Bristlecone pines have an extremely slow rate of growth. The summer months are very short-lived; new cones and twigs must be formed at this time and reserves stored for the long over-wintering phase. If trees are damaged by fire or drought, their living tissues will die back retaining only what can be sustained by the tree, thus much of the tree appears dead but it is still able to produce cones with viable seeds in the summer months (5).
Tree growth rings reveal the age of an individual tree but can also provide insights into past climates. Pines produce wide growth rings in generally good conditions, that is, sufficient moisture and good soil, and narrow growth rings form in poor conditions: little moisture and poor soil. By studying these growth rings, light can be shed on past climatic events (5). Because bristlecone pines are such old organisms, and because their timber persists for an incredibly long period after death (3), the study of the wood of these ancient trees has revealed environmental conditions stretching back to almost 9,000 years ago (4) (5).