Study: For stable grasslands, maintain plant diversity

Cedar Creek Reserve
The University of Minnesota's Cedar Creek Ecosystem Science Reserve has been a site for scientific research for decades.
Stephanie Hemphill | MPR News

Fire, fertilizer and other human influences can hurt or help plant growth, but they only destabilize the ecosystem over time when they hurt plant diversity, according to a new University of Minnesota study.

The study, published in the journal Science, isn't the first to point out the benefits of biodiversity. But it is unique in that it combined the effects of human influences and biodiversity.

That will help researchers learn about what makes for a stable ecosystem over time, said Forest Isbell, associate director of the university's Cedar Creek Ecosystem Science Reserve, where the data from grassland plots was collected over 28 years.

Cedar Creek contains several different types of natural ecosystems, including grasslands, bogs and forests. Scientists have been conducting experiments there for decades.

"The interesting thing here is these different [human] manipulations only impacted the stability of plant growth over time when they impacted biodiversity," Isbell said in an interview.

Plant diversity can help stabilize an ecosystem, he said.

"There are some plant species that do well during dry years, others that do well during wet years, some that do well under fire conditions and others that do well without burning," he said. "Different species take turns in different years, essentially."

While the study did not look at agricultural plots, Isbell said the findings could have important implications for agriculture. In the past, the strategy for agriculture has been to find the best plant variety overall — the one that is most likely to succeed given unpredictable conditions. But some companies are changing strategies in favor of boosting diversity in cropping systems so that no matter the conditions, yields will be relatively consistent, Isbell said.

"It's hard to know whether there will be a drought this year coming up, but we still have to plant something now," he said. "This diversity is becoming something that's increasingly appreciated as something that can help us hedge our bets against unpredictable environmental variability."

The study was led by Yann Hautier, a research fellow with the University of Minnesota and the University of Oxford in the U.K.

"Biodiversity is somehow a special case, because it's not only a cause of changes in ecosystems but also a response to other changes," Hautier said in a news release. "The main message is that if we want to continue to benefit from the services that our ecosystems are providing, we should be very careful about preserving biodiversity."

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