FOLIAR DEFICIENCIES OF SUGAR MAPLE STANDS ASSOCIATED WITH SOIL CATION IMBALANCES IN THE QUEBEC APPALACHIANS

Widespread symptoms of foliar deficiency of P and K have been observed for almost a decade in most of the declining hardwood forest in the Quebec Appalachians. We hypothesized that the foliar nutrient disturbances were related to the chemical equilibrium of exchangeable soil cations. Mature sugar maple (Acer saccharum Marsh.) foliage, and soil H-Ah and B horizon from 246 hardwood stands located in the Quebec Appalachians were sampled and analyzed. A cluster analysis using the Diagnosis and Recommendation Integrated System (DRIS) indices of the foliar data permitted the identification of six different nutritional groups: one slightly and one strongly deficient group in P-K, three groups having a K-Ca deficiency at different intensities from weak to strong, and one group having a strong P-K-Ca deficiency. These foliar nutrient status were strongly related to some soil properties. The P-K deficient groups had a 30% lower K saturation in the H-Ah horizon than the average level of the other groups, but a higher proportion of exchangeable Ca in the H-Ah and B horizon. For the four groups that were K-Ca deficient, increased nutrient stress was associated with reductions in soil Ca saturation and pH, and, particularly, increases in soil Mg saturation. Also, the Ca/(H + Al) ratio of exchangeable cations in the B horizon was less than or equal to 0.6 for these groups. High soil Mg saturation, potential soil Al toxicity related to low Ca saturation, and unfavorable soil humus properties were associated with the severity of nutrient stress. To obtain a balanced nutrition for sugar maple in this region, the forest humus should have less than 10% of Mg on exchange sites, a Ca/Mg ratio of exchangeable cations > 6, and a K/Mg ratio > 0.5. The values in the mineral B horizon should be < 10% for Mg/CEC, > 4 for the Ca/Mg ratio, > 1 for the K/Mg ratio, and > 1 for the Ca/(H + Al) ratio.