Global warming also affects forests and subarctic peatlands


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Researchers from the Nordic Studies Center (CEN, Universite Laval, Quebec) have just documented two global warming events in Northern Quebec. The first concerns the acceleration of permafrost melt in subarctic peatlands, and the second is the increase in the rate of vertical growth of trees at the edge of forests.
In a recent issue of Geophysical Research Letters, researchers use accumulated data from a peat bog at the height of the parallel 56e east of Hudson Bay to describe the evolution of permafrost in this habitat.
Researchers used an 1957 aerial photo and field-collected data from visits every 10 years between 1973 and 2003. They found that the percentage of peatland occupied by permafrost went from 82% 1957 to 13% 2003. Its disappearance rate has doubled since 1993. According to the researchers, the main cause of this acceleration is the increase in precipitation in the form of snow; the snow cover protecting the soil against the freezing wave and buffering the temperature differences. The impact of peatland degradation on the greenhouse gas balance remains to be measured.
In addition, global warming models predict that the current northern forest limit will be progressively pushed northward. In an article recently published in the Journal of Ecology, researchers predict that 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 The main tree has experienced accelerated vertical growth since
1970 years. 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.

Sources: Jean Hamann - On the go, 10 / 03 / 2005 - Laval University
http://www.scom.ulaval.ca/Au.fil.des.evenements/2005/03.10/tourbieres.html

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