PORTLAND, Maine (AP) — As trees show autumn's gold, orange and red hues, nature lovers aren't the only ones taking note of the dazzling display: Scientists are watching trees and recording the time that leaves change as they seek to determine the impact of climate change.Researchers have recorded earlier budding of plants in the spring. Now they're turning their attention to documenting fall foliage in the U.S.Richard Primack, professor of biology at Boston University, says studies in Europe and in Japan already indicate trees are changing color and dropping leaves later because of warmer temperatures. He says it stands to reason that's happening in the U.S., but there's no definitive study.Scientists say there could be implications for ecology and the economy — dull or delayed colors could discourage leaf-peeping tourists.