Increased droughts are disrupting carbon-capturing soil microbes, concerning ecologists

Soil stores more carbon than plants and the atmosphere combined, and soil microbes are largely responsible for putting it there. However, the increasing frequency and severity of drought, such as those that have been impacting California, could disrupt this delicate ecosystem.

In a U.S. National Science Foundation-supported perspective in the journal Trends in Microbiology, microbial ecologist Steven Allison warns that soil health and future greenhouse gas levels could be impacted if soil microbes adapt to drought faster than plants do. He argues that we need to better understand how microbes respond to drought so that we can manage the situation in both agricultural and natural settings.

"Soil microbes are beneficial, and we couldn't live without their cycling of carbon and nutrients, but climate change and drought can tweak that balance, and we have to be aware of how it's changing," says Allison of the University of California, Irvine.

Some soil microbes take carbon from decomposing plants and store it in the soil, while others release plant carbon back into the atmosphere. The carbon that ends up in the soil is beneficial in multiple ways.

"The carbon in the soil has these reverberating effects out to the rest of the world in terms of the infrastructure in our natural and managed ecosystems," says Allison. "Carbon-rich soils hold more nutrients, so plants growing in those soils tend to be more productive, and the carbon changes the physical properties of the soil, which prevents erosion.

"In California now, we have this system where the droughts are more intense, and then the rainfall is more intense," he says. "If you're losing your soil carbon, when it rains really hard it could carry away your soil and cause erosion, landslides, mudslides, sediments and all kinds of problems that we're actually seeing right now."

Adds Matt Kane, a program director in NSF's Division of Environmental Biology, "The microbes found in soil are extremely diverse, and understanding how their populations shift in response to environmental change is essential to predicting future land use change."