Global warming also affects forests and subarctic peatlands

Researchers from the Center for Nordic Studies (CEN, Universite Laval, Quebec) have just documented two manifestations of global warming in northern Quebec. The first affects the acceleration of permafrost melting in subarctic peatlands, and the second the increase in the rate of vertical growth of trees at the forest line.
In a recent issue of Geophysical Research Letters, researchers are using data accumulated on a peat bog located at the 56th parallel, east of Hudson Bay, to describe the evolution of permafrost in this habitat.
The researchers used an aerial photo taken in 1957 and data collected from the field during visits made every ten years between 1973 and 2003. They found that the percentage of the peatland area occupied by permafrost increased from 82 % in 1957 to 13% in 2003. Its rate of disappearance has doubled since 1993. According to researchers, the main cause of this acceleration is the increase in precipitation in the form of snow; the snow cover protecting the ground against the frost wave and buffering the temperature differences. The impact of the degradation of peatlands on the balance of greenhouse gases remains to be measured.
In addition, global warming models predict that the current northern limit of forests will gradually be pushed north. In a recent article published in the Journal of Ecology, researchers predict that the northern expansion of black spruce - a species with limited reproductive capacity - should be preceded by a change in the habit of these trees: according to their analyzes the stem main tree has experienced accelerated vertical growth since the early
1970s. If current conditions continue, spruce trees will continue to grow vertically and produce more cones and seeds; this should favor the northern expansion of the tree line.

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Sources: Jean Hamann - Through the events, 10/03/2005 - Universite Laval

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