Tree damage following dust abatement/road stabilization treatment was evaluated on 12.5 miles of the Selway River Road, Nez Perce National Forest. Calcium chloride was applied in June of 2000, mostly at a rate of 51b/yd2 (18,600 lb./acre) or 6.9 lb/yd 2 (25,700 lb/acre). 1,189 trees up to 30 feet from the road were examined in June 2001 and again in December 2001. Western redcedar and Douglas-fir were most damaged by the chloride. Ponderosa pine was the most tolerant of the tree species. Severity of damage was associated with tree species, proximity of trees to road, and CaCl2 application rates. Cedar foliage samples collected in November 2001 from symptomatic trees near treated road averaged nearly seven times more chloride ion concentration than the controls. Treated Douglas-fir averaged 50 times more and ponderosa pine average 30 times more than their respective controls. As of December 2001, 12% of cedars were dead and another 18% appear to be dying. Douglas-fir fared worse with 29% dead and 12% dying. Grand fir and ponderosa pine had only 6% and 4%, respectively, dead or dying.
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