sentences:  More frequently than in pure concentrations, it is found mixed with cork oaks and Holm oaks.The most characteristic natural pine forests are those of "pino negro" ("Pinus uncinata") and Scots pine ("Pinus sylvestris").The former is often associated with "Rhododendron ferrugineum", blueberries, "Salix pyrenaica" and other shrubby species on the subalpine slopes of the Pyrenees.