The EU Biodiversity Strategy 2020 aims to establish green infrastructures and to restore at least 15% of degraded ecosystems until 2020. In this strategy, forests play a key role since they provide multiple ecosystem services. European policy has invested great efforts in afforestation of former farmlands but has largely neglected opportunities for passive landscape restoration and defragmentation by spontaneous forest establishment (SFE). Yet, SFE is common in many parts of Europe due to the widespread abandonment of agricultural land use in past decades. SFE typically leads to many small forest patches that are not or little managed. Together with existing semi-natural forests, these new forest patches form a network of habitats that can help maintain biodiversity and ecosystem services. Although SFE may contribute to the creation of multifunctional, diverse landscapes, it has so far received little attention from ecological and social science research. In fact, SFE is often regarded as a challenge rather than an opportunity for landscape management and conservation. SPONFOREST will examine the potential of SFE as a cost-effective and politically feasible tool for reinforcing perennial green infrastructures of self-sustaining forests in fragmented landscapes. In-depth ecological and sociological studies will advance the understanding of forest regeneration in the landscape context, analyse ecosystem services and disservices of new forest patches and assess their perception by stakeholders and the greater public. Five case studies in Mediterranean and temperate landscapes will use this approach to investigate SFE under various environmental and socio-political conditions. The ecological research in SPONFOREST will analyse SFE with a broad spectrum of complementary approaches including dendroecology, population genetics, functional ecology, remote sensing, and landscape analysis. State-of-the-art field and laboratory methods will be used to gather high-quality data that inform a mechanistic framework aimed at forecasting SFE as a function of tree biology and the landscape context. The social science research of SPONFOREST will combine standardized surveys and in-depth expert interviews with stakeholders and policy makers to elucidate the societal perception of these new forests, their current use and the ecosystem services they supply from a demand perspective, including governance options to regulate this supply. SPONFOREST will place great emphasis on a detailed synthesis of the insights gained from ecological and sociological research, and will actively involve policy makers and experts in the transdisciplinary evaluation of key findings in view of policy recommendations. The comprehensive but distinct key deliverables address the scientific community, policy makers, forest and landscape managers. SPONFOREST should thus contribute to strategies that optimize future forest governance and management at local to European scales.

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.

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.

Parasites are able to evolve rapidly and overcome host defence mechanisms, but the molecular basis of this adaptation remains poorly understood. Identifying polymorphisms under selection in pathogenic fungal populations will help understanding the evolutionary processes underlying the adaptation to host-plant. Fungal genes may qualitatively determine whether a plant genotype can be infected or not (i.e. host specialization and/or virulence/avirulence) or may quantitatively determine the ability of the fungus to overcome the basal defence of the host plant species (i.e. aggressiveness). Recently, it has been proposed that the same molecular mechanisms could in fact underlie these seemingly different fungal traits. Taking advantage of the advance of Next Generation Sequencing technologies, GANDALF proposes to use a population genomics approach (i.e. without any a priori on the genes involved in host adaptation) for addressing the processes of adaptation in the ecological/agronomic gradient from host-plant specialization to quantitative adaptation to host-plant resistance. GANDALF is bringing together scientists from different laboratories and institutions having internationally recognized expertise in plant pathology, genomics, bioinformatics, evolutionary genetics and modelling (all ranked A by AERES, 4 being A+). Nine different pathosystems have been chosen, covering a large range of life history traits (e.g. biotophic vs necrotrophic, fungi vs oomycetes, etc.) and with genome sequences already available. Depending on the system, offspring of controlled crosses or natural populations will be analyzed. A first step aims at characterising strains for traits associated with host adaptation (phenotyping, Task 1). Re-sequencing of phenotyped strains will allow assembling, mapping and SNP discovery (Task 2). Genome-wide polymorphism data will be analysed following either a genome-wide association (Task 3) or a genome scan approach (Task 5). Since pathogens are prone to demographic and spatial variations, a method able to infer demographic parameters on populations will be developed in order to build a powerful tool of selection detection under complex population models (Task 4). Using this new tool, genome scan will be performed in order to detect loci under selection (Task 5). The candidate loci identified in tasks 3 and 5 will be validated by further genotyping on natural populations or collections available in laboratories. The genetic bases of host adaptation will be compared among fungal species and along the host specialization / cultivar specificity / aggressiveness continuum. This project not only will bring new insights into the understanding of genomic basis of fungal plant pathogens, but also will contribute to maintain the scientific excellence of the GANDALF partners by accelerating the integration of NGS technologies into their research program.

Forest canopies buffer climate extremes in the understory. This buffering capacity is key to explain understory biodiversity and forest regeneration, and thus forest resilience to climate change. It is also important for recreational activities. Forest management practices impact these ecosystem services by modifying forest structure and composition, and thus understory microclimate. Today, however, forest managers have no tool to quantify the impact of their practices on understory microclimate, notably in terms of climate extremes or under future climate conditions. The objective of MaCCMic is to develop such tools that will help identify the main factors influencing forest understory microclimate and anticipate the impact of forest management (density, fragmentation, thinning, choice of species, understory removal, etc.) and climate change on forest microclimate and understory vegetation, notably in terms of climate extremes. Bringing together long-term datasets of understory microclimate, state-of-the-art LiDAR and Sentinel2 products and biophysical forest microclimate modelling, we will quantify how understory microclimate is modified by local factors (canopy closure but also forest structure and functional diversity), landscape features (topography, but also the proximity of a river or the degree of fragmentation of the surroundings) and climate change (notably increasing atmospheric CO2 and its effect on plant physiology and forest regeneration). To best tease apart the different factors influencing understory microclimate, we will integrate existing and comprehensive datasets of forest microclimate from Europe, North America and the Neotropical region, but will also design specific experiments or use biophysical microclimate models. Results from the project will then be synthetized and translated into clear recommendations and easy-to-use tools to help foresters understand the impact of climate change and their practices on understory microclimate. For example, our results should help us write an expertise report on the impact of forest management on the understory microclimate in riparian forest corridors. Two web tools dedicated to forest owners and managers, but also the general public, will be also developed: (1) an interactive virtual forest that will show how forest management can influence understory microclimate during specific past and future extreme events and; (2) a web “tracker” that will summarise, based on near real-time data, how understorey microclimate is buffered and decoupled from its macroclimate, for a set of typologies of forests or tree plantations in a given region. Other expected outcomes of the project are: new teaching materials (for forest engineering schools or master programmes, but also middle schools), new microclimate datasets, software updates and technical notes, as well as 8 master reports, 3 PhD theses and several peer-reviewed articles. The results of MaCCMic will be closely followed by the community of terrestrial ecologists interested in how climate change impacts forest biodiversity. These results should also strongly interest the global carbon cycle and climate change research community, by bringing new understanding of the biophysical and ecological mechanisms of forest regeneration and resilience under rising atmospheric CO2 concentrations. Our results on the impact of understory microclimate and atmospheric CO2 increase on forest regeneration and resilience should also interest strongly the research community working on the global carbon cycle and climate change. Finally, MaCCMic should have a strong impact on the forest sector by providing new tools to help forest managers increase the resilience of forests and foster their ecological, recreational and climate services in a warming world.