Deforestation in Sandy Soil Ecosystems Releases Most CO2 into Atmosphere

The disruption of underground microbial communities caused by deforestation and the effects of climate change on forest ecosystems will be greater in some soil types, such as sandy soils, than in others, according to a new study led by Yale University researchers.

The revelation may provide critical ecosystem-management information for areas prone to biodiversity loss, as well as highlighting which ecosystems are more resilient to widespread tree removal.

Writing in the journal Global Change Biology, the researchers report their analysis of soil collected from 11 distinct US regions, finding that soil texture is extremely significant in determining carbon loss to the atmosphere when underground microbial communities are disturbed because of deforestation.

"We were astonished that biodiversity changes were so strongly affected by soil texture and that it was such an overriding factor," lead study author Thomas Crowther, a postdoctoral fellow at the Yale School of Forestry & Environmental Studies, said in a statement. "Texture overrode the effects of all the other variables that we thought might be important, including temperature, moisture, nutrient concentrations, and soil pH."

Crowther conducted the researcher with scientists from University of Boulder, Colorado and the University of Kentucky.

When a forest is lost due to logging or other forms of deforestation, a significant amount of carbon stored within the soil is unleashed. As the microbial community in a newly deforested area changes, even more carbon will be released, the researchers report, noting that this additional CO2 escaping into the atmosphere has the potential to exaggerate global warming.

Following deforestation, the soils most prone to releasing excess carbon are sandy soils, which retain less nutrients and have larger particles with less surface area. In muddy, clay-like soils, the particles have greater surface area to bind nutrients and water, allowing these soils to retain more nutrients and organic matter.

"If you disrupt the community in a sandy soil, all of the nutrients the microbes rely on for food are leached away: they're lost into the atmosphere, lost into rivers, lost through rain," Crowther said. "But in clay-like soil, you can cut down the forest and the nutrients remain trapped tightly in the muddy clay."

Surprisingly, the researchers found no correlation with how the effects of deforestation on microbial diversity change over time.

"The effects are consistent, no matter how long ago deforestation happened," Crowther said. "In a clay soil, you cut down the forest and the nutrients are retained for long periods of time and the community doesn't change. Whereas in a sandy soil, you cut down a forest and the community changes dramatically within only a couple of years."