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Growth Fluctuation of Loblolly Pine Due to Periodic Air Pollution Levels: Interaction of Rainfall and Age. S. O. Phillips, Former Graduate Research Assistant, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, Senior author current address: Special Projects Forester, Missouri Department of Conservation, Columbia, MO 65201; J. M. Skelly(2), and H. E. Burkhart(3). (2)(3)Associate Professor in the Department of Plant Pathology and Physiology, and Associate Professor in the School of Forestry and Wildlife, respectively, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061. Phytopathology 67:716-720. Accepted for publication 21 December 1976. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-716.

The effect of a periodic source of a NOx-SO2 air pollution regime on the growth of loblolly pine was investigated. Radial increment growth studies were conducted to determine if correlations existed between emission levels (predictions of production levels were used as a surrogate) of a source and radial increment growth of loblolly pine. Three stands of loblolly pine proximal to the emission source were sampled by obtaining breast-height (1.37 m above the base of the tree) increment cores from 50 trees in the dominant or codominant crown classes of each stand. Multiple linear regression analyses utilizing annual radial increment growth as the dependent variable and the independent variables of annual production levels, total annual rainfall, annual seasonal rainfall, and age were used to evaluate radial growth of sample trees within all stands. An inverse relationship significant at P = 0.01 was demonstrated between growth and production levels in two of the loblolly pine stands. Additional analyses of these stands indicated theoretical reductions in diameter growth within both stands without the presence of visible injury. Growth and production levels were not significantly correlated in the remaining loblolly pine stand.

Additional keywords: tree growth loss, sulphur dioxide, nitrogen oxides, Pinus taeda.