THE IMPACT OF OZONE AND ACID MIST ON THE SPECTRAL REFLECTANCE OF YOUNG NORWAY SPRUCE TREES

Spectral reflectance curves in the 400-1110 nm range have been obtained from two-year-old Norway spruce seedlings exposed to varying levels of ozone and acid mist during their two years of growth in controlled environmental chambers. The trees were exposed to 100 ppb ozone, 140 ppb ozone and 140 ppb ozone plus acid mist, while the control group were exposed to filtered air. Two spectral parameters are used to indicate the impact of these pollutants, namely the level of the infrared plateau and the position of the red edge. The infrared plateau has been found to have a higher reflectance as pollutant concentrations increase. This is thought to infer changes within the internal structure of the leaves. The red edge has been found to shift by up to 18 nm at the point of maximum red-edge slope. From both these parameters it is apparent that damage from ozone levels of between 100 and 140 ppb is detectable. This is especially so when the plants are concurrently exposed to acid mist.