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.”

Your Comments, Thoughts, Questions, Ideas

Liza's picture
Liza says:

Curious about what goes on at Cedar Creek? They offer public tours on the second Saturday of each month, May through October.

The June 10th tour group will visit the Cedar Creek prescribed burns and Allison Savanna:

Explore the rolling topography of Allison Savanna, a Scientific and Natural Area right at the south-east corner of the Cedar Creek area. This was an early acquisition of the Nature Conservancy and remains one of the best tracts of the vanishing bur oak savanna in our state. Large-flowered Beardtongue should be in full flower and busy with bees. Also sandy blowouts will be alive with the activities of tiger beetles, velvet ants, and spider wasps. Dung beetles should be rolling deer pellets. Contrast Allison Savanna with the prescribed burning units across the road on Cedar Creek, and learn about the benefits of fire in savanna ecosystems.

You don't have to register in advance, but calling ahead helps the staff plan for the right number of people. (763-434-5131)

Get directions and further information from the website.

posted on Wed, 06/07/2006 - 3:14pm

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