Print PageAs trees simultaneously age and grow, they, like animals experience senescence and a seeming decrease in vigor, ultimately leading to death. However familiar the phenomenon, the mechanism responsible for plant ageing has proven difficult to assess. In trees, recent studies have pointed to a size-dependent reduction of growth. This size-dependent reduction of growth leads to both intra and interspecific fitness tradeoffs of growth rate and longevity in trees. This tradeoff between longevity and growth rate has recently been demonstrated in three North American tree species. In order to test for the presence of this tradeoff in a broader array of species, I utilized growth data from the International Tree Ring Database of 15 conifer species, from 120 sites scattered across the Northern Hemisphere. A Bayesian analysis was performed, tracking deviation from mean growth at each timestep for each individual. If indeed an age-longevity tradeoff exists in Northern conifers, then one would expect fast growing trees to reach a maximum size at a younger age than slow-growing trees.
Results/Conclusions
Analyses demonstrated that individuals from fast-growing age-size cohorts experience a more rapid decrease in growth than slow-growing individuals. This effect was demonstrated both inter- and intraspecifically. For example, in Pinus sylvestris slow growing individuals (<20th percentile) overtook fast growing individuals (>80th percentile) by an age of 300 years. These tradeoffs could be due to local abiotic and biotic conditions, with fast growing trees being located in more favorable habitats. The exact mechanisms of this growth-longevity tradeoff require further study, but quantifying growth-longevity tradeoffs in northern conifers helps inform our decisions of forest management in our changing climate. The quantification of growth-longevity tradeoffs in these 15 conifer species assist in making more informed predictions of how trees and forests may respond to climate change. Both intra and interspecific growth rate-longevity tradeoffs could be very important factors in estimating the effects of CO2 fertilization and a changing climate on forest communities.
