Elevated carbon dioxide boosts biomass growth in longleaf communities, but displaces other species
Scientists from the U.S. Agricultural Research Service's (ARS) Soil Dynamics Research Unit have found that when longleaf pine trees are exposed to elevated levels of carbon dioxide their total biomass production receives a spectacular boost. After doubling ambient CO2 levels, aboveground biomass increased by 70% and belowground levels increased by 42%. But the researchers also observed that the faster growing trees displaced other plant species, thus changing the plant community's composition. The findings have relevance to bioenergy, as elevated CO2 levels could stimulate plant growth (even though many other factors may cancel out this effect).
The findings were obtained during a Global Change study conducted by led by plant pathologist G. Brett Runion and plant physiologists Stephen A. Prior and Hugo H. Rogers. The team investigated the response of longleaf pine communities to the doubled atmospheric carbon dioxide levels projected to occur within this century.
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 States—about 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 only after three years, longleaf pines exposed to higher CO2 were more than five feet tall on average — nearly two feet taller than the control group:
energy :: sustainability ::biomass :: bioenergy :: biofuels :: carbon cycle :: carbon dioxide :: climate change :: biodiversity ::
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.
In a similar project, Brett Runion is studying the effects of rising atmospheric carbon dioxide concentration on crop and pasture production and the role of agronomic ecosystems in the sequestration of atmospheric carbon dioxide as organic carbon in soils, as well as the release of carbon dioxide and other greenhouse gases from soil, as affected by agricultural management practices.
Specifically, the project will determine the effects of carbon dioxide on belowground processes which affect crop productivity, soil physicochemical/biological properties, carbon/nutrient cycling, and trace gas efflux from soil.
ARS is the U.S. Department of Agriculture’s chief in-house scientific research agency.
Picture: Longleaf pines and other plants grow in an 8-foot tall open-top field chamber. Exposed to elevated levels of CO2, pines in the chamber grew faster than pines grown in ambient CO2. Credit: Barry Dorman, ARS.
References:
National Soil Dynamics Laboratory: Global Change and Belowground Processes in Agricultural Systems.
USDA ARS: Elevated Carbon Dioxide Has Uneven Influence on Longleaf Communities - December 11, 2007.
The findings were obtained during a Global Change study conducted by led by plant pathologist G. Brett Runion and plant physiologists Stephen A. Prior and Hugo H. Rogers. The team investigated the response of longleaf pine communities to the doubled atmospheric carbon dioxide levels projected to occur within this century.
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 States—about 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 only after three years, longleaf pines exposed to higher CO2 were more than five feet tall on average — nearly two feet taller than the control group:
energy :: sustainability ::biomass :: bioenergy :: biofuels :: carbon cycle :: carbon dioxide :: climate change :: biodiversity ::
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.
In a similar project, Brett Runion is studying the effects of rising atmospheric carbon dioxide concentration on crop and pasture production and the role of agronomic ecosystems in the sequestration of atmospheric carbon dioxide as organic carbon in soils, as well as the release of carbon dioxide and other greenhouse gases from soil, as affected by agricultural management practices.
Specifically, the project will determine the effects of carbon dioxide on belowground processes which affect crop productivity, soil physicochemical/biological properties, carbon/nutrient cycling, and trace gas efflux from soil.
ARS is the U.S. Department of Agriculture’s chief in-house scientific research agency.
Picture: Longleaf pines and other plants grow in an 8-foot tall open-top field chamber. Exposed to elevated levels of CO2, pines in the chamber grew faster than pines grown in ambient CO2. Credit: Barry Dorman, ARS.
References:
National Soil Dynamics Laboratory: Global Change and Belowground Processes in Agricultural Systems.
USDA ARS: Elevated Carbon Dioxide Has Uneven Influence on Longleaf Communities - December 11, 2007.
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