The Notre-Dame de Paris (NDP) wooden oak frame is one of the greatest masterpieces of Gothic carpentry in France. It was constructed during the High Middle Ages (HMA) between the 11th and 13th centuries, at a time of profound environmental and societal changes – climate optimum, strong demographic and economic growth – which created significant pressure on available forest resources, one of the key economic drivers of medieval societies. The destruction of the NDP wood framework in the fire of 15 April 2019 left thousands of charred and fragmented oak wood pieces. Analyzing this "forest" means to almost go back in time, by rebuilding the forests of past centuries and restoring this heritage for the public. The CASIMODO project aims to understand the impact of climatic and anthropogenic factors on the evolution of the HMA forest–wood socio-ecosystem: forest, raw wood material management, and manufactured end products in the Île-de-France and Paris Basin. The project proposes three lines of research to address society’s adaptive response to the availability of wood resources during the HMA. The first purpose is to define the climatic and the socio-economical context of Paris. In order to identify the potential technical adaptations of the medieval society, the second objective is to study the timber and destroyed framework from an archaeological point of view in order to characterize the construction supply methods of the building site. The third purpose consists of characterizing the forest stands exploited in the 11th–13th c., their management, and the possible silvicultural systems used for the production of adequate timber. The overall goal of CASIMODO is to provide crucial information and enable a fuller understanding of the evolution of an economic area under climatic, societal and demographic pressure, through the wood life cycle. We propose to develop an integrated approach by combining history, archaeology and bioarchaeology. Trees record variations in environmental variables, with each annual growth ring containing a means of dating, and a set of anatomical and chemical markers indicators providing information of the woodland structure, the geographical origin of the wood, and past climate. This information will be compared with contemporaneous wood data from secular and religious medieval frames from Northern France, Southern Belgium and Western Germany. Complementary proxies, such as textual archives and paleoenvironmental/bioarchaeological data of medieval archaeological sites in the Île-de-France and Paris Basin will also be integrated. By echoing the context of the current ecological threat, this project addresses recurring problems in human–nature relations and is in line with the theme of societies facing environmental change. Improved documentation of temporal and spatial variability in past global climates is needed to better anticipate the possible impacts of future climate change. CASIMODO can provide indirect clues on the extent of deforestation or even natural disasters and linked epidemics such as the plague. In addition, radiocarbone dating is a central tool of modern science (biology, ecology, geology, history, archaeology.); however, it is still hampered by the imprecision of dates obtained for certain periods. Progress in this direction will, therefore, be a major step forward for very large section of the scientific community

Forest are complex social-ecological systems that deliver many contributions to humans and other species. Yet, like most ecosystems on Earth, French forests are increasingly impacted by on-going climate change, which alters their structure, biodiversity and functioning and threatens their renewal. Their sensitivity, and by extension the sensitivity of their contributions, is expected to increase in the next decades. At the same time, there is an increasing demand for the decarbonization of the economy, with a strong demand for forest products and services. As a result, forests are now facing a key challenge: how promoting their ability of carbon sequestration without impacting the other contributions to people, while taking into account their vulnerability to climate change? FISSA will bring elements to answer this question, by simulating forest’s contributions according to Sustainable Development Goals (SDGs), under both climate change and management scenarios. More precisely, FISSA will aim at assessing the effect of different forest management scenarios and several climate scenarios on forests contributions, and analyzing trade-offs and synergies between contributions within a socio-ecological framework. In FISSA we will thus test how the regionalization of the different forest management changes the balance between the vulnerability to climate change impacts and its mitigation, how the level of management intensification could also threaten other forest contributions to people, and whether tree diversity may improve the resilience of forests socio-ecosystems and their contributions to climate change mitigation and adaptation. To do so, FISSA will rely on the close interaction between the outcomes of sociological analyses and cutting-edge forest models simulations, to provide insights at both local and national levels. First, we will analyze the expectations of the various actors of forest social-ecological systems and consider how they may influence the orientations of forest policies, to establish relevant forest management scenarios and strategies at national and local levels to be used in models simulations (WP1). FISSA will actually focus on three complementary spatial scales: pilot-sites, secondary sites, and national level. Second, we will couple complementary process-based models of forest dynamics and functioning to obtain a tool to provide predictions of forest composition and structure, forest productivity and health, and soil carbon storage. (WP2) at the scale of France and for a set of local sites for which particular stakes are identified in WP1. Third, we will predict how different climate change and management scenarios will affect forest contributions, with a special focus on carbon sequestration (WP3). Simulation outputs will be analyzed under the socio-ecological angle within the framework of the United Nations’ SDGs as well as national policies. They will then be shared with the actors to collect their perceptions and expectations, and – if needed – lead to a revision of management scenarios (WP3). Targeting both basic scientific questions and key applied-science issues, FISSA will benefit from a strong multidisciplinary consortium, including both scientific and non-academic partners, with strong potential for transfer actions. This project will tackle issues corresponding to a strong demand by public policies in Europe and in France, as well as key applied-science issues with strong link to socio-economic and cultural fields. Therefore FISSA aims at disseminating as largely as possible its results, especially to decision-makers and forest actors.

