Western Mediterranean formations of small or medium Cistus spp., most characteristic of the siliceous soils of the meso-Mediterranean zone, but also widely occurring in the thermo-Mediterranean zone and in the siliceous supra-Mediterranean zone. Formations dominated by different Cistus species are included as subunits, with the exception of: formations of mostly calciphile Cistus species (e.g. Cistus albidus, Cistus clusii) and of indifferent species accompanied by strongly calciphile floras are classified as unit F6.1; formations of entirely thermo-Mediterranean species (e.g. Cistus bourgaeanus, Cistus palhinhae, Cistus heterophyllus) and of widespread species associated with co-dominant thermo-Mediterranean species are classified as unit F5.5.