Elevated Carbon Dioxide Has Uneven Influence on
Longleaf Communities By
Laura McGinnis December 11, 2007
No plant is an island. That's one conclusion of a global change study
conducted by Agricultural Research Service (ARS) scientists at the
Dynamics Research Unit in Auburn, Ala.
The researchers found that carbon-dioxide-induced changes to longleaf
pine communities could lead to competitive displacement and the gradual
elimination of species that currently thrive there.
Led by plant pathologist
Brett Runion and plant physiologists
A. Prior and
Rogers, the team investigated the response of longleaf pine communities to
the doubled atmospheric carbon dioxide (CO2) levels projected to occur within
They compared the growth rates of longleaf pine and four southeastern
plant species that often grow in the same environment after three years of
exposure to either ambient or elevated CO2. Within the simulated plant
communities, species responses varied significantly.
Longleaf pine savannas account for about 3.7 million acres of the
southeastern United Statesabout 4 percent of their original range.
However, they remain an influential part of the southeast landscape. The pines
are highly resistant to many insects and diseases that harm other southeastern
pines. Plus, longleaf communities support several endangered species, including
red cockaded woodpeckers and gopher tortoises.
The scientists were surprised to observe that after three years,
longleaf pines exposed to higher CO2 were more than five feet tall on
averagenearly two feet taller than the control group.
The total biomass of the plants exposed to elevated CO2 was 70 percent
greater aboveground and 49 percent greater belowground than that of the
control. However, growth rates were not universal. While longleaf pines shot
up, wiregrass, rattlebox and butterfly weed actually decreased in
biomass, and sand post oak had no significant growth response.
These responses affected the plant community's composition. Longleaf
pine accounted for 76 percent of the total biomass in ambient CO2 plots, but
made up 88 percent of the elevated CO2 plots. Wiregrass, rattlebox and
butterfly weed dropped from 19 percent of the ambient plots to 8 percent of the
elevated CO2 plots.
ARS is the U.S. Department of
Agricultures chief in-house scientific research agency.