Methodology for phenoclimatic observations and modelling of Castanea sativa Mill. traditional cultivars and revitalizing chestnut growers’ local knowledge in France, ROC-CHA project

The ROC-CHA project is a joint project of researchers co-led by the CNRS (National Center for Scientific Research) and the SNPC (National Union of Chestnut Producers) in France. Our partners include INRAE Bordeaux, and associations involved in the development of chestnut cultivation in France, RENOVA in Ariège, Epi de Mains in Lozère, Groupement Régional des Producteurs et Transformateurs de Châtaignes et Marrons de Corse (GRPTCMC) in Corsica, as well as individual expert chestnut growers in Ardèche, Lozère, Corsica and Ariège and Agricultural Chambers (Ardèche and Corsica). This project aims at establishing a network for observation and conservation of chestnut cultivars at farm level and create synergies between scientific and chestnut grower’s local knowledge in France; with as main objectives to: 1) develop phenoclimatic observations and modelling of chestnut cultivars within the context of climate change, and 2) consolidate local knowledge and know-how of chestnut growers through peer-to-peer exchanges within a network of reference sites. These sites are on-farm living labs where we use a methodology developed by the “Observatoire des Saisons”, a research and citizen knowledge platform in France, that we refined and adapted through a co-construction process. Indeed, with some 20 chestnut growers, a practical approach for developing comparative observation of major phenological stages of chestnut cultivars development has been put together. The results presented in this paper are our methods for the follow-up of these phenological stages which are the budburst, initial opening of leaves, the flowering of first male flowers, the fruiting, and senescence, i.e., changes in leaf colouring and finally fallen leaves. All sites are associated to data loggers in order to obtain a database of temperatures, at the pace of one data per hour, 24 per day. We explain the approach that links researchers and chestnut growers, the observation processes, modelling and some preliminary results. We also present the experimental set up of peer-to-peer exchange of knowledge between chestnut growers, based on ethnoecological approaches for reconstructing fragmented local knowledge, the experimental setups that favour the emergence of almost lost knowledge, and we present some results regarding how this type of knowledge enables a better characterizing of numerous local varieties of these four regions. In conclusion, we consider that both, observation of phenological stages, and revitalizing local understanding of characteristics of chestnut cultivars, leads to a better understanding of how best to face climate change.