Effect of crown position on foliar concentrations of 11 elements in Acer saccharum and Betula alleghaniensis trees on a till soil

Concentrations of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, and Na were examined in whole leaves collected in August 1981 from specified positions within the crowns of 15 Acersaccharum Marsh, and 10 Betulaalleghaniensis Britton trees growing in closed forest on a Precambrian-derived till soil in northern Ontario. Concentrations of K, Ca, Mg, Fe, Zn, and Na were significantly higher in lower crown leaves of A. saccharum, and Ca was significantly higher in lower crown leaves of B. alleghaniensis, but in other elements there were no significant differences attributable to crown position. There was a tendency for element concentrations to be higher at all crown positions in intermediate as opposed to codominant trees; however, differences were not significant or were weakly significant at best. Tree-to-tree variation was less in mid- and lower-crown, as opposed to upper-crown, foliage. Generally, for both species, to bring standard errors to within ± 10% of the group mean, about 30 trees per stand should be sampled if analyses are restricted to N, P, K, Ca, Mg, and 40–70 trees per stand should be sampled if trace elements such as Mn are to be included.