Author： McLaughlin S. B. McConathy R. K. Duvick D. Mann L. K.
Publisher： Society of American Foresters
ISSN： 0015-749X
Source： Forest Science, Vol.28, Iss.1, 1982-03, pp. : 60-70
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Abstract
Comparisons of annual growth, photosynthetic capacity, and fate of photosynthetic products were made to determine the rate and cause of declining vigor of oxidant-stressed white pine (Pinus strobus L.) growing near Oak Ridge, Tennessee. Three approximately 25-year-old trees were selected for study from each of three sensitivity classes based on needle color, length, and duration of retention. Growth ring analysis revealed comparable growth trends in intermediate and tolerant trees whereas sensitive trees experienced a steady decline in average ring width (70 percent decrease over 15 years) and a loss in capacity for recovery of growth. The fate of photosynthetically fixed 14C was followed after supplying 14CO2 to in situ foliage four times (June, July, August, November) during the growing season. Carbon-14 transport patterns emphasized the role of older needles as sources of photosynthate for new needle growth in spring and storage sinks in the fall. Higher retention of 14C-photosynthate by foliage and branches of sensitive trees indicated that photosynthate export to boles and roots was reduced. Photosynthetic capacity (CO2 uptake/g dwt) of foliage of sensitive and tolerant trees was similar. The ratio of respiratory to photosynthetic activity was significantly higher for foliage of sensitive trees. Results suggest that declining vigor of sensitive trees in this area results from reductions in needle longevity, size, increased respiratory activity, and altered translocation patterns which are induced by chronic air pollution stress. Forest Sci. 28:60-70.
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