Warming tundra breaks

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With decomposition, due to the increase in temperature, the Tundra will produce carbon dioxide and thus further accelerate the warming.
Until now, most studies predicted that global warming would tundra greener area. Under this scenario, the plants that occupy it would develop rapidly by storing more of carbon dioxide. Paul Grogan, specialist of northern ecosystems to Queen's University, and colleagues lead to the opposite conclusion: they believe that the warming will also promote the decomposition of peat, moss and other plants. And this will increase about 25% concentration of carbon dioxide in the atmosphere. Michelle Mack, who led the study, studied plots artificially fertilized in Alaska. Adding to their soil nitrogen and phosphorus, it has reproduced the nutritional quality that would produce a pronounced warming of the arctic area. 1981 between early experience and 2000, soils studied it incurred a net loss of 2 kilograms of carbon per square meter. The largest loss occurred over 5 cm below the soil surface. She had gone unnoticed until now because the measures covered only the surface layer.
As the ground warms, microbial activity increases. Micro-organisms digest organic matter and release of carbon dioxide as well as nitrogen and phosphorus, which stimulates the growth of plants. This growth has doubled with global warming: shrubs fifty centimeters now replacing sedge [compact grass] pushing along the ground. But the amount of carbon emitted by accelerating the decomposition exceeds that absorbed by this new cover.
Paul Grogan and Michelle Mack emphasized that their experiments have focused on one aspect of the carbon cycle, which takes place in complex ways between the atmosphere and the earth: the effect of increased nutrients in the soil. These results do not necessarily apply to other northern areas like the immense boreal peatlands or polar desert. And to consider other environmental factors such as melting permafrost and warming of the soil, the researchers said. However, "these results challenge some of our assumptions. Was once thought that if we had more plants and trees, it automatically was storing carbon, if only temporarily, "said Tim Moore, a geography professor at McGill University, who studies the carbon cycle in a bog near Ottawa.
Peter Calamai The Toronto Star

Source: Courier Internationnal


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