Résumé
Despite its importance for human activities, soil biodiversity remains largely unknown. This gap of knowledge is a strong limit for studies including it such as in the agricultural field. Particularly, in France, no large-scale monitoring of soil biodiversity exist for the moment except for microorganisms (bacteria and fungi). Aware to this need, with the support of OFB, we studied the feasibility to add a soil biodiversity survey (RMQS-Biodiversity) to the already existing French soil quality monitoring network (RMQS). It is a systemic monitoring based on a 16*16 km grid where the sampling is done on a plot at the center of the mesh, which could belong to different land use types (forest, crops, urban gardens and wastelands, vines, orchards, pastures, meadows and other natural habitats). The sampling occurs throughout the year, every 15 years since 2000. The advantages to lean the new survey on an already existing one compared to establish an independent survey are that 1) field teams are already operational, 2) it reduces costs and 3) different data types (in our case, with pedologic and management practices ones) can be crossed at the country scale with a high statistical power to infer spatial and temporal variations and drivers. The objective of this new monitoring is to cover almost the whole soil biodiversity. With this aim, we gathered experts on soil microflora, microfauna, mesofauna and macrofauna and soil functions. We ask them if the RMQS sampling strategy could fit with a soil biodiversity survey. We together choose the taxons and functions to be surveyed, the associated protocols and estimate the related financial, material and human needs. According to the experts, the sampling design of RMQS fits with a soil biodiversity survey. We select sampling protocols for i) bacteria and fungi, ii) protists, iii) nematodes, iv) mesofauna (particularly springtails), v) below-ground macrofauna (earthworms), vi) surface macrofauna (beetles and spiders), and considering functions, vii) soil porosity, viii) enzymatic activity and ix) organic matter degradation. Before starting at National scale, we tested on several sites the selected sampling protocols and various sampling strategies in order to optimize the temporal sequence, the spatial arrangement of the protocols, the time spent on the field and to reduce the effect of disturbances on the soil organisms. The RMQS-biodiversity is a promising project that will help to fill the knowledge gap of soil biodiversity in France. The data would be used to assess the distribution of soil organisms and monitor the changes in soil biodiversity at the scale of the French territory. In addition, coupling data provided by biodiversity survey with data from RMQS will allow deciphering links between biodiversity, physical-chemical characteristics of the soil and human activities (practices, heavy metal loading, and pesticide residues for instance). Moreover, the RMQS-Biodiversity could serve as a model for other countries to establish a large-scale integrative soil monitoring including both pedologic and biodiversity data.