PROCEEDINGS: Index of Abstracts
THE CHRONIC RESPONSE OF YELLOW-POPLAR AND EASTERN
WHITE PINE TO OZONE AND ELEVATED CARBON DIOXIDE: THREE-YEAR SUMMARY
USDA Forest Service, Northeastern Forest Experiment
Station, 359 Main Road, Delaware, OH 43015.
Abstract: The objective of this study was to determine the long-term
effects of ozone (O3) and carbon dioxide (CO2) on the growth and
physiology of eastern white pine (Pinus strobus) and yellow-poplar
(Liriodendron tulipifera) under plantation conditions. Two separate
plantations of each species were established in Delaware, Ohio,
in 1991 and 1992. Seedlings were fumigated from mid-May to mid-October
in 1992, 1993, and 1994 in standard 3m diameter open-top chambers.
The treatments, each replicated three times in a randomized block
design, included charcoal-filtered air (CF), 1X ambient O3 (1X),
2X ambient O3 (2X), 2X ambient ozone plus 350 ppm CO2 above ambient
(2X+CO2), and open-air (OA) chamberless plot. Monthly growth and
physiological measurements taken during each growing season included
stem height and basal diameter, photosynthesis, stomatal conductance,
chlorophyll content, and foliar nitrogen and phosphorus concentration.
Subsamples of yellow-poplar were destructively harvested in 1993.
First-season exposure to O3 plus CO2 appeared to have a stimulatory
effect on the growth of both species. In 1993, decreases in white
pine height growth, though not significant, were observed for both
2X- and 2X+CO2-grown seedlings. Biomass and growth stimulations
were observed on yellow-poplar in 1993, with mean increases of 14
percent in stem diameter and 16 percent in total plant height of
yellow-poplar grown in 2X+CO2 compared with all other treatments.
Although not statistically significant at p = 0.05, 2X+CO2-grown
yellow-poplar had greater leaf, stem, branch and root biomass, and
total leaf area compared with all other treatments. No significant
effects on the growth of white pine were observed. However in late
August 1994, both total height and basal stem diameter of 2X+CO2-grown
yellow-poplar were 21 percent greater than for all other treatments.
The slower growing white pine appears to be responding differently
to O3 plus CO2 than yellow-poplar.