Origin of the phosphorus deficiency observed in declining sugar maple stands in the Quebec Appalachians
To investigate the origin of the phosphorus (P) deficiency previously observed in declining sugar maple (Acersaccharum Marsh.) in several sites of the Quebec Appalachians, soils originating from 10 maple stands with foliar P concentrations ranging from 0.85 to 2.36 mg • g−1 were subjected to the following analyses: the chemical composition and P pools of L and F horizons, as well as pH, total nitrogen (N), exchangeable cations, total organic and inorganic P, P reserves fractionated according to their availability, and extractable iron (Fe) and aluminum (Al) of Ah (or H) and B horizons. The number of root tips per unit volume of soil was measured at 0–15 cm depth. Foliar P concentrations were positively correlated with P concentrations and P pools of L and F horizons, with the contents of readily available P fractions of the Ah or H horizon, and with the number of root tips to 15 cm depth. In contrast, foliar P concentrations and the available P fractions of the Ah or H horizon were negatively correlated with pH, with total P reserves, and with the concentrations of extractable Fe and Al and amorphous inorganic Fe of this horizon. The characteristics of the B horizon had little effect on P nutrition. It is concluded that under the conditions now prevailing in the Quebec Appalachians, the nature of the humus form may have a major influence on P nutrition of trees. Stands growing on soils with a moderately acid Ah horizon (mull) exhibited low foliar P concentrations, while those growing on soils associated with a mor humus had adequate P nutrition. A hypothesis is presented that may explain these unusual observations.