Shoots were collected from various-aged Great Basin bristlecone pine trees (Pinuslongaeva D.K. Bailey) at three locations to determine whether shoot growth, stem unit production, and stem unit length decreased with increasing tree age. Trees from a southern Utah site were 14–2052 years old, whereas those from two White Mountains, California, locations were 824–4712 years old. Variation in shoot length, stem unit production, and stem unit length were not significant when regressed on tree age (r2 = 0.010–0.237). The fact that shoots from older trees showed no sign of reduced growth when compared with those from younger trees suggests that diminishment of annual shoot increment is not a definitive sign of aging in Great Basin bristlecone pine.
Age-related changes in foliar morphology and physiology in red spruce and their influence on declining photosynthetic rates and productivity with tree age
