Nutrient stress predisposes and contributes to sugar maple dieback across its northern range: a review.

Over the last 60 years, multiple studies have attributed sugar maple (Acer saccharum Marsh.) dieback and decline to nutrient status, interaction and tree stress. Site differences in deficient, toxic or antagonistic levels of soil calcium, magnesium, phosphorus, potassium, manganese and aluminium are correlated with mortality and dieback in many studies. In general, a single nutrient is rarely determined to be responsible for poor sugar maple health. Other factors such as defoliation, management, climate fluctuations and soil biota can play key roles in dieback. Nutrient stresses can greatly increase the risk of injury and mortality from other biotic or abiotic stresses. Anthropogenic inputs and climate change may also cause perturbation of nutrient or pH thresholds for sugar maple. Therefore, historical sugar maple sites may no longer be suitable to support a healthy sugar maple forest under current management regimes. The following is a review of locations, symptoms and studies of the relationship of mineral stress to sugar maple health, which will be useful information for forest resource managers to consider when faced with maple health issues. Conclusions developed from this review are as follows: (1) land managers should consider soil nutrition in decision-making concerning sugar maple, (2) standardization of evaluation methods for tree nutrition is somewhat lacking and (3) additional multidisciplinary research is needed to clarify the interacting factors affecting sugar maple health and nutrition. [ABSTRACT FROM AUTHOR]