Fall is here: Why do some trees lose their leaves while others stay green?

The autumn has arrived and northeastern North America's forests will soon grace us with a breathtaking palette of reds, yellows and golds. These vivid colors will then fade, giving way to bare branches, as the fallen leaves blanket the forest floor, thereby returning their nutrients to the soil. The spectacle is not as impressive a few degrees farther north, where deciduous trees give way to conifers, which keep their dark green needles through the winter.