The Impact of an Urban-Industrial Area on Deciduous Forest Tree Growth1
- J. R. Mc Clenahen2
Factors affecting the height-growth of white ash (Fraxinus americana L.) and northern red oak (Quercus rubra L.) trees in natural stands were studied within the airshed of an industrial city in central Ohio. Stepdown multiple regression analysis was used to determine the effect of tree age, topography, precipitation, and physical and chemical soil properties on cumulative height-growth between 1930–76, which included an era of major urban and industrial expansion. Expressions of distance from the city and an index of relative pollutant exposure (RPE), derived in part from the frequency of airflow from the city during the growing season, were also tested as independent variables indicative of relative pollutant dose. Eleven and thirteen significant variables in the final white ash and red oak models explained 63 and 93% of the variation in height-growth, respectively. Distance from the city and RPE were significant in the models of both species. Significant interactions of these variables with tree age indicated that growth of youngered oaks was more strongly depressed by increasing RPE than was that of older trees; growth of younger, but not older, white ash increased with distance from the city. Red oak growth was unexplainably predicted to be greater nearer the city. Holding tree age and site variables at their means, height-growth was estimated by the regression models for actual RPE at selected distances and directions around the city. Isopleths constructed from these estimates showed an area of reduced growth northeast of the city in the prevailing wind direction for both species. It appears from this study that height-growth of forest trees can be measurably depressed as a result of urban influences probably relating to air pollutant exposure.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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