Foliar and wood chemistry of sugar maple along a gradient of soil acidity and stand health

The decline of sugar maple (Acer saccharum Marsh.) in forest of north-eastern North America is an important environmental issue. In this study, relationships between, soil, wood and foliar chemistry were assessed for 17 stands distributed within a large area of the Quebec sugar maple forest and that were growing on soils with a strong gradient of acidity and base saturation. There were many significant relationships between variables describing the acid-base status of the top-B soil (Ca and Mg concentrations, exchangeable acidity and base saturation) and Ca and Mn concentrations and Ca/Mn and Mg/Mn in tree tissues. Manganese was the element that showed the strongest inverse non-linear relationships with top-B soil base saturation with variance explanation of 71 and 65%, for wood and foliage, respectively. The 17 sites were divided in two groups according to their level of decline. The declining stands had significantly higher wood Mn and Mg concentrations and lower Ca/Mn ratios and significantly higher foliar Mn and lower Ca and Al concentrations. It was impossible to determine if these differences were a cause or a symptom of sugar maple health. However, the increase in Mn concentrations in tree tissues with increasing soil acidity, as well as the higher Mn concentrations in declining as compared to healthy stands suggest that Mn, as well as low Ca availability, could be an important contributing factor in the sugar maple decline.