To understand better the long-term impact of air pollutants on the health of pine trees in California, researchers have developed a new method to analyze cumulative biochemical changes in tree rings. Using cell structures in tree trunks, scientists from UC Davis and the U.S. Department of Agriculture's Forest Fire Laboratory have been able to compare the woody tree tissue deposited from 1900-1940 with that of 1950 to the present. The new method allows the scientists to observe long-term trends consistent with historical air pollution patterns, says Teresa Fan, a researcher in the UC Davis land, air and water resources department. "Until now, it's been difficult to identify the culprits, because no biological or biochemical indices exist to corroborate the cause-and-effect relationship," Fan said. For example, she says, it's been difficult for scientists to know whether pine tree damage is from ozone and/or drought conditions. Looking at wood is extremely complex and components cannot be reliably extracted for analysis, she says. This new method uses the wood as is, without any extraction. Fan will present the researchers' findings about the work at an ecosystem health conference to be held at UC Davis Tuesday, Sept. 10, and Wednesday, Sept. 11.