StemFlore : un programme national de suivi temporel de la flore vasculaire française. Plan d'échantillonnage, protocole terrain et méthode d'analyse FRESCALO. Version 2

Monitoring changes in biodiversity is a major challenge in this era of global change. National botanical conservatories have long been responsible for conducting general inventories of vascular flora, with the aim of establishing species distribution atlases for their respective territories. The resulting data constitute a fundamental knowledge base, providing crucial insights into various policies for the conservation of plant biodiversity. The FRESCALO method facilitates the utilisation of such datasets for the evaluation of temporal trends in species frequency, through the implementation of corrections for the heterogeneity of sampling pressures experienced across both space and time. Nonetheless, preliminary analyses have underscored the necessity for the structuring of inventories, with a view to ensuring the reliability of temporal trends that are obtained. The network of CBN is planning to deploy a vascular flora monitoring system called STEMFLORE, with a unified sampling strategy and protocol at the national level. The system is based on a 5 x 5 km grid and aims to achieve a spatially balanced distribution of the grids to be sampled in order to analyse variations in species frequency over six-year intervals. Grid sampling is stratified according to biogeographical areas and altitudinal gradient, as well as seasons. The selection of samples within the grid is stratified according to the type of habitats present within it. The protocol delineates between mandatory points, which are indispensable for the purpose of temporal monitoring or other central objectives, and recommendations, which permit greater versatility in the data acquired. The proposal of three sampling pressure scenarios is intended to facilitate adaptation to the available resources and the capacity of each CBN to deploy the system. Further work is required to reinforce specific aspects of the sampling plan, the protocol, and the utilisation of this dataset for the generation of temporal trend indicators with FRESCALO.