The results suggest that planting trees may not thwart global warming or serve as an adequate substitute for reducing heat-trapping greenhouse gas emissions.
Forests typically grow in poor soils.
Researchers said that once forests have initially capitalized on the extra carbon in the atmosphere, they quickly deplete nutrients in the soil. Their growth slows dramatically and their ability to store excess carbon is curtailed. As plants grow, they absorb carbon dioxide in their tissues and emit oxygen. Carbon dioxide levels in the atmosphere have been increasing for decades in conjunction with fossil fuel consumption, traffic and industrialization. Many scientists believe the rising levels of CO2 and other emissions in the atmosphere are trapping more of the sun's heat, driving up temperatures and causing global warming.