Litter layers (O-ie) as a calcium source of sugar maple seedlings in a northern hardwood forest

摘要

The role of the O-ie horizon in calcium supply of sugar maple (Acer saccharum Marsh.) seedlings was evaluated. Forest floor O-ie horizon was reciprocally transplanted on 1 m(2) quadrats between a Ca-treated (W1) and a reference (W3) watershed, and sugar maple seeds were planted on the quadrats. The Oie horizon in W1 exhibited a greatly increased Ca:Sr molar ratio compared with the reference W3 (550 vs. 220), allowing distinction of this Ca source in seedling tissues. Foliage and fine roots of maple seedlings growing on quadrats in W3 with O-ie transplanted from W1 exhibited Ca:Sr ratios intermediate between the O-ie and underlying native soil horizons, demonstrating the role of O-ie in seedling Ca nutrition. However, apparently strong and temporally changing discrimination of Ca and Sr in seedling uptake and internal transport confounded quantitative evaluation.