Old-growth forests store far more carbon than managed forests.

A study reports that undisturbed primary forests in Sweden contain about 83% more carbon per acre than nearby managed forests when harvested wood products are excluded, and that most of the difference is in soils.

Researchers led by teams at Lund University and Stanford University published a study in Science reporting that undisturbed primary forests in Sweden hold substantially more carbon per acre than the managed forests replacing them. The team mapped old-growth forest areas and measured carbon at more than 200 plots over three years. They combined those field measurements with decades of national forest and soil carbon inventory data and statistical models to estimate carbon across vegetation, dead wood, soil, and harvested timber. Key findings: - The study reports undisturbed primary forests store about 83% more carbon per acre than managed forests when harvested wood products are excluded, and about 72% more when those products are counted. - Most of the carbon difference is reported to be in soils beneath the forest floor. - The analysis used measurements from more than 200 plots plus decades of national inventory data and statistical models to quantify carbon across forest pools. - The reported gap is 2.7 to 8 times larger than current official estimates, and the authors say restoring managed-forest carbon to primary-forest levels in Sweden would correspond to nearly 8 billion tons of CO2 not entering the atmosphere. Summary: The study indicates that replacing primary forests with managed, often single-species stands is associated with substantially lower carbon storage per acre, largely due to losses in soil carbon. Undetermined at this time.