Team : MEA

PhD student :  MARTELLI Andrea

Thesis supervisors :  CHARRIER Guillaume , Saulnier Mélanie, Robin Marie-Hélène

Associated teams : GEODE (CNRS), EI PURPAN, AGIR (INRAe)

Dates : April 2025 - January 2028

Description

Increasing numbers of tree diebacks are being observed in forestry and arboricultural sectors around the world, causing serious concern. These complex phenomena, caused by multiple biotic and abiotic factors, are becoming more pronounced in the context of climate change and manifest themselves through observable or unobservable symptoms, which can lead to premature tree death. In an attempt to better understand the complexity of the mechanisms involved, and to analyse and identify how biotic and abiotic factors can combine and interact with climate change, this thesis proposes to develop models for predicting these risks of decline by combining scientific disciplines that were previously separate. The overall objective of the thesis, through the study of forest and fruit nut and chestnut systems, will be (1) to design a new digital tool that will enable the best possible identification of the main factors leading to the decline of chestnut and walnut trees, (2) to provide appropriate solutions for the design of sustainable and innovative systems, (3) to optimise forestry and arboricultural management, and (4) to better manage tree renewal. This new decision support tool (DST) will combine two complementary types of models: the Bioclimsol quantitative model (developed by the Centre National de la Propriété Forestière (CNPF), which offers a method for assessing the risks of decline and ecological incompatibility of forest species according to different contexts and climate change scenarios. The tool has benefited from the support of numerous institutional partners in the forestry and timber industry since 2009 and is gaining increasing scientific recognition. and IPSIM modelling (‘Injury Profile SIMulator’, developed by INRAE in Toulouse, which has broken new ground by offering a qualitative representation of the effects of cultivation practices, soil climate and the environment of the plot on a damage profile due to a set of pests (Aubertot and Robin, 2013; Robin et al., 2013)). This thesis thus proposes an innovative holistic approach to building a predictive tool that integrates: the abiotic compartment (soil-climate-plot link), the biotic compartment (plant material-pests-diseases) and potential anthropogenic factors (pruning-irrigation-management, etc.) by combining these two models, which will complement each other depending on the circumstances and plots. The tool developed will provide a completely new support for the forestry and fruit sectors for plot diagnostics, which is all the more important in these times of climate uncertainty and the need to adapt cultivation and forestry management practices.

The general objective of the thesis will be broken down into three research questions:

1. What are the links between the technical system, the soil climate and decline? Can the production performance of chestnut and walnut orchards be maintained in view of the increased risk of decline linked to climate change?

2. How do the symptoms of decline manifest themselves in different production situations (all the physical, chemical and biological characteristics of a plot and its environment), and according to the socio-economic and technical factors likely to influence the manager's decisions?

3. How does the decision support tool for simulating dieback risks contribute to a participatory approach to designing innovative systems? What new decision rules can be developed?