101017_Konza

Konza Praire

The economically important big bluestem grass — a dominant prairie grass and a major forage grass for cattle — is predicted to reduce its growth and stature by up to 60 percent in the next 75 years because of climate change, according to a study involving Kansas State University researchers.

The group of scientists, which included collaborators at Missouri Botanical Garden and Southern Illinois University, Carbondale, has published the study in the peer-reviewed journal Global Change Biology. Kansas State University researchers involved include Loretta Johnson, professor of biology; Mary Knapp, associate agronomist and state climatologist; and Jacob Alsdurf, master’s student in biology, Olathe. The paper is a culmination of several years of close collaboration and interdisciplinary studies, including species modeling, plant growth studies and climatology.

Big bluestem is a common grass in natural and restored prairies across the central Midwestern region that includes Kansas, Nebraska, Oklahoma, Missouri and Iowa. The grass species is an important component of forage for the region’s livestock industry. It also is commonly used in grassland restoration of prairies across several million acres in the Great Plains region.

“Our results predict that climate change could greatly impact the tallgrass prairie as we currently know it, reducing forage for cattle in the drier parts of grasslands, in places like Kansas,” Johnson said.

In the Midwest, big bluestem can grow from 4 to 6 feet tall, but the researchers found that climate change could reduce its height by up to 60 percent in the next 75 years. As a result, the form of big bluestem that grows in the central Midwest could come to resemble the form that currently inhabits eastern Colorado on the edge of the species’ range. The tall forms of the Midwest grass could shift to the Great Lakes region where big bluestem is currently less common.

The research team found that most of the change was because of alterations in rainfall that are expected to occur across the area, not because of increases in temperature.

The authors are concerned the dramatic reduction in size of big bluestem foretells a fundamental shift in the nature of the Midwestern grassland ecosystem.

“Because big bluestem is currently a dominant grass species of the Great Plains and makes up to 70 percent of the plant biomass in places, how the ecosystem works could be affected by predicted changes in growth of this species,” Johnson said.