Grasslands, Carbon Storage and Biodiversity

Environmental & Science Education, STEM, Climate Change, Biodiversity, Nature, Sustainability, global Change

Ed Hessler

University of Minnesota research conducted at the Cedar Creek Ecosystem Science Reserve has shown "that the degree of biodiversity in the world's grasslands is vital to their ability to continue functioning as carbon 'sinks'".

Deane Morrison reports on the work of a then PhD student (now a postdoctoral student at the University of Vermont), Melissa Pastore. She was advised by Professor Sarah Hobbie, College of Biological Sciences (CBS) and Regents Professor Peter Reich, College of Food, Agricultural and Natural Resource Sciences (CFAN).

Four grassland plots, "either with one, four, nine, or 16 species of plants" were studied Some of the plots were treated with CO2 at levels likely to occur at the end of the century. Some plots received standard nitrogen fertilizer at rates of current nitrogen deposition the Northern Hemisphere. Other plots received both treatments or neither. Additionally, they were also periodically burned with scheduled prairie fires.

And this is what the researchers found."On average over 19 years, increasing the species richness from one species to four, nine, or 16 boosted total carbon storage by 22 to 32 percent. But even though the soil was nutrient-poor, the added nitrogen and CO₂ increased carbon stores by only about 5 percent. Soil carbon—which excluded any in above ground plants and roots down to 20 centimeters—accounted for 90 percent of total ecosystem carbon. Therefore, as soil carbon went, so also did ecosystem carbon."

There is a caveat. The treatments raised carbon loses. Those plots treated with nitrogen and CO2 "enhanced plant growth--barely outweighing the losses. The plots with more species both gained and lost more soil carbon "but the gains outstripped the losses by large enough margins that carbon storage rose by a substantial amount."

Currently, some models overestimate carbon storage as atmospheric CO2 increases, not taking richness of species into account. The key to soil storage of carbon is grassland biodiversity, at least maintaining it where it exists.