Beetles are eating the boreal forests of Canada and Russia. Drought-tolerant pines are disappearing in Greece. Wet and dry tropical forests in Asia are collapsing. Australian eucalyptus forests are burning. The Amazon basin has been hit by two severe droughts. Scientists think American Southwest trees may disappear by 2100. But exactly how do trees die from thirst or starvation, and why do some survive? Nate McDowell at Los Alamos labs is trying to find out, reports Sandra Blakeslee at the New York Times. Unlike previous megadroughts, which ultimately ended, global warming droughts are developing faster and expected to continue with warming. Even if precipitation remains unchanged, warmer air will wick moisture away from trees. Doing so, causes the tiny ropes of water that are sucked up through trees to break, allowing air into these pathways. Many trees worldwide are close to such hydraulic failure. Others fight water loss by closing leaf pores, the escape exits. But this shuts off photosynthesis, vital to trees. After depleting stored food, trees then face death through thirst or starvation. Understanding exactly how this happens will help predict future losses.
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As forests disappear, examining the mechanisms of their death. Everywhere, trees are dying. The boreal forests of Canada and Russia are being devoured by beetles. The Amazon basin has just been hit by two severe droughts. And it’s predicted that trees in the American Southwest may be gone by the end of this century. New York Times http://www.nytimes.com/2012/12/25/science/los-alamos-national-laboratory-studies-tree-deaths.html?_r=1&
*****The Amazon Rainforest is drying as two catastrophic droughts and increased deforestation increase losses, making it more difficult for remaining trees to adapt, says a researcher who is monitoring it, reports Barbara Fraser at Scientific American. http://www.scientificamerican.com/article.cfm?id=amazon-rainforest-drying-out