As plants die, fall to the ground and decay, the amount of carbon stored in the soil and ground moss rises over centuries to millennia. In the Russian boreal forest, most fires are ignited by lightning strikes hitting trees or the ground. In relatively dry summer seasons, like 1998, thousands of fires are started by lightning, consuming millions of acres of boreal forest lands. Most of these fires not only consume trees, but also burn the top layers of soil, thereby releasing the carbon stored there too. Of concern to Earth scientists is the impact widespread boreal fires have on climate.
Fires release huge amounts of smoke, carbon dioxide, and methane into the atmosphere.
Some scientists are concerned that extreme fire seasons in the boreal forest, like last year's, may contribute to global warming. Others point out that when a region is disturbed by fire, there is vigorous regrowth that could offset global warming. The rationale is that while the younger plants are growing back they are absorbing carbon dioxide back out of the atmosphere and using the carbon to build plant structures. In the immediate aftermath of a fire the burned area appears lifeless and desolate, but new growth will soon replace stands of charred, dead trees. In some areas of the Canadian boreal forest, jack pine is the first species to appear.