ESTIMATING WATER INPUT BY METASEQUOIA INTO HIGH-LATITUDE EOCENE PALEOENVIRONMENTS

Rainforest ecosystems are thought to have existed in arctic environments during the Eocene (57.8- 36.6 Ma) with humidity estimated at 67% and mean annual temperatures ranging from 8.2 to 17.2 ^oC. Based on previous studies, paleo-vapor pressure may have been as high as 8.2 mm Hg indicating atmospheric water content twice that which exists above modern day Tundra ecosystems. Fossil evidence indicates high-latitude environments of the Eocene were widely forested with large tree species that may have pumped vast quantities of water into the atmosphere much like the rainforest trees of Amazonas in present day. One such member of the Eocene rainforest is Metasequoia, a genus in the Taxodiacea family that is known for the largest and longest-lived trees. Although the distribution of modern day Metasequoia is restricted to isolated pockets, the xylem anatomy of this genus permits rapid height growth and crown development indicating that in the past Mestasequoia may have grown similarly to modern day Sequoia sempervirens, producing stands of tall trees dominating the landscape. Here, we synthesize tree ring measurements and xylem anatomy from exquisitely preserved Metasequoia wood from the mid Eocene with a model of hydraulic conductance to estimate water input by this species. Results are presented for individual trees of varying age classes and ecosystems characterized by high and low densities of Metasequoia stands.