Surface appearances can be so misleading: in most forests, the amount of carbon held in soils is substantially greater than the amount contained in the trees themselves.
If you're a land manager trying to assess the potential of forests to offset carbon emissions and climate change by soaking up atmospheric carbon and storing it, what's going on beneath the surface is critical.
But while scientists can precisely measure and predict the amount of above-ground carbon accumulating in a forest, the details of soil-carbon accounting have been a bit fuzzy.
Two U-M researchers and their colleagues helped to plug that knowledge gap by analyzing changes in soil carbon that occurred when trees became established on different types of non-forested soils across the United States.
In a paper published online April 1, 2013 in the Soil Science Society of America Journal, they looked at lands previously used for surface mining and other industrial processes, former agricultural lands and native grasslands where forests have encroached.
U-M ecologist Luke Nave and his colleagues found that, in general, growing trees on formerly nonforested land increases soil carbon. Previous studies have been equivocal about the effects of so-called afforestation on soil carbon levels.
"Collectively, these results demonstrate that planting trees or allowing them to establish naturally on nonforested lands has a significant, positive effect on the amount of carbon held in soils," said Nave, an assistant research scientist at the U-M Biological Station and in the Department of Ecology and Evolutionary Biology.
"These forest soils represent a significant carbon reservoir that is helping to offset carbon emissions that lead to climate change," said Nave, lead author of the paper.
Co-authors of the Soil Science Society of America Journal article are Chris Swanston of the U.S. Forest Service, Umakant Mishra of the Argonne National Laboratory and Knute Nadelhoffer, director of the U-M Biological Station and a professor in the Department of Ecology and Evolutionary Biology.
U-M News Service press release