Worldwide Study: Fertilizer Destabilizing Grasslandsselfnews Post More nitrogen means more production, but its less stable, said Johannes M.H. Knops, a University of Nebraska-Lincoln biologist and one of the papers international co-authors. There are more good years and more bad years. Not all years are going to be good and the bad years are going to be worse. The three-year study monitored real-world grasslands at 41 locations on five continents. The sites included alpine grasslands in China, tallgrass prairies in the United States, pasture in Switzerland, savanna in Tanzania and old fields in Germany. Two sites in Nebraska were part of the study, the Cedar Point Biological Station near Ogallala and the Barta Brothers Ranch in the Sandhills near Valentine. While public attention has grown about elevated levels of carbon dioxide and global warming, Knops said elevated levels of mineral nitrogen in the environment also are concerning. While its rare for ranchers and farmers to fertilize rangeland and pasture, grasslands are affected by nitrogen deposition that results from burning fossil fuels, as well as from fertilizer runoff and ammonia volatilization from cropland. Knops said fertilizer overuse could intensify the detrimental effects of drought on grasslands, such as the drought that devastated cattle herds in Texas and Oklahoma from 2011-13, when Texas lost about 15 percent of its cattle herd, or about 2 million animals. It also could have ripple effects during bad years by reducing the plant cover, which increases erosion, and decreases water filtration and carbon sequestration benefits provided by grasslands. The Nature article, Eutrophication weakens stabilizing effects of diversity in natural grasslands, is one of several research articles on the relationships between grassland diversity, productivity and stability, generated by the Nutrient Network experiment. Knops called it an unprecedented experiment. In the past you didnt see a collaborative effort at a really large scale like this in biology or in ecology, he said. For more information about the Nutrient Network effort, visit http://www.nutnet.org 