Seven millennia of population dynamics in a high-altitude population of bristlecone pine

Very few study systems offer the ability to examine the detailed population and community-level dynamics of long-lived species on time-scales relevant to their life history, or to probe the climatic controls on population behavior over more than a few decades. The Bristlecone pines (Pinus longaeva) of the White Mountain Range are not only the longest-living (non-clonal) species on record, but deceased individuals and relict wood can remain intact for millennia in their cold and dry high elevation environment. To better understand the forces promoting longevity and limited recruitment of long-lived trees, I used dendrochronological analyses to reconstruct the spatial and temporal history of a high-altitude Bristlecone population with a relict wood record spanning 7000 years. I found substantial variability in population growth rate, age distribution, and demographic rates of trees over this period of time. Of currently alive individuals, the majority recruited during either the medieval warm period (800-1300 AD), or after 1850 AD, with little establishment during outside these periods. I also find substantial variation in mortality rates, some of which is correlated with climatic conditions. The center of the population has also shifted considerably over the last six millennia as population numbers have increased, and average nearest neighbor distances have dropped to about 20 meters from a high of 120 meters. Trends in recent recruitment and investigation of old photographs shows remarkably low juvenile mortality and an enormous increase in 20th century recruitment into juvenile classes for both Bristlecone and Limber pine (Pinus flexilis). Understanding the population-level consequences of extreme longevity and the actual response of population vital rates to stochastic events and climate changes can provide an important test of the applicability of normal demographic methods to long-lived species.