ANATOMICAL EVIDENCE OF THE DEVELOPMENT OF DAMAGE SYMPTOMS ACROSS A GROWING-SEASON IN NEEDLES OF RED SPRUCE FROM CENTRAL NEW-HAMPSHIRE

An anatomical assessment was conducted on first-year red spruce needle s collected over two entire growing seasons from mid- and high-elevati on trees for the purpose of identifying specific cytological changes a ssociated with forest decline. Multiple collections for anatomical eva luation were made over the 1988 and 1989 growing seasons from selected trees at two sites on Mt. Moosilauke, NH: a high-elevation site at 96 0 m elevation, characterized by red spruce trees exhibiting chlorosis and evidence of foliar loss, and a mid-elevation site at 790 m elevati on, characterized by red spruce exhibiting no forest decline symptoms. The high-elevation site was adjacent to an atmospheric monitoring sta tion which measured and recorded atmospheric parameters including trop ospheric ozone levels and cloud event occurrence and chemistry. Collec tions of first-year needles from each of nine trees (five trees at the mid-elevation site and four at the high-elevation site) were made. Th e first collection was made within 1 week of completion of branch expa nsion and flush of 1988 and 1989 needles, followed by four additional collections across the 1988 growing season. A total of eight collectio ns were made over the 1989 growing season. For 1988, at the mid-elevat ion site, cytological changes that occurred over the growing season in the mesophyll cells were typical of normal developmental patterns. At the high-elevation site the mesophyll cells of needles exhibited a pr ogressive development of cytological damage symptoms including: plasmo lysis; granular, dark-staining cytoplasmic or vacuolar contents; loss of discrete chloroplasts; cell wall thickening and increased occurrenc e of vacuolar crystals. For 1989, similar developmental patterns were seen at both sites across the growing season, but followed a different temporal pattern when compared with 1988. The severity of cytological damage at the high-elevation site was less at the end of the 1989 gro wing season. The most severe cytological damage was seen at the high-e levation site 10 days following a low pH cloud event that occurred on September 20, 1988. A similar increase in damage symptoms did not occu r at the mid-elevation site following that event. The evidence present ed supports the view that increases in cytological damage in first-yea r needle mesophyll occurred across both growing seasons at the upper-e levation site, possibly in response to exposure to elevated levels of ozone and to low pH cloud events. This cytological damage developed pr ior to the onset of winter at the upper-elevation site in both 1988 an d 1989. (C) 1998 Elsevier Science B.V. All rights reserved.