Microbes in soil respond differently to plants that are rich in carbon than to those rich in nitrogen, according to new research by postdoctoral fellow Rose Abramoff of Berkeley Lab’s Earth and Environmental Sciences Area and colleagues at the University of Maryland and Boston University. Abramoff is an ecologist working in the Climate Sciences Department within EESA’s Climate and Ecosystem Sciences Division.
The researchers developed a new mathematical model for predicting how soils react to various temperatures and to different types and amounts of moisture and plant inputs. After testing the model against a dataset of carbon dioxide release from soils, the team conducted a theoretical experiment observing how soils respond differently to plants rich in carbon versus those rich in nitrogen. Results of their study are published in the Journal of Geophysical Research: Biogeosciences.
In looking for potential ways to mitigate climate effects, some scientists are exploring how various soil inputs might increase soil’s ability to sequester carbon. Mathematical models used in making climate predictions evaluate the carbon content of soils to determine the amount released into the atmosphere as carbon dioxide. These models generally overlook the major impact microorganisms that grow in the soil, like bacteria and fungi, have on how much carbon remains in the soil and how much is released as carbon dioxide.
The new model Abramoff and colleagues developed reproduces the changing relationship between temperature and microbial respiration during the growing season to predict the rate of carbon and nitrogen cycling in the soil. Abramoff believes the new soil decomposition model could be incorporated into larger-scale models of carbon and nitrogen cycling – and effectively advance what climate predictions scientists are able to make with relation to microbial activity in soil.
“I think this model is one small step in helping scientists make better-informed predictions of the effect of climate on soils and ecosystems,” Abramoff says. “The model makes it possible to simulate the major environmental impacts to which soil might be subject: changes in temperature, changes in soil moisture, and changes that affect nitrogen inputs like fertilization or land use change.”
The new soil decomposition model was created from two simpler models. One predicts carbon dioxide release based on the amount of decomposing plant matter in relation to temperature and water content of soil. The other model also predicts carbon dioxide release from the soil, but focuses more on tracking soil carbon gains and losses by simulating decomposition of soil by microbes.
In testing the new model which combines the two, the researchers simulated how microbes would respond to soil inputs with different nitrogen content and composition. They fed the microbes two types of plants to observe the effect of priming in response to carbon-rich plants versus those rich in the nitrogen microbes need. The researchers observed that the plants with higher nitrogen content caused microbes to decompose more soil.
These observations indicate that it’s possible to inhibit soil decomposition by adding high-carbon, low-nitrogen inputs. The new soil decomposition model could also be used to test other theories about microbial activity.
Abramoff is optimistic about the potential for this model to help change the way scientists view soil microbial activity in relation to climate effects. “By taking into consideration the role of microbes in carbon dioxide release and the role of nitrogen in soil decomposition, we think this model provides a more complete picture of the various factors at play in carbon sequestration.”