. Annual program report, 1989. Acidic Precipitation in Ontario Study; Acid precipitation (Meteorology); Acid pollution of rivers, lakes, etc; Acid rain. - 11 province as well as the Niagara and Muskoka areas. Dieback is scattered through the northern part of the study area while there is a broad band of relatively healthy hardwood stands extending from Lake Huron south of Georgian Bay east to the Ottawa area. No pattern of dieback was seen that could be directly related to acidic precipitation patterns; however, soil characteristics, particularly higher buffering potential of limestone- based
. Annual program report, 1989. Acidic Precipitation in Ontario Study; Acid precipitation (Meteorology); Acid pollution of rivers, lakes, etc; Acid rain. - 11 province as well as the Niagara and Muskoka areas. Dieback is scattered through the northern part of the study area while there is a broad band of relatively healthy hardwood stands extending from Lake Huron south of Georgian Bay east to the Ottawa area. No pattern of dieback was seen that could be directly related to acidic precipitation patterns; however, soil characteristics, particularly higher buffering potential of limestone- based soils, may have an important role in the distribution of the problem sites. The severity and extent of dieback was greatest where soil was most sensitive and deposition was highest. In 1987, the plots were re-examined to determine whether the condition of the trees as measured by the Decline Index had changed. The 1987 survey identified plots in the regions of Algonquin, Parry Sound, Muskoka, Niagara, London, Cornwall and the north shore of Lake Huron where the Decline Index was higher then in 1986. These areas correspond to known or suspected forest insect infestations. For the majority of the plots not affected by defoliating insects, the mean Decline Index of trees did not change by more than one standard deviation between 1986 and 1987. There was no evidence of a relationship between tree decline and wet sulphate deposition patterns. Changes in decline indices from 1986 to 1987 are shown in Figure Figure 20. Changes in sugar maple decline indices from 1986 to 1987 for Hardwood Decline Survey plots in Ontario. Changes in Decline Index o decrease > (1 ) + little change (1 ). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Acidic Precipitation in Ontario Study; Ontario. Ministry of t
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