The spruce-fir forest consists primarily of two conifer species—red spruce (Picea rubens) and Fraser fir (Abies fraseri). The Fraser Firs, which are native to Southern Appalachia, once dominated elevations above in the Great Smokies. Most of these firs were killed, however, by an infestation of the balsam wooly adelgid, which arrived in the Smokies in the early 1960s. Thus, red spruce is now the dominant species in the range's spruce-fir forest. Large stands of dead Fraser Firs remain atop Clingmans Dome and on the northwestern slopes of Old Black. While much of the red spruce stands in the Smokies were logged during World War I, the tree is still common throughout the range above . Some of the red spruce trees in the Smokies are believed to be 300 years old, and the tallest rise to over .