Temperature and precipitation seem to have the biggest impact on leaf color, said Neufeld, who publishes an annual fall color report. "Conditions leading up to the fall were ripe for good fall color -- sunny, cool, no severe drought," he told Boyd. "But they didn't develop. I don't know why that is." But he does provide a theory: trees produce volatile organic compounds, which reflect the sun's radiation back into space. This "VOC armor" will not stay strong forever, Boyd writes. "It will weaken as the climate warms, and will one day demonstrate the same higher temperatures as most of the rest of the country."
Plants are cooled by evaporating water through their leaves, but "many tree leaves were were damaged as a result of the inability of root systems to supply sufficient water to leaves that experienced high temperatures" this year, Cornell University plant biologist Karl Niklas told Boyd. "The damage to leaves earlier in the season meant that many leaves could not color up or simply died while still attached." (Read more)