldadapted plant species located in the north-facing slopes and thalwegs of the “cold valleys” are already located at their lower altitudinal range, a temperature increase could have strong negative impacts on their distribution and then lead to change in species distribution and then communities composition. On the opposite,
thermophilous species located in the south-facing slopes should benefit from temperature increase and their range should expand. Then, in a context of anthropogenic warming, “cold valleys”, as microrefugia might i) continue or not to provide suitable habitat for some cold-adapted species, ii) provide suitable habitat for new threatened species (mesic species) and mitigate the extend of the biotic extinction (Rull, 2009) and iii) play a role in subsequent range expansion notably for thermophilous species located in the south-facing slope (Hylander et al, 2015). “Cold valleys” should contribute to mitigate climate change effect as their microclimates are decoupled from the regional climate. Their present and future roles depend on the degree and the persistence of decoupling. Indeed, portion of the sites with strong decoupling to regional conditions have a greater potential to persist through time (Dobrowski, 2010). Microrefugia, notably warm-stage microrefugia, have been the subject of recent studies and syntheses in mountain environment, notably in the Alps (Patsiou et al. 2014, Gentili et al 2015) but none was conducted in lowlands whereas climate change velocity should be much higher in flat landscapes (Loarie et al. 2009). Moreover, sites that support microrefugia most often differed for cold and warm stage (Dobrowski 2010). “Cold valleys” offer both kinds of microrefugia in close vicinity: warm-stage microrefugia for cold-adapted species in the thalweg and the north-facing slopes, and cold-stage microrefugia for thermophilous species on the south-facing slopes. Thus, “cold valleys” offer the opportunity to study the different roles of microrefugia in a lowland landscape: i.e. conservation of cold-adapted species and source for range expansion of thermophilous species.

Specific research questions :
Although the flora of “cold valleys” has been surveyed in the past, a synthesis of this documentation, often published in grey literature, is needed to consolidate our knowledge on the vegetation, soil and climate of these peculiar environments. This will help, on one hand, building a relevant knowledge basis to model the present (and then through times) distribution of these habitats and their specialized species and, on the other hand, identifying and protecting the most typical sites. This synthesis could help managers of protected areas, as Natura 2000 sites, to identify conservation values of site and prioritize conservation actions in an anthropogenic warming context.
Due to the high level of decoupling of the local and micro-climates of such “cold valleys” compared to the regional climate, they represent ideal and appropriate case studies for challenging and refining species and community distribution models that use climate and high-resolution topoclimatic predictors. Commonly used species or community distribution models that use only general climate parameters as predictors often show poor accuracy.
Several studies have shown the relevance of using high-resolution topographic predictors to refine species distribution models (Lassueur et al. 2006, Pradervand et al. 2013, Leempoel et al. 2015). In particular, cold valleys could help in addressing the following questions: (1) are high-resolution topo-climatic predictors sufficient to detect the presence of such topographic features and to adequately predict the distribution of specialized species or vegetation
units? (2) can new-developed predictors (slope, aspect, solar radiation, particular topographic features), selected to be proxies for processes occurring in cold valleys, improve the predictions of distribution models?
The main objectives of the project are:
i) Improving our knowledge on location of “cold valleys” in order to help protect the most typical plant species and communities;
ii) Characterising the vegetation and the local and micro climate of “cold valleys” as a function of their topographic attributes;
iii) Understanding mechanistically the climatic basis of “cold valleys” with climate sensors to ultimately refine topo-climate predictors used in species and community distribution models;
iv) Evaluating the temporal dynamics of climate and vegetation of cold valleys with the combination of databases, empirical models and in situ measurements by sensors.

Innovation and impact for the society :
This thesis will enhance our knowledge on “cold valleys” (notably their spatial distribution), enhance knowledge of vegetation-microclimate relationship, and, more generally, on the way species can or cannot move and survive in the long term in landscapes under climate change. It will help improve the adequacy of our decisions concerning the identification and the protection of the specific habitats which could act as refugia in the near future and therefore have a high environmental value. Several public agencies in France are directly interested in the results of this project: DREALs, Conservatory of natural sites, General council, Forest National Office.

Available equipment / experimental support / associated research projects :
Floristic informations on species occurrences (Lorraine’s and Burgundy’s limestone plateaus) have been previously collected: 416 floristic inventories (mainly collected in the 1970s, 1980s) were compiled from ancient literature and SOPHY database and classified to offer habitat/communities characterization. The knowledge of such a list of species should allow a more efficient search for relevant ancient vegetation surveys in other, complementary databases (e.g. National Forest Institute database, regional databases). The teams have access to and expertise on the main environmental and forest vegetation databases at the French and European levels.
The availability and intensity of sunlight (solar radiation) can be calculated with computational routines developed by the team for ArcMap or R, using the digital terrain model of the IGN at a 25m resolution. Topographical features can estimate the cold air pooling, e.g. topographic amplification factor and local concavities/convexities of the terrain, as used by the Lausanne University team. The team owns about 30 temperatures/humidity sensors that will be used for field measures.

Skills that the doctoral fellow will gain during the contract :
Integrative modelling starting from the cambium, to the whole tree within a stand.
Biomechanical modelling needs to combine different kinds of models dealing with structural mechanics, tree growth, mechanobiology especially about perception and responses.
3D morphometry from different sources (X-Ray, T-Lidar)
Forestry experiment (definition and management of protocoles)
General knowledge about forestry, tree development and grading of roundwood.

Applications :

Applicants to this contract should send the application files including:
1. A detailed CV with all details about obtained degrees, fulfilled training and results;
2. A motivation letter (2 pp) indicating the selected topic, a description of the skills of the candidate with respect to the topic and the plans of the candidate for his/her future career;
3. Two recommendation letters provided by professors or researchers who supervised the candidate during his/her training.
4. Whenever possible, a copy of the degrees obtained up to now.

You should hold a Master’s degree in life sciences or environmental sciences with an excellent grade list. You should demonstrate an interest in transdisciplinary research. You are expected to be creative and open-minded and to have the ability to establish and maintain good interpersonal relationships. Knowledge of French language is not a prerequisite. You should demosntrate a good level of spoken and written English, and the thesis may be written in English.
The research will mostly take place at the Inra campus, Champenoux (30 min by bus) or at the Faculté des Sciences et Techniques, Université de Lorraine, Nancy. The research groups are all members of the “Laboratoire d’Excellence” ARBRE (http://mycor.nancy.inra.fr/ARBRE/). In these groups, you will benefit from the support of advanced technical platforms devoted to genomics, stable isotopes, electronic and confocal microscopy, wood science, etc… You will be member of a large-scale research community of about 350 persons working in forest and wood sciences (see http://www.nancy.inra.fr/).
Nancy is a medium-sized city (350000 inhabitants including suburbs) located in North-Eastern France. The city is very attractive in terms of gastronomy, cultural activities, architecture (ranging from the UNESCO classified Place Stanislas (18th century) to the so-called ‘Ecole de Nancy’ style),….The countryside is very peaceful with lakes and many forests, close proximity to the Vosges mountains (for skiing, trekking, mountain biking…), to Belgium, Luxembourg and Germany. There is very easy access to Paris (1h30 to Paris with the high speed TGV train) and to other destinations in France and the continent (30 min from National Airport Nancy-Metz, 1h15 from Luxembourg International Airport).
Applications files should be sent to the administration of the Doctoral School ([email protected]) with a copy to the president of INRA Centre de de Recherches Grand Est-Nancy ([email protected]) not later than Friday May 19th 2017. We recommend that you have a brief exchange with the scientist responsible for each topic before applying.