November 15, 2011
Grounded research: Prairie soil may provide answers to countering climate change
Explaining the purchase of a hundred pounds of dry ice to the authorities might be a bit awkward for some people; however, for Ari Jumpponen, associate professor of biology at Kansas State University, it's just another day as a scientist.
A $2.5 million grant, awarded by the U.S. Department of Energy to Kansas State University, Oregon State University, Lawrence Berkeley National Laboratory in California, and Oak Ridge National Laboratory in Tennessee, allows Jumpponen and his collaborators to investigate how the soil microbial community responds to changes in rainfall patterns and if that response will affect how carbon is stored and cycled in the soil.
Jumpponen uses dry ice to stop biological activity in soil samples while they are being shipped to his colleagues across the county. The dry ice keeps the soil biologically inactive so that the microbes within the soil can be analyzed as they were under the field conditions.
"We are currently trying to understand what happens to soil carbon dynamics as a result of predicted environmental change," Jumpponen said.
Soil carbon is the largest storage of carbon on land. Playing a major role in the carbon cycle known as sequestration, carbon is extracted from the atmosphere during plant photosynthesis and stored in the soil as dead plant matter, Jumpponen said. He hopes that understanding the function of soil microbes in the carbon cycle will lead to ideas to decrease atmospheric carbon.
"The more carbon we retain in the soil pools, the less there is in the atmosphere," Jumpponen said. "If we can increase sequestration and cut emissions, we might be able to counterbalance some of the on-going CO2 driven environmental change."
Soil samples are collected at Konza Prairie Biological Station, a tallgrass prairie preserve near Manhattan managed by Kansas State University's Division of Biology. The soil at Konza Prairie is rich with carbon stores, and the site has a unique rainfall alteration device known as rainfall manipulation plots, maintained as a part other extramurally funded research programs. The plots are designed to mimic current and predicted rainfall patterns that may accompany environmental changes.
"The manipulation plots are a fantastic resource, and they have allowed manipulation of one important aspect of environmental change: shifts in precipitation patterns," Jumpponen said.
Jumpponen gathers soil samples from the plots before a rain event and immediately after, which allows researchers to determine how soil organisms involved in carbon cycling may differ in their responses to rainfall.
"There is very little metabolic activity happening until we actually wet the soil; then there is this enormous increase in enzymatic activity," Jumpponen said.
Jumpponen and his colleagues look at the genes that the microbes express before the rain event and compare them to the patterns immediately after rain.
"We are trying to mine out the carbon cycling related pieces," Jumpponen said. "We are asking questions such as: In terms of the carbon cycling, what were the processes that were increased as a result of the rain pulse and how do they differ among different rain manipulation treatments?"
Two different rainfall manipulation treatments are used in this project: ambient and increased interval. The ambient allows rain to fall in a pattern and amount consistent with nature, while the increased interval plot collects rainfall, only distributing it every other time it rains naturally. Even though the plots differ in frequency of rainfall, the amount of rainfall over time is equal between the plots, Jumpponen said.
"There is a long list of carbon cycling genes that are expressed and translated into proteins in the soil," he said. "We want to actually know which ones seem to be responding to the delayed treatment in the rainfall manipulation plots. We are mostly interested in the nuts and bolts behind carbon cycling."
Jumpponen joined the university's Division of Biology faculty in 2000. He received his doctoral degree in forest science from Oregon State University in 1998.