PULLMAN, Wash. — In a Nature magazine article to be published today, Richard Gill, a Washington State University assistant professor of environmental science, contends that ecosystems are reaching their limit as sinks for excess greenhouse gases.

Gill’s research on how ecosystems respond to changes in carbon dioxide, the most abundant greenhouse gas, is being conducted at a tallgrass prairie field site at a U.S. Department of Agriculture crop lab near Temple, Texas.

“Carbon dioxide has been increasing in the atmosphere for the last 10,000 years. This increase has been especially rapid in the last 150 years because of the industrial revolution and the conversion of land to agricultural uses. However, the rate of increase has been slowed because some of the carbon has been stored in organic matter in the soil moderating increases in atmospheric carbon dioxide. However, the storage capacity is dependent on how both plants and soils respond to the changes caused by the rising carbon dioxide. Increased carbon dioxide tends to make plants more productive, but their productivity begins to create problems in the soil.

“Our research shows that there is a limit to how much carbon can be stored in soils. In the past, soils have played an important role in keeping carbon dioxide out of the atmosphere, but we may be at an important threshold. In this prairie soil, we saw that at high carbon dioxide concentrations, soils were not able to continue to store excess carbon. It appears that soil carbon storage is very sensitive to nitrogen availability–which changed dramatically with rising carbon dioxide,” he said.

“There are important implications for these results. In the past, greenhouse gasses have not accumulated in the atmosphere as fast as we were producing them because natural systems were absorbing some of the extra carbon dioxide. However, if the ability of soils to continue to absorb carbon dioxide is limited, we may soon begin to see rapid increases of greenhouse gasses in the atmosphere, leading to potentially swift changes in global climate. There are indications that the interaction between plants and soils could also limit the ability of forests and croplands to absorb the excess carbon as well. ”

The Nature magazine article is titled “Nonlinear Grassland Responses to Past and Future Atmospheric CO2..” Gill’s research is funded by a United States Department of Agriculture National Research Initiative Program grant. He joined the WSU faculty last fall. Previously he earned a doctorate at Colorado State University and completed post-doctoral studies at Duke University.