What will temperate forests be like in 100 years? And beyond? Can we or do we need to manage forest to adapt to climate change? These are pressing questions given that forests represent one of the most important ecosystems on Earth, being both a biodiversity hotspot and an important carbon sink of the Earth System. In France alone, forests cover around 31% of the surface and are under management pressure to satisfy environmental quality and wood demands. This is particularly true for European lowland temperate deciduous forest characterized by species such as Fagus sylvatica, Quercus robur or Quercus petraea. These species may attain high economic value constitute around 67% of the forest surface in France. Furthermore, LTF ecological importance is highly valued, as exemplified by a recent designation of the first national park in the lowland forests in France. The future persistence of these forests is, however, not granted within the next 100 years. Climate change is expected to drastically increase temperature thus intensifying droughts, and this will affect the survival of these important tree species. Bioclimatic model forecasts predict a substitution of LTF tree species by drier adapted species such as Q. pubescens and Q. ilex. Recent microclimate modeling suggests that canopy cover may buffer the increases in free air temperature, which could enhance the recruitment of LTF species under the canopy. In addition, the stress gradient hypothesis posits that under harsher conditions we may shift from plant competition with plant facilitation. These shifts are in contrast with current management strategies to enhance forest recruitment via increasing light availability and control of competition. Surprisingly, we have a lack of knowledge of the performance and plant-plant interactions of early life stages of trees along strong climatic gradient, which precludes the assessment of future forest regeneration and the stability of LTF forests. In SEEDFOR we combine seed experiments, microclimate sensors and advanced computational techniques to understand early life stages of LTF trees under climate-change dry conditions, and project the future of lowland temperate forests in France. First, we will plant several tree seeds in different climate conditions, using seeds from different provenances. We will then understand whether there are seeds and juveniles that may be more adapted to dryer conditions than others. Second, we will use a network of intense monitoring plots to compare the climatic potential for the establishment of a young tree versus the real establishment observed in forests. We will then identify whether climate is an actual constraint for new trees to recruit, or other factors (e.g. seed predation or herbivory) are the main constraint. Finally, we will build scenarios of forest management in a forest landscape simulation model. These will provide key information on harvest potential and whether to plant climate change adapted seeds. This information will help provide answers to our main challenge: Will we be able conserve temperate forest in a warmer world?

Forest management is currently disturbed by major contemporary crises (climate, biodiversity, relocalization and globalization, bioeconomy, etc.) that challeng silvicultural practices (Achim et al. 2022, Le Bouler 2021). All forest management operators are expressing a need for innovation supported by scientific knowledge, with one priority: adaptation to climate change. In this context, UMR SILVA is developing interdisciplinary research on the functioning and management of forests faced with the challenges of global change. To meet the specific needs of small private forests, NEOSYLVA INVESTISSEMENT FORESTIER (NIF) offers services for restoring management in small private forests, with an innovative business model based on a partnership between owner, manager and investors. The NEOSILVA joint laboratory between NIF and UMR Silva aims to set up R&D adapted to the management of small private forests (less than 25 ha) facing the multiple challenges of sustainable management threatened by climate change. These small forests are currently finding it difficult to enter R&D projects and networks, which are not tailored to their needs. NEOSILVA aims to back up NIF's innovative business model with a methodology for implementing innovative silviculture, highly sustainable in terms of both environmental services and wood production, adapted to the expectations and capacities of private forest owners and managers, and designed using scientific approaches. The deliverable is a multi-criteria decision support system, covering the three stages of management: diagnosis prior to handing over to management, definition of silvicultural trajectories, monitoring of operations and forest dynamics during the management plan, in the framework of adaptive and learning management. The joint laboratory's work program is based on UMR SILVA's Forest' Inn Lab group research on innovation systems. This research applies scientific and reflexive methodologies derived from the theories of open and user-centered innovation "livinglab" to build the deliverable. This research will then stimulate an interdisciplinary approach within UMR SILVA, with all its scientific expertise in pedology, ecology, ecophysiology, silviculture, forest growth simulation and ecosystem service evaluation, to co-design the various components of the multi-criteria decision support tool, based on the needs of forest managers. This process of co-construction between actors with different knowledge and points of view is the main element of the research and is analyzed as a research object. The program is being developed in two areas (one in the Western and one in the Eastern France) of very different forestry histories and cultures, to support the genericity of the deliverable and its interest as a scientific production. At the end of the project, the partnership will continue this research on open and user-centered innovation applied to forest management, but it will also amplify the transfer to management of the latest advances in research in ecology, silviculture and other forest sciences, with a better understanding of the needs of stakeholders. In the longer term, it will lead to joint R&D in silviculture based on the monitoring of long-term experiments (over 10 years), which should be included in the In-SYLVA France national research infrastructure.

In the context of climate change, forests will face more frequent and intense periods of water deficit. How forests react to this climatic stress will depend, to a large extent, on their access to the soil water resource. For a long time, the so-called “available water content” (AWC, in millimeters of water) has been identified as a key ecosystem parameter, modulating the forest response to water shortage. Yet, AWC is typically determined over shallow depths (e.g. 1-m), and does not consider that in many cases, trees can access deep water resources, the depth and quantity of which is currently not known. Recent works developed by our consortium have introduced the concept of Total Available Water (TAW) to trees, a concept that adds “deep water” to the AWC estimate. Deployed at scales from the forest site to Metropolitan France and supported by an interdisciplinary consortium, the TAW-tree project aims (1) to quantify the TAW reserve in forests through a combination of geophysical (WP1) and ecophysiological (WP2) approaches, (2) to upscale TAW at regional scale using remote sensing (WP3) in order to (3) quantify the influence of TAW on the functioning, growth and vulnerability of temperate and Mediterranean forests facing climate change (WP4). Our working hypotheses are (hypothesis 1) that AWC generally underestimates TAW, often in a considerable way in forests, (hypothesis 2) that the variations of TAW in a particular forest drive a large part of the inter-tree differences in their response to water shortage, (hypothesis 3) that TAW, and particularly its deep component, has a critical role in the functioning and vulnerability of forests exposed to heat and drought stresses and that it changes the forests’ contribution to groundwater discharge.