Acid Fog, Ozone and Low Elevation Spruce Decline

Publisher Website
Google Scholar
Abstract
A recently discovered decline of red spruce (Picea ntbens Sarg.) is described for coastal Maine, U.S.A. The symptoms include chlorosis of adaxial needle surfaces, progressive loss of needles (from oldest to youngest) and development of latent vegetative shoots on dorsal surfaces of declining branches. Symptoms are most prominent in trees growing in thin organic soils on granite bedrock where ozone levels are highest and fog pH values are lowest. On sites where fog is less acidic spruce decline has not been observed. Stern cores from 30 trees (two cores per tree) were analysed from each of three sites: Head Harbor, Eastern Head and Roque Island. Head Harbor has trees showing severe decline symptoms and receives ozone levels as high as 0.14 ppm and fog acidities as low as pH 2.9. The soil is thin over granite outcropping. At Eastern Head (less than 1 kilometer away) fog pH and ozone levels are the same, but soils are deeper and exposure is different. Decline symptoms are barely noticeable. At Roque Island the soils are similar to those at Head Harbor but ozone levels are somewhat lower and minimum fog pH values are above 3.3. Two different tree ring measures suggest that Eastern Head and Roque Island have similar site indices for red spruce growth while Head Harbor is poorer. Tree ring analysis revealed that the years 1955-75 were ideal for growth on these sites but many Head Harbor trees began declining in radial increment near the beginning of this period. During the past 15 years average radial increment at Head Harbor was 0.86 mm/year while at Roque Island it was 2.48 mm/year. Although very little visible decline can be seen at Eastern Head, average radial increment for the past 15 years at this site has been only 1.61 mm/year.

This publication has 0 references indexed in Scilit: