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Prairie
plants may also be good source of biofuel
Ecosystems
With Many Plant Species Produce More and Survive Threats Better
May 31, 2006
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This
experimental plot is planted with four species of flowering
prairie plants known as forbs. The adjacent plots, in
clockwise rotation, are planted with eight species, four
species and 16 species.
Credit: David Tilman, UMN
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Ecosystems containing many
different plant species are not only more productive, they are
better able to withstand and recover from climate extremes, pests
and disease over long periods, according to a new study. It is
the first experiment to gather enough data--over a sufficient
time and in a controlled environment--to confirm a 50-year
scientific debate about whether biodiversity stabilizes
ecosystems.
The findings, published in this
week's issue of the journal Nature,
are the result of 12 years of experiments conducted by David
Tilman, an ecologist at the University of Minnesota, and
colleagues Peter Reich of the University of Minnesota and
Johannes Knops of the University of Nebraska. The research was
conducted at the Cedar Creek Long-Term Ecological Research (LTER)
site, one of 26 such National Science Foundation (NSF) sites.
"This study clearly
demonstrates that stability of a plant community through time
increases as species richness goes up," said Martyn
Caldwell, program director in NSF's Division of Environmental
Biology, which funded the research. "Only a long-term field
experiment can provide this information."
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Individual plots
in this aerial view of the plant biodiversity experiment are
9 meters by 9 meters.
Credit: David Tilman, UMN
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Biodiversity of global
ecosystems has decreased as global population has increased, said
Tilman, because diverse ecosystems such as forests and prairies
have been cleared to make way for agricultural fields, buildings
and roads.
The research shows that
ecosystems containing many different plant species are more
productive than those containing only one species. A return to
biodiversity may prove to be the key, Tilman and his colleagues
believe, to meeting energy needs for the growing number of people
on the planet and for restoring global ecosystems.
"Diverse prairie
grasslands are 240 percent more productive than grasslands with a
single prairie species," Tilman said. "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,"
Tilman said.
The research was carried out in
168 plots, each of which was randomly planted with one to 16
perennial grasses and other prairie plants. Stability of plants
in the plots depended upon diversity and root mass. Roots store
nutrients and buffer against climate variations. Perennial
prairie plants have far more root mass than crops such as corn,
which must be replanted annually.
Source
/ Credit: NSF
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