Diversity of soil microbial communities helps regulate climate change

Scientists have reported that changes in the diversity of soil microbial communities can alter the ability of the soil to sequester carbon, where it often helps to control climate.

Test tube fungus (left) and test tube soils (right). Image Credit: University of Massachusetts Amherst/Luiz A. Domeignoz-Horta.

According to the researchers, headed by postdoctoral researcher Luiz A. Domeignoz-Horta and the study’s senior author Kristen DeAngelis from the University of Massachusetts Amherst, this is the first-of-its-kind study to be performed, to date.

The researchers also observed that the positive influence of diversity on carbon use efficiency—which plays a major role in that storage—is effectively neutralized in dry conditions.

The term carbon use efficiency denotes carbon that is assimilated into microbial products against the carbon that is lost in the air in the form of CO₂ and contributes to climate warming, explained DeAngelis. Among other advantages, soil carbon ensures soil health by retaining water and helping plants to grow.

DeAngelis and her collaborators tackled these questions because they noted that “empirical evidence for the response of soil carbon cycling to the combined effects of warming, drought and diversity loss is scarce.”

To investigate further, the researchers experimentally exploited microbial communities while modifying factors, like the composition of microbe community species, soil moisture, and temperature. The study results were published in the Nature Communications journal.

Besides the study’s first author Domeignoz-Horta and others from the University of Massachusetts Amherst, the research team includes Serita Frey from the University of New Hampshire and also Jerry Melillo from the Ecosystems Center, Woods Hole, Massachusetts.

The researchers pointed out that soil carbon is partly controlled by the efficiency and rate with which the microorganisms thriving there can utilize fresh plant foods and other portions of soil organic matter to grow.

Soil carbon pools can stick around for decades and turn over very slowly. These are ones we really want to have because they help soil stay spongy to absorb water and help bind and release nutrients for plant growth.”

Kristen DeAngelis, Study Senior Author, Department of Microbiology, University of Massachusetts Amherst

She continued, “Diversity is interesting, not just in microbiology but in all organisms, including human. It’s controlled by a lot of different factors, and it seems that more diverse systems tend to work more efficiently and to tolerate stress better. We wanted to understand the role of microbial diversity in soil carbon efficiency.”

“Replicating diversity is tricky, which is why we used a model system soil. Luiz extracted microbes from soil, made serial dilutions of microbe concentrations in a buffer and inoculated the soil to get variation in diversity,” DeAngelis further added.

They allow the five different combinations of microbes to grow for a period of 120 days. Besides other tests, the team employed a novel technique built on a heavy and stable isotope of water called 18O-H₂O. It enabled the researchers to detect the oxygen and monitor new growth over time in the varying diversity, temperature conditions, and soil moisture.

One interesting thing we found is that we do see that more diverse communities are more efficient. The microbes grow more than in less diverse communities, but that increase in growth with diversity is lost when they are stressed for water. This suggests that there’s a limit to the stress resilience with high diversity.”

Kristen DeAngelis, Study Senior Author, Department of Microbiology, University of Massachusetts Amherst

The study’s authors further emphasized, “Results indicate that the diversity by ecosystem-function relationship can be impaired under non-favorable conditions in soils, and that to understand changes in soil carbon cycling we need to account for the multiple facets of global changes.”

We were a little surprised at how our approach worked so well. I’m really interested in the temperature/moisture efficiencies and Luiz is more interested in the diversity angle. It was a combination of the two that was the most interesting result.”

Kristen DeAngelis, Study Senior Author, Department of Microbiology, University of Massachusetts Amherst