Konza, June 2010

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Declining Nitrogen Indicated in Grassland Plant Specimens

Project PI: Kendra McLauchlan, Geography, Kansas State University

Scientists know that reactive nitrogen and carbon dioxide are increasing on Earth, but how that has affected nitrogen levels in plants has not been clear. Historical plant records are helping Kansas scientists gain more understanding about how nitrogen availability to grassland plants has changed over time.

This Helianthus Maximilianus (sunflower) specimen collected in 1936 was one of the 545 vascular plant specimens studied.

Kendra McLauchlan, assistant professor of geography at Kansas State University (KSU), was hired as part of the EPSCoR initiative Understanding and Forecasting Ecological Change. Her team has now studied 545 specimens of 24 vascular plant specimens collected in Kansas (predominately in Riley County) from 1876 to 2008. The specimens are catalogued in the KSU Herbarium, and data associated with them were recently digitized with the help of Kansas NSF EPSCoR funding.

The digitized data were invaluable to the researchers, as they could sift through the records much more quickly and effectively. Working with the digitized data in the Kansas State University Herbarium.The McLauchlan team’s conclusions, it turned out, were somewhat surprising. Since reactive nitrogen is increasing, the scientists hypothesized that nitrogen availability to plants would have also increased over the past 130 years. However, the leaf tissue data showed that nitrogen availability to plants has actually decreased, which is especially surprising given that there is some nitrogen pollution in the region.

Preparing specimens in the KSU Herbarium.One possible reason for the decrease is that atmospheric carbon dioxide levels are causing nitrogen levels to decrease in plants. McLauchlan’s paper on the research, “Thirteen decades of foliar isotopes indicate declining nitrogen availability in central North American grasslands” will appear in New Phytologist. She also recently received a CAREER Award from the National Science Foundation, and that funding will be used to replicate the study in other grassland areas.

Photos and specimen slide courtesy of the KSU Herbarium


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