Tropical grassy biomes (TGB), the world’s ancient savannas and grasslands, support outstanding biodiversity, and provide key ecosystem processes. Our goal is to understand the functional mechanisms promoting the restoration of native herbaceous TGB communities that are fire-resilient, self-sustaining, invasion-resistant, and able to provide crucial ecosystem processes. We choose the Cerrado (Brazilian savanna) as a model to answer our research questions as it hosts a vast biodiversity, offers many ecosystem services and is currently highly threatened. We will set up a Biodiversity-and-Ecosystem-Functioning field experiment to understand how the manipulation of both functional diversity and species richness of herbaceous plants allow the establishment of a continuous herbaceous ground cover. We aim at better understanding how functional diversity and species richness modulate restored ecosystem functioning. Current restoration of Cerrado herbaceous communities rely on direct seeding of fast-growing, acquisitive species, whereas we will develop methods that allow establishing a range of species, including species with conservative strategies, characteristics of pristine TGB. Yr1: collect seeds and propagules from 4 functional groups; set up field experiment. Yr2-4: monitor vegetation (establishment, plant functional traits, invasive species, flammability) and ecosystem processes (erosion control, productivity, carbon and water cycles). Test, in mesocosms, if the response of the functional groups to invasive species is modified by extreme weather events. Yr3: set prescribed fires. Yr4: monitor recovery. We expect to find a positive correlation between the complementarity of functional traits and restoration effectiveness. This project will contribute to deepening TGB ecological knowledge and to informing guidelines for effective TGB restoration. Partnerships with stakeholders and local traditional Kalunga communities should improve these guidelines.

Forests are a major reservoir of biodiversity and trees, as keystone organisms, directly impact the diversity and functioning of forest communities. Predicting the response of trees to ongoing global change (GC) is thus a critical scientific and societal issue. Along with phenotypic plasticity and migration, genetic adaptation is a central component of this response, particularly in trees whose high levels of diversity and long distance gene flow facilitates the spread of favorable genes. However, the existence of abundant genetic variation does not guarantee adaptation: if the climate and environmental changes are too quick, or genetic modifications are too slow, the population would go extinct before it can adapt to the new environmental challenges. Our hypothesis is that there is a critical level of genetic diversity for stress responses, which, together with the demographic impact of stress, predicts the likelihood of adaptation or extinction. The main goal of TipTree is to identify tipping points in the demographic and micro-evolutionary dynamics of tree populations, and to assess how human actions interfere in the adjustment between the rate of evolution and the velocity of GC. TipTree benefits from the BiodivERsA project LinkTree (2009-2012) which investigates the evolutionary response of key forest tree species to GC by analyzing the spatial variation of stress tolerance candidate genes along environmental gradients. But TipTree brings a new and critical dimension, that of time, by focusing on regeneration. In trees, regeneration (from fertilization to early plant recruitment) is a key period of the life cycle, when selection is expected to be very strong and has the potential to catalyze the rapid spread of evolutionary novelties in the next generation. The amount of genetic variation available in adults and how it is transmitted, selected and expressed in juveniles will condition the ecological properties of the whole ecosystem in the next decades to centuries, which remains a challenging short and non-equilibrium term of evolution for long-lived organisms. Specifically, our consortium will: 1) Screen the ecological and geographical margins of widespread keystone forest trees from different ecoregions (Temperate, Boreal, Mediterranean and Tropical) to identify where recent environmental changes have provoked shifts in allele frequencies at adaptive genes and to quantify these shifts by contrasting parent and offspring genetic and phenotypic compositions. We will address key environmental drivers: water stress, temperature regime, storm/fire frequency, pest outbreaks. Using natural and controlled (reciprocal transplants, common gardens) populations from existing Pan-European networks, we will generate large arrays of genomic polymorphisms using innovative genomic approaches, 2) Test the existence and evaluate the magnitude of tipping points for tree population dynamics at micro-evolutionary scales, by using a new generation of models coupling biophysics, population dynamics and quantitative genetics. We will feed these models with (i) climate change scenarios provided by IPCC, (ii) forest management scenarios established by our stakeholder group and (iii) our experimental results on adaptive genetic diversity. Micro-evolution of tree populations will be simulated at local and regional scales, and will provide forecasts of ecosystem services (carbon budget and water balance) and decision support for management.

