Regional Tree Growth Reductions due to Ambient Ozone: Evidence from Field Experiments

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Observations from extensive regions in Europe and North America suggest that many forests may be in early stages of ecosystem decline. We present experimental evidence from open-top chamber field studies indicating that ambient ozone at levels below the ambient air quality standard (235 μg m-3) causes significant reductions (19%) in the growth of sapling poplars (hybrid Populus). While ozone-induced reductions in growth have been observed under laboratory and greenhouse conditions, demonstration of this effect under field conditions is critical to the establishment of ozone standards. Growth reductions for Populus deltoides and Robinia pseudoacacia were not significant (α = 0.05). Reductions in productivity and height growth occurred without visible symptoms of foliar injury and at ozone concentrations below current standards. If this “invisible” injury is typical in other tree species, the extent of ozone-induced forest damage may presently be greatly underestimated. Additional field studies on a regional basis are needed. © 1986, American Chemical Society. All rights reserved.

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Environmental Science and Technology