Spring May Spring Earlier in Northern Forests

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The yearly south-to-north wave of spring green may begin weeks earlier due to continually warming temperatures with some trees springing into action earlier than others.

Late-budding trees, such as the red maple, will likely be the most affected over the next hundred years. Red maples may begin leafing out 8 to 40 days earlier than in the 20th century. Trees in northern states, such as Maine, New York, Michigan, and Wisconsin, will experience the greatest quickening of spring.

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Deciduous trees may receive a benefit from the changing climate, suggested biologists from Princeton University who published their study in the journal Geophysical Research Letters. With a longer growing season, broadleaved trees may be able to out-compete pine trees. Over time, this could lead to dramatic changes in the species mix of northern forests.

An earlier spring also means that trees will begin their yearly inhale of carbon dioxide earlier, which could increase the total amount of the gas that they absorb in a year.

The changing seasons cause observable global fluctuations of carbon dioxide levels. Atmospheric concentration of the gas decreases in summer when northern trees are pulling in carbon dioxide. The concentration goes back up in winter when northern trees become dormant. The seasonal zig-zag pattern can be seen in the overall rapidly increasing levels of carbon dioxide in the air.

Charles Keeling documented this seasonal fluctuation during more than four decades of observations at the Mauna Loa Observatory in Hawaii. His observations led to some the earliest direct observations that human activities are rapidly increasing the global concentration of carbon dioxide.

IMAGE: Boreal forest in Norway (Orcaborealis, Wikimedia Commons)

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