解析库 > 2021年考满分GPO新题模考
Ground-level ozone, a by-product of gasoline combustion, stunts tree growth in laboratory conditions. Researchers tracked the growth rate of loblolly pine trees in a large forest in the southern United States from 1990 to 1994. Over the course of those five years, ground-level ozone in the forest increased, while the rate of circumferential trunk growth decreased. These results indicate that in nature as in the laboratory, no tree is likely to thrive in high concentrations of ground-level ozone.