One green roof type, one Technosol, one ecological community

Green infrastructures play a key role in the functionality and resilience of urban ecosystems. The physical, including thickness, chemical and biological properties of the Technosols of green infrastructures on rooftops are highly variable, leading to more or less favourable conditions for soil biodiversity. The aim of this study was to investigate the abundance and diversity of bacteria, fungi, nematodes, collembola and plants communities in relation with abiotic parameters of Technosols on 12 productive and extensive green roofs of the Paris region (France). Results showed that green roofs harboured a high level of abundance and diversity from microorganisms to micro and mesofauna. Microbial biomass ranged between 16.3 and 419.8 mu g DNA g-1, with a predominance of bacteria, nematodes represented 820-60,700 individuals per kg of soil and between 1000 and 60,700 collembolan were present per m2 of soil. A total of 13,986 bacterial OTU (Operational Taxonomic Unit), 33,559 fungal OTU, 47 Collembola species, 28 nematodes families, 16 cultivated plant species and 48 spontaneous plant species was identified on all the green roofs studied. Microbial, animals and plants communities were significantly different between the two types of green roofs. Productive and extensive rooftops represent contrasted habitats, which can strongly influence the soil biota. Any voluntary action to enhance soil biodiversity in cities would need to take-into-account both soil properties and the landscape around.