Old and ancient trees are life history lottery winners and vital evolutionary resources for long-term adaptive capacity

Trees can live for many centuries with sustained fecundity and death is largely stochastic. We use a neutral stochastic model to examine tree demographic patterns that emerge over time, across a range of population sizes and empirically observed mortality rates. A small proportion of trees (similar to 1% at 1.5% mortality) are life-history 'lottery winners', achieving ages >10-20x the median age. Maximum age increases with bigger populations and lower mortality rates. One-quarter of trees (similar to 24%) achieve ages that are three to four times greater than the median age. Three age classes (mature, old and ancient) contribute unique evolutionary diversity across complex environmental cycles. Ancient trees are an emergent property of forests that requires many centuries to generate. They radically change variance in generation time and population fitness, bridging centennial environmental cycles. These life-history 'lottery' winners are vital to long-term forest adaptive capacity and provide invaluable data about environmental history and individual longevity. Old and ancient trees cannot be replaced through restoration or regeneration for many centuries. They must be protected to preserve their invaluable diversity.

Automated summary

Trees can live for many centuries, and the longevity is largely random. A small proportion of trees can achieve ages much higher than the median age. The maximum age of trees increases with larger populations and lower mortality rates. Ancient trees are important for forest adaptive capacity and provide valuable information about environmental history and individual longevity. They cannot be replaced through restoration or regeneration and must be protected.