Soils, the Largest Land-based Carbon Storage System, Cushion Earth from Warming

Research by microbial ecologist Kristen DeAngelis at the University of Massachusetts Amherst advances understanding of the role of soil microbes in feeding carbon into the atmosphere and contributing to global warming.

Soils are the largest repository of organic carbon in the terrestrial biosphere and represent an important source of carbon dioxide (CO2) to the atmosphere, DeAngelis says. Her investigations could unlock promising new ideas for curbing the effects of climate change. One of the implications of her studies could be remediating soil to improve its ability to store carbon.

Soils perform an important ecosystem service by storing carbon, preventing its release as greenhouse gases into the atmosphere. DeAngelis conducts many of her studies on research plots at Harvard Forest, a research station in Petersham, Mass., to address how climate change affects soil carbon, and how carbon-use efficiency (CUE) may work as a possible source of climate-altered feedbacks to warming. CUE refers to the difference between carbon assimilated into microbial products versus carbon lost to the atmosphere as CO2, and contributing to climate warming. Among other benefits, soil carbon makes soil healthy by holding water and helping plants grow.

Most recently, in a first-of-its-kind study, DeAngelis and colleagues report that shifts in the diversity of soil microbial communities can change the soil’s ability to sequester carbon, where it usually helps to regulate climate.They also found that the positive effect of diversity on CUE – which plays a central role in that storage – is neutralized in dry conditions.

One goal of DeAngelis’s work is to contribute new information to models that estimate how much the planet will warm but which at present do not account in an explicit way for the microbial contributions, a major contribution to global carbon cycling. 

“We want to improve these techniques by helping them to incorporate microbes in carbon cycle models,” DeAngelis says.

Another recent key finding by DeAngelis and colleagues is that more diverse microbial 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. The diversity-by-ecosystem-function relationship can be impaired under non-favorable conditions in soils. To understand changes in soil carbon cycling, scientists need to account for the multiple facets of global changes.