Résumé
To meet the challenge of the sustainable city, a better knowledge of the ecology of urban ecosystems is essential, with a major issue linked to the biological quality of soils in connection with land use and management practices. Improving the weak knowledge of soil biodiversity is indeed essential to tackle soil multifunctionality associated to urban greening. The Bises project (Biodiversity of urban soils and sustainable cities), deployed in four French cities with contrasting biopedoclimatic and historical situations (Montpellier, Nancy, Nantes and Paris), aims to understand the links between soil quality, soil biodiversity and the associated ecosystem functions and services. All the major families of organisms (macro, meso, microfauna and microorganisms) will be evaluated spatially in order to develop and aggregated indicators of the biological quality of urban soils. A multi-scale sampling strategy was implemented in order to select 48 sites per city representative of the use of urban vegetated space for ornamental (parks, road sides), or food production (family and shared gardens, urban micro-farms). Lawn-type plant cover was selected for non-productive spaces to ensure homogeneity. Close collaboration with city services enabled accessing to spatial mapping of vegetated areas in cities. The selection of site location for each type of use integrates parameters such as site area, position along the urban-rural gradient (from city center to periurban areas), age and history of site, management method for non-productive spaces (prestige=regular mowing, irrigation, fertilisation; rustic = one or two mowings per year) and type of valorisation of agricultural products (sales vs. not sales)