The assessment and condition of Fundy white birches in relation to ambient exposure to acid marine fogs

The condition of white birches within 30 km of the Bay of Fundy, New Brunswick, have been monitored by the Canadian Forest Service since 1981, when an apparent deterioration in their condition and foliar browning was noticed. The apparent lack of associated insects or diseases that could have caused this change led to an investigation of possible environmental causes. Suspected variables were fog chemistry and frequency, rain chemistry, and ozone exposure. Significant (p = 0.05–0.01) spatial and temporal correlations of foliar browning with the fog frequency and fog chemistry variables have been detected, and their possible cause–effect relationship evaluated using both conventional on the ground sampling and remote sensing techniques. The use of remote sensing techniques, though not conclusive over the time it was carried out, did show the potential for future investigation of this type. In this study the deterioration of the two principal taxa, paper birch (Betulapapyrifera Marsh.) and mountain paper birch (Betulacordifolia Regel), were examined in terms of crown dieback and compared. These two taxa occur as separate stands or as a mixture in the birch plots. Comparisons of mortality responses of the two birch taxa together with results of leaf browning on transplanted young clones of the two taxa indicated a significantly (p < 0.001) greater sensitivity of B. cordifolia, whereas no significant differences between the taxa exist for percentage of trees with dieback. The potential role of sensitive indicators, such as B. cordifolia, as biomonitors of atmospheric change in an ecotonal situation like the Fundy coast is important, as these may give us the first indications of vegetation response to a changing chemical and physical environment.