I commented to several friends last Fall that I thought autumn came late this year. It seemed that in my part of the country (south-central Pennsylvania) the peak Fall foliage display was about three weeks later than it was a decade ago. I wasn't sure why this should be since I had always thought that the onset of the pigment change was related to conditions like temperature and day length which surely weren't significantly different than they were ten years ago. Nor did I see anything written about autumn's tardiness anywhere, but I was pretty certain I wasn't imagining it. So, when I came upon this story at Science Daily it naturally piqued my interest:
Do those fall colors seem to show up later and later-if at all? Scientists say we can blame increasing amounts of carbon dioxide in the atmosphere for prolonging the growing season of the trees. And that may actually be good news for forestry industries.
Writing in the current issue of the journal Global Change Biology, Michigan Technological University Professor David F. Karnosky and colleagues from two continents present evidence that rising carbon dioxide levels in the atmosphere act directly to delay the usual autumn spectacle of changing colors and falling leaves in northern hardwood forests.
"Basically, this is a good-news story for our region's forests," said Karnosky. "It suggests that they will become a bit more productive due to the extra carbon being taken up in the autumn, along with the increased photosynthesis throughout the growing season."
They found that the forests on both continents stayed greener longer as CO2 levels rose, independent of temperature changes....There has been plenty of evidence gathered previously to show that increased carbon dioxide in the atmosphere is causing tree growth to begin earlier in the spring, but until now, most scientists believed that other factors, such as temperature and length of day, were the primary elements influencing autumnal senescence.
This raises some fascinating questions. How sensitive are these plants to CO2 changes? How much of a change in CO2 concentration is necessary to trigger such a profound difference in the timing of senescence? If CO2 increases just a little bit more will deciduous trees hold their leaves all year round? What are the ecological and economic implications of all this?
If anyone knows the answers to any of these questions, let me know.
RLC