Soil texture key in deforestation

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Photo by Alexandra Schmeling.

A new Yale study reveals soil texture is key to understanding the vulnerability of an ecosystem to deforestation.

Researchers led by postdoctoral fellow Thomas Crowther from the Yale School of Forestry and Environmental Studies have identified soil texture as a defining characteristic for predicting the effects of deforestation. While current understandings of deforestation are drawn from a small number of studies whose results are location-specific, Crowther’s study considers 11 different sites ranging from Alaska to Hawaii. The finding, which was published in Global Change Biology on April 1, allows researchers to predict where deforestation will have the most substantial effect. It will also be important in determining forest management practices that aim to lessen the impact of climate change.

“We expected [deforestation would depend on] a sweep of characteristics like temperature, moisture and nutrients in the soil,” Crowther said. “But we found that really it’s the texture of the soil — which varies on a scale of very sandy coarse particles to very tiny fine muddy particles — determines almost entirely the effects of deforestation.”

Over three years, Crowther and his research team collected soil samples from all 11 sites annually. Each sample was divided up and studied for different attributes including the amount of carbon and nitrogen present, soil texture, effect of different temperatures and microbial analysis.

Changes to the soil impact climate change both through soil release of carbon and decreased tree density. Crowther said the study demonstrates the importance of considering the underground microbial community when addressing effects of deforestation because of soil’s important role as a carbon sink. If forests are cut down at sandy sites, all water and nutrients are lost and the microbial community changes very rapidly in response, Crowther explained. That response causes a significant increase in the amount of carbon lost from the soil.

Wherever the soil is likely to hold onto nutrients and retain water and reduce the effects of disturbance, the land is less vulnerable to effects of deforestation, Crowther said.

Kevin Dennehy, the communications officer at the F&ES, pointed to the importance of addressing the underground carbon sink instead of thinking of trees as the only lost carbon sink. Dennehy added that this study is “special and meaningful” because it aligns with the goals of F&ES by tackling deforestation on a global scale.

“Other studies have found that forest removal can have effects on soil microbes at very specific sites, but in this case, because the researchers took into account so many different climate types from Northern Alaska to Hawaii, their findings have the potential to be applicable to ecosystems globally and to inform forest management strategies in all parts of the world,” Dennehy said.

Hefin Jones, a soil ecologist from Cardiff University not involved in the study, said in an email that this study is a valuable advance for the understanding of soil biodiversity. He added that soil microbes are essential components of natural ecosystems, and that it is important to identify the location of the communities most vulnerable to land use change.

Even though the study was based on data from 11 locations, Crowther said the topic needs to be studied at more sites to verify the effect. A more detailed understanding of which parts of the soil community are likely to change could help researchers predict the nature of change, he said.

According to Greenpeace UK, carbon released from deforestation contributes up to one-fifth of global man-made emissions — more than the world’s entire transportation sector.

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