Blogs / 80beats

Forest scientists have come to a surprising conclusion regarding old growth forests and their majestic, mature trees: They’re not just relaxing in their arboreal old age, but are still actively taking in carbon dioxide from the atmosphere. The new study suggests that protecting old growth forests may be just as important as planting new trees in efforts to reduce carbon dioxide levels and fight global warming.

Previously, researchers believed that only young, fast-growing trees absorbed enough carbon dioxide to be considered significant “carbon sinks.” Old, crowded forests don’t allow for much new growth: The only new growth occurred in the small spaces that opened up when large old trees died and decomposed, releasing their accumulated carbon. The forests at large were therefore considered to be carbon neutral, and accounted as such in climate models [Nature News]. But the new study shows that the slow but continuous growth of old trees means that they continue to suck up more carbon than they release.

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After running a batch of 300-year-old Stradivarius violins through a sophisticated medical scanner, researchers say they may have figured out why the aged instruments are revered for their tone, clarity, and power: The wood used for the ancient violins shows a more consistent density than that found in modern violins, and researchers argue that this difference may affect how vibrations travel through the wood.

In particular, the old wood shows less variation in density within growth rings, researchers say. Tree rings are comprised of a lighter, spongier portion that is produced during rapid spring growth and a darker, denser portion produced later in the year; in the Stradivarius wood these differences are less pronounced. Other researchers who have studied the activity of the Sun have pointed to a mini-Ice Age that occurred in the early 1700s. Experts say that this reduced solar activity, called the Maunder Minimum, could have hampered the regular growth of trees [BBC News].

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One hundred years ago today, a fireball streaked across the morning sky over Siberia and exploded, flattening the forest across an area of 830 square miles. The cause of the Tunguska Event, named for the nearby Tunguska River, has been a source of speculation ever since, with theories ranging from the absurd (space aliens!) to the most plausible: a disintegrating meteor exploding in the atmosphere. But a century after the event scientists still don’t have enough evidence to conclusively say what happened.

Scientists arrived at the most likely scenario, the meteor explosion, by studying the pattern of blasted trees; they concluded that an explosion hadn’t occurred at ground level, but rather four to six miles above the Earth’s surface. [T]he fragment, which is believed to have measured perhaps 100 feet across (although new research suggests it may have been even smaller), was probably traveling at around 21,000 miles per hour when it exploded…. Based on later assessments of the damage, the force of the blast was estimated to be between 10 and 15 megatons of TNT, roughly a thousand times more powerful than the atomic bomb that destroyed Hiroshima [Wired News].

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Who knew that a white spruce in northern Canada, a red maple in Pennsylvania, and a mahogany tree in Puerto Rico have so much in common? Their environments are certainly very different, with icy winds buffeting the spruce tree’s needles and hot, humid air bathing the mahogany tree’s leaves. But despite these external variations, a new study shows that inside each tree leaf (or needle) it’s always just the right temperature for the delicate and vital process of photosynthesis, and the leaves are responsible for keeping that thermostat steady.

The findings, published in Nature [subscription required], show that trees all across North America favor the temperature of 70 degrees Fahrenheit for the photosynthesis process, which uses sunlight to convert carbon dioxide into oxygen and sugars. To keep in that comfort zone, they’ve come up with some clever adaptations. Trees release water, and during hot times, that botanical sweat cools them down. And trees that grow in cold places tend to cluster their leaves. These tight formations can affect the rate at which leaves lose heat on cold days, just as fingers pressed together in mittens stay warmer than fingers separated by space in gloves [Science News].

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