© 1993 Heron Publishing—Victoria, Canada
The effects of acid rain and ozone on biomass and leaf area parameters of shortleaf pine (Pinus echinata Mill.)
Victor B. Shelburne, John C. Reardon and Valerie A. Paynter
Department of Forest Resources, Clemson University, Clemson, SC 29634-1003, USA / Received July 30, 1991
Summary
Shortleaf pine (Pinus echinata Mill.) seedlings in 24 open-top chambers were exposed to combinations of ozone (carbon-filtered (control), ambient, 1.7 ×
ambient, and 2.5 × ambient) and acidic precipitation (pH 5.3, 4.3 and 3.3) for 16 months (1989 harvest) or 28 months (1990
harvest). Although the effects of acid rain were generally not significant, there was a trend toward increased aboveground
biomass and leaf area in seedlings subjected to the low pH treatments. Because N concentrations in the soils generally
increased with decreasing pH, we concluded that the effects of acid rain on aboveground biomass and leaf area were a consequence
of an increasing concentration of soil N. In the 1989 harvest, seedlings in the 2.5 × ambient ozone treatment had significantly
less biomass in all aboveground plant components and significantly less total leaf area than seedlings in the 1.7 × ambient
ozone treatment. In the 1990 harvest, there were no significant effects of ozone on total aboveground biomass, although there
was a trend toward reduced biomass in seedlings in the 2.5 × ambient ozone treatment. Both total leaf area and leaf biomass
were significantly less in seedlings exposed to 2.5 × ambient ozone for 28 months than in both control seedlings and seedlings
in the 1.7 × ambient ozone treatment. The greater, but not always significant, aboveground biomass and leaf area of seedlings
in the 1.7 × ambient ozone treatment compared with control seedlings may be associated with the observed increase in soil
nitrate concentration as a result of increased rates of leaf senescence and litterfall.
Keywords:
foliage retention, foliar injury, forest decline, hydrogen ions, leaf senescence, litterfall, soil nitrogen.
