Study area. a: Location of Rome Municipality (red circle) within the Italian territory. Latium Regioni is in black. b: Location of the study area (in green) within the Rome Municipality (red line). GRA is the Grande Raccordo Anulare, a motorway conventionally used to define the urban area of Rome. S.L. = Sealing Layer. c: Land use categories occurring in the study area. Numbers indicate location of sampling sites, numbered according to the urban-rural gradient.