Soil Doesn’t Forget

Ecologists need to understand what and where soil microbes live in Earth’s ecosystems—these microorganisms can influence what can thrive above. But there’s a gap in the field: Today’s climate conditions do not fully explain the types of microbes they see. So CIRES researchers at the University of Colorado Boulder are looking thousands of years back in time—and they’re finding answers.

“We found that paleoclimate explained a unique proportion of the variation in soil bacterial communities that could not be explained by other factors,” said Manuel Delgado-Baquerizo, a researcher in CIRES Fellow Noah Fierer’s group. “If we look at two similar grasslands, for example, we may find they have completely different microbial communities. Our work finds that some of those differences are due to the climate thousands or tens of thousands of years ago.”

The study, which included data from more than 1,000 terrestrial ecosystems from around the world, was published today in Nature Ecology and Evolution. It highlights findings that show past climate can be a better predictor of soil microbes than factors such as soil properties, current climate, or location. These paleoclimates most likely affect modern soils through long-lasting effects on the trajectories of microbial community development in soil.

Soil microbes are vital to nearly every function of an ecosystem: photosynthesis, nitrogen and phosphorus mineralization, plant development, even climate regulation. By studying the response of soil microbial communities to present and ancient climates, scientists can better understand how soil communities may change in response to climate change in the future.

Agriculture makes this challenging, the scientists found. When farmers develop croplands, they disturb the upper layer of soil, completely resetting the ecological system—and globally, this type of soil disturbance is rapidly increasing. “It’s like the ecosystem is a book,” said Delgado-Baquerizo, “When the cropland is created, they are erasing the words from a story that took millennia to write.”