Rocky Mountains (Canada, USA)

A characteristic feature of the treeline in many parts of the Rocky Mts. is the formation of tree islands and clonal sprouts emerging from low-lying branches. The treelines in the lee and luv of the Sierra Nevada of California are exposed to extremely different snow pack: The western parts receive so much winter precipitation that snow pack extends into July in many places. The eastern dry parts host one of the world's oldest trees: the treeline forming bristle cone pine (Pinus aristata). Although most of their trunks are dead, strip bark of younger age maintains a live - though fragmented - crown. The old age of dead structures results from the dry, cold climate.

1 - Abies lasiocarpa and Picea engelmannii, Medicine Bow Mountains, 3300 m (a)

2 - Pinus flexilis, Picea engelmannii, Abies lasiocarpa, Niwot Ridge, 3400 m (a)

3 - Pinus contortia, Abies lasiocarpa, Picea engelmannii. Banff National Park, 2200 m (b)

4 - Pinus contortia, Abies lasiocarpa, Picea engelmannii. Banff National Park, 2200 m (b)

3, 4 - Pinus contortia, Abies lasiocarpa, Picea engelmannii. Banff National Park, 2200 m (b)

5 - Mixed conifer forest near Saddleback Lake, Tioga pass, Sierra Nevada, California (c)

6 - White Mountains of California, 3550 m (c)

7 - Pinus aristata ("bristle cone pine"), 2000-3000 years old (c)

8 - Pinus aristata ("bristle cone pine"), 2000-3000 years old (c)

7, 8 - Pinus aristata ("bristle cone pine"), 2000-3000 years old (c)