Biodiversity Increases Ecosystems' Ability to Absorb CO2 and Nitrogen
UPTON, NY --
Biodiversity is an important factor regulating how ecosystems will
respond to increasing atmospheric carbon dioxide, say researchers from
the U.S. Department of Energy's Brookhaven National Laboratory and their
collaborators from several universities. The team of investigators, led
by Peter Reich of the University of Minnesota, just released results
from a major field study that will appear in the April 12, 2001 issue of
Nature. The scientists found that more diverse plant ecosystems were
better able to absorb carbon dioxide (CO2) and nitrogen (N), both of
which are on the rise due to human activities and industrial processes.
implication of this research is that, in response to elevated levels of
CO2 and N, ecosystems with high biodiversity will take up and sequester
more carbon and nitrogen than do ecosystems with reduced
biodiversity," says Brookhaven plant physiologist David Ellsworth,
one of the study authors.
experiment, called BioCON (Biodiversity, CO2 and N), is the first field
study to test the hypothesis that plant species diversity influences
ecosystem-scale responses to elevated CO2 and N levels. It was performed
in a scientifically controlled grassland environment at the Cedar Creek
Natural History area of the University of Minnesota, using free-air
CO2 enrichment, or FACE, technology. This experimental technology was
developed by Brookhaven National Laboratory to study the effects of
CO2 on plants in their natural environment, rather
than in greenhouses or other enclosures.
facility consists of six 20-meter diameter experimental plots, each
encircled by a ring of five-foot tall vertical pipes capable of
releasing varying concentrations of CO2. Computers monitor the wind
speed, wind direction, and CO2 level within each ring, and adjust the
release of CO2 to achieve an atmospheric concentration at a level that
is expected to occur fifty years from now.
In the BioCON
study, the six rings were each subdivided into experimental plots
measuring 2 x 2 meters. In 1997, these subplots were each planted with
either 1, 4, 9, or 16 perennial grassland plant species, randomly chosen
from among 16 species, including four nitrogen fixers. The experimental
plots within three of the rings received no additional CO2, while the
other three rings were bathed in CO2 that was about fifty percent above
the present ambient concentrations. Beginning in 1998, half the plots
received additional N, comparable to the high rates of N deposition
observed as a result of atmospheric emissions in industrialized regions.
At the end of
both the 1998 and 1999 growing seasons, the scientists measured the
total amount of plant matter (biomass) per square meter in each plot.
Biomass is an indicator of carbon accumulated via photosynthesis, the
process by which green plants use CO2, water, and sunlight to grow.
Nitrogen, an important plant nutrient, is absorbed from the soil to
become part of the biomass.
Elevated levels of CO2 and N resulted in increased biomass when compared
with plots exposed to ambient levels of CO2 and N. This effect, however,
was greatest in plots with high biodiversity as compared to those with
"These findings suggest that protecting biodiversity worldwide will contribute to safeguarding the capacity of ecosystems to capture a larger fraction of additional carbon and nitrogen entering our environment due to industrial processes," says Brookhaven ecologist George Hendrey, who led development of the FACE system and is another coauthor on the current study.
say the greater uptake of CO2 and N in biodiverse plots may be due to
positive interactions among the plant species. For example, with greater
diversity, species bloom and absorb CO2 and N over the entire growing
season, rather than just part of it.
collaborators on this study were from the University of California,
Berkeley, and the University of Nebraska. The work was funded primarily
by the U.S. Department of Energy with additional support from the U.S.
National Science Foundation.
Department of Energy's Brookhaven National Laboratory conducts research
in the physical, biomedical, and environmental sciences, as well as in
energy technologies. Brookhaven also builds and operates major
facilities available to university, industrial, and government
scientists. The Laboratory is managed by Brookhaven Science
Associates, a corporation founded by Stony Brook University and Battelle,
a nonprofit applied science and technology organization.
Note to local
editors: David Ellsworth lives in Durham, North