Microbes, soil and CO2: diversity is better

U.S. researchers: more microbes diversity helps soil to capture more carbon dioxide. Good news for climate, but soil health remains the key factor

by Matteo Cavallito

A hydrated soil with a wide variety of microbes is likely to sequester more carbon according to a team of scientists led by researchers Luiz A. Domeignoz-Horta and Kristen DeAngelis of the University of Massachusetts Amherst. The discovery has significant implications since carbon storage capacity is a key factor in climate regulation. The role of microbes in managing the cycles of key soil elements and preserving soil health is well-known. But the experiment conducted in the study is unique, the authors say. And it provides the first empirical evidence to support the claim.

Three key factors

At the heart of the survey lies an index known as carbon use efficiency (CUE) which is the balance between carbon assimilated by microbes and the amount released into the atmosphere. A higher spread means less impact on climate change. In order to measure the diversity effect, the researchers reproduced the ecosystem conditions in laboratory by changing some crucial properties in each case. The results were different soil performances.

Microbes at the core of the experiment

The team of researchers, which also includes Serita Frey of the University of New Hampshire and Jerry Melillo of the Ecosystems Center in Woods Hole, Massachusetts, extracted and then injected microbes at variable concentrations into selected soil portions. The scientists let five different microbial mixtures grow for four months and tracked oxygen levels under different conditions of species diversity, moisture and temperature.

“One interesting thing we found is that we do see that more diverse communities are more efficient” in capturing CO2, said Kristen DeAngelis. “Diversity is interesting, not just in microbiology but in all organisms, including humans.” Even in soil.

Soil health is crucial

Diversification, however, is just one side of the story. The positive effect of diversity on carbon use efficiency is neutralized in dry conditions and “this suggests that there’s a limit to the stress resilience with high diversity” scientists say. The experiment, in fact, shows that when drought is severe, the efficiency of microbes is diminished and the soil’s capacity to store carbon is compromised. It is not surprising, then, that to understand changes in soil carbon cycling we need to account for the multiple facets of global changes.” Protecting soil health in order to address the challenge of climate change, in other words, remains the most important factor.