Stories tagged prairie

Dec
08
2006


Prairie grasses: This experimental plot contains four species of prairie plants. The nearby plots, going clockwise, contain eight species, four species, and 16 species. (Photo courtesy David Tilman, University of Minnesota)

Scientists at our very own U of M have made some exciting new discoveries about the prospect of using biofuels for energy! They found that planting a diverse mix of native prairie species is more efficient than corn or soybeans, even on degraded soil. Amazingly, their most diverse plots, with 18 different species, produced 238% more bioenergy than the plots with only 1 species.

While there is still a lot of research needed to make this system useable on a wide scale, these findings are encouraging for a few reasons. Unlike all of our other forms of fuel, including corn ethanol or biodiesel from soy beans, the native plants actually absorb more carbon from the atmosphere than is released when used for fuel. Because of the vast root network associated with prairie plants (which allow them to withstand Minnesota’s hot and dry summers), much carbon is stored below ground and is not harvested for fuel. Also, these environmentally friendly crops can be grown on land that is unusable for traditional food crops. They do not need to be fertilized, a benefit to growing a native species, and thus can be grown in nutrient poor areas. Fertilizer runoff from traditional agriculture is a big contributor to water quality problems. Additionally, because native prairie species are perennial crops, they can help prevent erosion. For much of the year, particularly during the rainy months in the spring, corn or soybean fields are bare. This leaves the ground vulnerable to soil loss. Planting a native mix, particularly on steep slopes or along riverbanks, which are less suitable to traditional crops anyway, could mitigate many environmental issues. Plus, we could increase the amount of prairie habitat for native wildlife!

For more information on sustainable agriculture and the latest research check out Sustainable Agriculture Research and Education and the Minnesota Institute for Sustainable Agriculture.

Jun
07
2006


Prairie grasses: This experimental plot contains four species of prairie plants. The nearby plots, going clockwise, contain eight species, four species, and 16 species. (Photo courtesy David Tilman, University of Minnesota)

Ecosystems containing many different plant species are more productive and better able to deal with stresses such as climate extremes, pests, and disease. Those are the findings, published in last week’s issue of Nature, of University of Minnesota ecologist David Tilman and colleagues Peter Reich and Johannes Knops.

It sounds familiar, doesn’t it? The debate about whether or not diversity stabilizes ecosystems has been going on for 50 years! But Tilman’s experiment is the first to collect enough data, over enough time and in a controlled environment, to confirm the hypothesis.

Tilman, Reich, and Knops spent 12 years studying 168 9-meter-by-9-meter experimental plots at the Cedar Creek Long-Term Ecological Research (LTER) site near Cambridge, Minnesota. Each plot was randomly planted with 1-16 perennial grasses and other prairie plants. Over the 12 years of the study, temperatures and rainfall varied, but the plots with more species and more root mass did better than the others. (Why root mass? Roots store nutrients and provide a buffer against climate variations. And perennial prairie plants have far more root mass than annual plants, such as corn and other crops.)


Experimental plots: This aerial photo shows the individual nine-meter by nine-meter plots. (Photo courtesy David Tilman, University of Minnesota)

So what does it mean?

Two things. First, biodiversity does matter when it comes to healthy ecosystems. Second, biodiversity is decreasing worldwide as human populations increase and forests and prairies have been replaced with farm fields, buildings, and roads. Tilman thinks that increasing diversity may be the key to both restoring ecosystems and meeting the energy needs of people around the world.

In a National Science Foundation press release, Tilman said:

”Diverse prairie grasslands are 240 percent more productive than grasslands with a single prairie species. That’s a huge advantage. Biomass from diverse prairies can, for example, be used to make biofuels without the need for annual tilling, fertilizers, and pesticides, which require energy and pollute the environment. Because they are perennials, you can plant a prairie once and mow it for biomass every fall, essentially forever.”