Assumptions of Effects of Rising Carbon Dioxide Probed

How will rising levels of carbon dioxide influence ecosystems? Scientists have tackled this question numerous times, but none have tested the assumption that a single-abrupt increase in CO2 concentrations will produce changes similar to gradual increases over several decades. UCR scientist part of research team published in the journal Nature.

A paper in the Feb. 10 issue of the journal Nature titled Abrupt Rise in Atmospheric CO2 Overestimates Community Response in a Model Plant-Soil System, takes a closer look at this aspect of climate modeling. University of California, Riverside Professor of Plant Pathology and Biology, Michael Allen is part of the research team that wrote the paper with John N. Klironomos, Shokouh Makvandi-Nejad, Benjamin E. Wolfe, and Jeff R. Powell of the Department of Botany, University of Guelph, Ontario, Canada; and Matthias C. Rilling and Jeff Piotrowski of the Division of Biological Sciences, University of Montana. The work was supported by the Canadian Government, the U. S. Department of Energy, and the U. S. National Science Foundation.

The team observed the response of a mycorrhizal fungal community to CO2 concentrations over a span of six years, which included 21 generations. The fungi, which live around the root systems of plants, are considered a beneficial partner to plants – helping them cope with natural stresses, such as low soil fertility, drought and temperature extremes.

The fungi were exposed to either an abrupt or gradual increase in this atmospheric gas. The group exposed to a slow rise in CO2 concentration showed less of a decline in the number of species per sample – a standard ecological measure of biodiversity – of the fungi than did the group exposed to the abrupt change, but the difference was not significant.

The findings suggest that previous work has overestimated the magnitude of community and ecosystem responses to carbon dioxide changes, the researchers say.

The study fulfills a goal in the larger body of climate change research to predict how ecological systems will function and be structured in the future, when the climate is expected to be significantly different from what it is today. Atmospheric CO2 is expected to continue rising during the next century to concentrations of 550 parts per million, significantly greater than today’s concentrations of almost 370 p.p.m. A major research effort is under way to understand the changes that will occur to population, community and ecosystem structures, and functions in response to these expected CO2 increases.

“Climate change is one of several potential responses of the rapidly escalating atmospheric CO2. Subtle ecosystem responses ranging from reduced plant nutrition to increasing crop pest activity are also postulated,” said Allen. “Our research demonstrates that communities of organisms can adjust to shifting conditions, and points to the need for careful experiments that study dynamics of our environment integrating time if we are to predict what factors will be of concern to the future health of our cropping and wildland ecosystems.”

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