A dendroclimatological correlation of white pine radial growth with ozone levels over time at Acadia National Park

Bartholomay, G.

Project was initiated to 'investigate the association between ozone levels recorded in Acadia National Park and white pine radial growth. Dendroclimatological techniques are used to correlate annual ring widths with climatic variables (precipitation, temperature) and ozone variables. Factors affecting photosynthesis ultimately affect radial growth because up to 45% of the carbohydrates produced through photosynthesis are assimilated into wood cells (Creber and Chaloner, 1984). If ozone levels are affecting the physiological processes of white pine, these effects will likely be recorded as variations in the width of the trees' annual growth rings.' Project objectives include: '1) create stand level radial growth models for eight individual stands of white pine, incorporating monthly precipitation, monthly temperature and several measures of ozone exposure from 1983 through 1992. 2) create a regional radial growth model which combines several white pine tree-ring series from each of the eight stands, utilizing the previously mentioned climate and ozone variables from 1983 through 1992. 3) describe, at the regional level, the dynamic relationship between white pine radial growth and monthly climate variables (precipitation and temperature) from 1900 through 1992.' Concludes that: 'White pine radial growth was found to be inversely related to ozone level and duration of exposure. Tree-ring chronologies from seven out of eight stands and the regional chronology were all significantly correlated with ozone levels. Only one of the eight stands (stand 2) lacked a significant correlation between tree-rings and ozone levels. Climate is usually expected to account for 30% to 40% of the variation in tree-rings in temperate climes. The significant regression models in this study explained 67% to 98% of the variation in tree-rings from 1983 through 1992 (Table 3) suggesting that ozone pollution at Acadia National Park has a stronger influence on tree-ring growth than does climate. Specifically, short duration high level ozone events were found to have the greatest negative relationship with tree-rings.' 'Tree growth and ozone relationships were also found to differ from stand to stand. This suggests that site characteristics play an important role in how trees respond to ozone pollution. It can be inferred that smaller forest units respond differently than entire forest regions. This finding is similar to a study by Lane and others (1993) that found sugar maple growth - climate relationships are dependent upon site.' 'A regional de-coupling of the growth - climate correlation was not evident in this study. Many of the tree-ring series used to construct the regional chronology contained more than 100 years of growth with 40% of the cores contained more than 51 years of growth. It may be that these trees are able to adapt to long term environmental changes. As such, they may be less readily affected by changing ozone levels and will not display a distinct change in their radial growth - climate relationship. A prolonged increase in ozone levels over time may not cause a distinct change in the growth trend but may cause a more subtle change that cannot be detected by the methods employed here.' 'It should be noted that this study is based on correlative data. The results are observed associations and do not constitute cause and effect relationships. There is, however, a strong correlative association between white pine radial growth and ozone levels over time. This finding warrants further research to determine the mechanism that underlies this association.'