Pine, acid rain effect

Preliminary work using loblolly pine seedlings growing in sand, explored the effect of simulated acid rain on the infection of roots by ectomycorrhizae. Shafer et al. ( ) found that simulated acid rain of pH 4.0 and 3.2 was inhibiting ectomycorrhizal infection when compared to roots exposed to pH 5.6. At pH 2.4 there appeared to be stimulatory effects on infection. The authors suggested that increased soil acidity was the cause of the enhanced ectomycorrhizal infection, as other experiments have shown that, if substrate acidity is increased, so will infection. The authors did caution, however, that this short term greenhouse study was just preliminary. 

Tveite and Abraham (42) also observed a stimulation in height and diameter of Scots pine saplings when pH levels 2, 2.5 and 3.0 of simulated acid rain were supplied. There were no effects on Norway spruce or lodgepole pine. The authors suggested that the growth of Scotch pine may be due to increased uptake of nitrogen from the soil. 

Pines. Calorimetric studies of growth rates and temperature responses have not been employed to examine pine trees. Two studies were conducted to analyze effects of air pollutants on the respiration properties of Ponderosa and Jeffrey pine needles. Bower [104] used one-cm needle segments and demonstrated a correlation between the extent of ozone damage, measured as the number of lesions on the needles, and isothermal metabolic heat rates. He also measured increases in metabolic heat rates resulting from acid and nitrate deposition on the needles. Momen et al. [105] conducted a more controlled study of acid rain and ozone effects on Ponderosa pine with defined applications to plantation grown plants. In seedlings, metabolic heat rates increased in response to ozone and combinations of ozone and acid rain. Mature tree metabolic activities showed no response to ozone, acid, or combinations of the two. No studies were made to determine whether metabolic efficiencies were altered by these treatments. Thus the results show that calorimetry can be used to monitor pollutant effects on trees, but more definitive experiments must be done to identify how the ob.served responses relate to growth and survival of the trees. 

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