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生长在由安大略前寒武纪地盾风化而来的贫瘠土壤上健康的和正在衰退的糖枫林,其树轮大小和化学性质被用来记载自1940年以来树木养分的变化历史。从1986年起,在Dorset每年可以观察到树木大幅度衰退的症状,在40年代期间形成的树轮其宽度已经减小,而1950年以后树轮大小和Ca、Mg、Mn的浓度均没有变化。但是,Ca浓度(680mg/kg)和Mg浓度(100mg/kg)已经属于最低糖枫树木的记录。Loring的糖枫比Dorset的要健康些,可在60年代也发生了树轮宽度减小现象,比Dorset晚减20年,并伴随着Ca和Mg浓度的显著降低,Mn浓度的降低尤为突出。微量元素或A1的毒性不可能是对衰减症状的直接响应。如果Loring是安大略中部看上去比较健康的糖枫林的代表地,那么在未来20年中,由养分短缺引起的衰退症状将更广泛地发生。
The healthy and decaying sugar maple forests, which grow on marginal soil weathered from the Precambrian shield in Ontario, have tree-ring sizes and chemical properties that document the history of tree nutrient changes since 1940. Since 1986, a dramatic decline of trees has been observed in Dorset each year, with the width of the tree-ring formed during the 1940s decreasing, and no change in tree-ring size and Ca, Mg, Mn concentrations after 1950 . However, Ca concentrations (680 mg / kg) and Mg concentrations (100 mg / kg) have been recorded by the lowest sugar maple trees. Loring’s sugar-maples were healthier than Dorset’s, and tree-ring width reductions also occurred in the 1960s, a 20-year reduction over Dorset, with a significant reduction in Ca and Mg concentrations, especially with reduced Mn concentrations. The toxicity of trace elements or A1 can not be a direct response to the attenuation of symptoms. If Loring is the center of Ontario’s seemingly healthier sugar maple, then recession symptoms caused by nutrient shortages will occur more widely in the next 20 years.