REDUCTIONS IN TREE-RING WIDTHS OF WHITE-PINE FOLLOWING OZONE EXPOSUREAT ACADIA NATIONAL-PARK, MAINE, USA

Polluted air masses from the industrialized northeastern corridor of t he United States flow through Acadia National Park, Maine, U.S.A. The polluted air masses create elevated ozone episodes throughout the grow ing season, causing visible foliar damage to some native plant species . This study used dendroclimatic techniques to investigate the possibi lity that elevated ozone levels adversely affected white pine (Pinus s trobus L.) radial growth rates. Tree-ring cores were extracted from wh ite pine trees in eight separate stands within the park. Tree-ring ind ices were then regressed with ozone variables to model the effects of elevated ozone levels on tree growth under field conditions. Models fr om seven of the eight stands documented negative associations between tree-ring indices and ozone levels that were stronger than any associa tions between tree-ring indices and climate. The modeled growth-ozone associations exhibited stand-level variations, suggesting that site ch aracteristics affect tree responses to ozone pollution.