Effects of genotype on the response of Populus tremuloides michx. To ozone and nitrogen deposition |
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| Authors: | D F Karnosky Z E Gagnon D D Reed J A Witter |
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| Institution: | 1. School of Forestry, Michigan Technological Univ, 49931, Houghton, Michigan, USA
2. School of Natural Resources, University of Michigan, 430 University, 48109, Ann Arbor, Michigan, USA
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| Abstract: | Elevated O3 concentrations and N deposition levels co -occur in much of eastern United States. However, very little is known about their combined effects on tree growth. The effects of three O3 treatments: charcoal-filtered air, non-filtered air and O3, added at the rate of 80 ppb for 6 hr d?1 3 d per week), four N deposition levels (0, 10, 20 and 40 kg ha?1 yr?1), and their interactions on growth of two Populus tremuloides clones in open-top chambers at two sites 600 km apart in Michigan were examined. Our results revealed a highly significant fertilization effect of the N treatments, even at the 10 kg ha?1 yr?1 rate. Ozone alone induced foliar injury, but not significant growth reductions. There was an indication that O3 decreased growth at the O N level, but this decrease was reversed in all N treatments by the N fertilization effect. Further study is needed to more fully understand the combined effects of N deposition and O3. |
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