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Viewings: 4103Majestic age-old forest may seem immortal, but in reality they are on the verge - because of global warming.
Transfer of water from the root to the tip going to xylem is tiny, but numerous canals. The pores in the leaves let the water evaporate, and it evaporation draws water up the tree with more force than dry soil - down. But when a certain threshold dryness "effort" of the tree, seeking to draw more water from the land, leads to the fact that in the xylem are bubbles of air from the surrounding tissue. They score the canals, and the flow of water stops at all.
Global warming brings not only drought, and pests disease. (Photo By Patrick Marella.)
Steven Jansen from the University of Ulm (Germany) and his colleagues decided to find out what types of trees are more at risk to collide with hydraulic failure, that is especially vulnerable to drought. The researchers collected data on 226 trees from 81 locations and calculate margin of safety on the basis of the difference between the pressure in the xylem for drought and when hardening half of xylem.
Scientists had thought the trees of the dry places reserve of strength more, because they would seem already to adapt to the dry weather. But in fact 70% of the trees has a small safety margin regardless of environmental conditions. The most vulnerable are flowering plants - unlike gymnosperms. In General, it turns out, wherever a drought come on, trees there bad, whatever the conditions.
Craig Allen from the U.S. Geological survey, who did not participate in the study, explains that the trees have evolved in accordance with its environment, adapting to what they had to face in real life. And global climate change is expected to more extreme conditions. To predict the change in precipitation pattern is difficult, but that the temperature will rise, no doubt.
By the way, do not forget about the feedback, that is about photosynthesis, which air is removed carbon dioxide. Dead wood will do the opposite.
The study is published in the journal Nature.
Based on the materials ScienceNOW.
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