Trees play an essential role in the functioning of urban socio-ecosystems, providing vital ecosystem services for city dwellers. The diversity, size and distribution of trees in urban spaces reflect the socio-cultural dynamics of cities. Urban trees are vulnerable to environmental stresses and, as such, are sentinels of global change (heat, drought, soil artificialisation, erosion of biodiversity, introduction of species) as much as they represent a management lever for adapting cities to climate change. Understanding the factors that make urban trees vulnerable to biotic and abiotic stresses is essential if we are to manage the urban forest and sustainably drive the ecosystem services provided by trees to city dwellers. As the majority of urban trees are privately owned, urban forest management initiatives need to be a joint effort between municipal services and private individuals. This implies that all stakeholders share the same knowledge of the matter, the different management options and their consequences. It is therefore essential that scientific knowledge about turban tree health is accessible, understood and shared between the great diversity of stakeholders and citizen. OSCAR - the Scientific and Citizen Observatory of Urban Trees Hetalth - has this threefold ambition: (1) to co-construct scientific knowledge through the sponsorship of sentinel trees, (2) to encourage the dissemination of this knowledge in various forms so that (3) it can be appropriated by individuals and managers of green spaces and urban forests.

In the face of climate change, we need to understand the drivers of changes in forest composition. Functional traits hold great promise as a way to explore and depict how the interplay of species climate stress tolerance and competition drives these changes. To date, progress has, however, been limited because we have a poor understanding of how traits control tree demography. DECLIC will build on the increasing availability of forest inventory data documenting tree demography and the emergence of key physiological traits directly linked to survival to determine how those traits control tree demography response to drought, frost, and competition in Europe and North America. This will allow us to develop size-structured community assembly models predicting forests dynamics along climatic gradients based on species traits. These models will be used to derive metrics of forest vulnerability to climate change such as evaluations of the risk of forest dieback, productivity decline and regeneration impeding at the scale of French ‘sylvoécoregions’. Then we will co-construct with French forest managers the best approach to present these metrics and their uncertainty on a web-platform adapted to disseminate them broadly.

The WUEtree project focuses on "water use efficiency (WUE)" and the functional related traits because the challenge of many tree plantation programs, facing the global changes, is to improve the tree adaptation and the biomass production without increasing water extraction. The project responds to BIOADAPT in developing research on adaptation mechanisms and is situated at the interface of the two themes proposed by the call: “biological adaptive response of living organisms facing global change” and “methods and selection tools to adapt organisms to global changes”. WUEtree tests the general hypothesis that WUE exhibits significant variability within tree population and that it can be improved in breeding programs without compromising the biomass production. WUEtree aims at understanding the biological basis of WUE and its genetic and environmental determinisms. The ultimate goal is to define an ideotype and a selection methodology combining phenotypic and molecular information. To reach this objective we develop with a 36 month research program, through four scientific tasks (tasks 2 to 5) and one coordination and management task (task 1). The task 2 consists in understanding the functional relationship between WUE measured at leaf level (WI) and tree level (Wp) with ?13C and other related ecophysiological components (leaf traits, transpiration, etc..). It seeks to predict WUE at leaf and individual tree level using ?13C and related traits. The task 3 estimates the genetic and environmental variance components of ?13C and related traits and the correlations with biomass using quantitative genetic models. The task 4 is complementary to task 3 and seeks to understand, using association studies and fine mapping strategy, which genomic regions and which genes underlie ?13C and associated traits. In task3 and task 4 the genotype by environment interaction is evaluated using appropriate field designs showing different stress levels. The task 5 uses tasks 2, 3 and 4 information to test selection methodologies, such as genomic selection, associating both phenotypic and genomic data. The objective is to provide new statistical models to accurately rank genotypes. WUEtree is conducted with two tree model species, the hybrid Eucalyptus urophylla x grandis and Pinus pinaster, and relies on original experimental field trials established respectively, in the Republic of the Congo and in the south west of France. The expected results are a better understanding of the biological basis of WUE and of the genetic and environmental determinants. This new knowledge will be used for defining and selecting ideotypes presenting optimal WUE and productivity for marginal zones. The four partners, UMR 1134 AGAP CIRAD-INRA-SUPAGRO “genetic improvement and adaptation of tropical and Mediterranean plants”, its sub-contractor CRDPI “Centre de Recherche sur la Durabilité et la Productivité des Plantations Industrielles, Republic of the Congo”, UMR1137 EEF INRA-Université de Lorraine "Ecologie et Ecophysiologie Forestières”, UMR 111 Eco&Sols Montpellier SupAgro–CIRAD–INRA–IRD “Ecologie Fonctionnelle & Biogéochimie des Sols & Agroécosystèmes” and UMR 1202 BIOGECO INRA-Université de Bordeaux 1 “Biodiversité Gènes et Communautés” exhibit strong complementary skills combining genetics and biostatistics (AGAP/BIOGECO), tree ecophysiology (EEF/BIOGECO), process-based modelling (Eco&Sols/EEF), tree genomics and genome analyses (AGAP/BIOGECO) and field trial management (CRDPI/BIOGECO). The position of AGAP, Eco&sols and of BIOGECO in institutions associating research and companies involved in tree plantations (“Eucalyptus Fiber of the Congo” with the CRDPI), (GIS “Pin maritime du Futur” consortium funded by its memberships (INRA, FCBA, CRPF, CPFA and ONF), offers opportunities for the project to significantly impact the Eucalyptus and maritime pine breeding programmes.