Effects of Filtered Air and Misting Treatments on Cuticles of Red Spruce Needles on Whiteface Mountain, N.Y.

Abstract

wo sets of large (8-20 m tall) red spruce (Picea rubens Sarg.) trees growing on Whiteface Mountain, N.Y., were used in branch chamber experiments. In the summer of 1988, the treatments were made on four healthy trees and consisted of: (1) open branches (N), and in chambers that were supplied with either: (2) ambient air (A); (3) charcoal-filtered air (T); or (4) charcoalfiltered air and deionized water misting when the forest was immersed in ambient cloud water (M). Each tree had all of the treatments. The treatments for the second year (summer of 1989) were made on four declining trees and consisted of: (1) open branches (NC) and chambers supplied with either (2) ambient air and mist (AA), (3) synthetic acid mist and ambient air (SA), (4) distilled water mist and ambient air (DA), (5) synthetic acid mist with filtered air (SF), and (6) distilled water mist with filtered air (DF). Foliar properties measurcd included: (1) microreflectivity, a measure of surface wax properties; (2) cuticle thickness; (3) cutinized cell wall thickness; (4) total cuticular layer thickness: (5) the mass of surface wax extracted from needle samples; and (6) contact angles, a measure of surface wetting. In addition, needles were collected and measured from healthy trees at lower and higher elevations. In the first experiment, reflectance from the wax in the stomata1 antechambers in treatment M was statistically significantly greater than all the other treatments. The cuticles of needles in treatment M were also statistically significantly thicker than the cuticles measured in all the other treatments (40% thicker than for the open branches). A plot of cuticular layer against elevation showed that the two filtered chambers (M and T) provided environments for cuticle development that mimic lower elevations. In 1989 the weather was cooler and more moist, and although the trees used in 1989 were declining, the results were similar to those of 1988. However, the additional treatments with synthetic acid mist resulted in reduced cuticle thickness. While the cuticles of the chamber trees growing at 1,170 m were, except for treatment M and T, generally thicker in 1989 than in 1988, they were still considerably thinner than those of spruce trees growing at the lower elevations. These results suggest regional scale air and precipitation quality have detrimental effects on red spruce needles at Whiteface Mountain.