An analysis of tracheid length versus age in a 4842-year old bristlecone pine (Pinus longaeva D.K. Bailey) called Prometheus.

摘要

After Prometheus, an ancient bristlecone pine (Pinus longaeva D.K. Bailey) located in the Great Basin National Park, had been cut down, it was determined that the tree had been the oldest living organism at over 5000 years of age. Great Basin bristlecone pines are famous for their longevity, living thousands of years under extreme conditions of temperature and moisture at high altitudes. For the majority of conifer trees, a period of rapid growth in tracheid lengths has been observed from the pith up to ten to forty years of age. Since most pine trees live for an average of 100-300 years, it was hypothesized that, for a tree with the potential to live thousands of years, the juvenile growth phase might be of longer duration than trees that live much shorter lives. Tracheid lengths were measured from century sample points on Prometheus, as well as points near the pith and the year of felling. A juvenile growth phase was identified that lasted at least one hundred years. In addition, an unusually strong decrease in tracheid length at the year -800 was noted and commented upon. Crossdating was successful between Prometheus and two local bristlecone tree ring chronologies. Additional observations revealed the presence of many partial rings which reinforces the importance of crossdating Prometheus to bristlecone tree ring chronologies in order to determine its true age. The mean tracheid length data were compared to Salzer and Kipfmueller (1998) reconstructed temperature and moisture episodes. Tracheid lengths decreased during warm periods and increased during cool periods. These results confirmed that warm periods increase the length of the growing season, resulting in the production of shorter tracheids. When the mean widths of one-hundred-year intervals of Prometheus were compared to long-term climatic events, the ring widths were wider during the cooler period, narrower during the warmer period, and the widths spiked during two of the Bond events. This is contrary to the belief that warm periods result in wider rings, therefore it was determined that water stress during the warm period and abundant water availability during the cool period were the likely causes of the variable ring widths.