Foliar nutrient variation and sampling intensity for Acerrubrum trees

Concentrations of N, P, K, Ca, and Mg were determined for red maple (Acerrubrum L.) foliage sampled during mid to late August. Samples of mature leaves were collected from the upper, middle, and lower crown on the north and south sides of 22 dominant and codominant red maple trees growing in 51- to 58-year-old even-aged stands on a good site (SI 50 = 21.6 m) and a poor site (SI 50 = 13.6 m) in northern Michigan. Although individual trees differed greatly in concentrations of all elements, trees growing on the good site had significantly higher foliar concentrations of P, Ca, and Mg than trees on the poor site. Concentrations of N and K were similar for both sites. Concentrations of N, P, K, and Ca also differed significantly with crown position, but no difference in concentration for any element was found with crown direction. The sample-size requirements are given for each element at a selected level of accuracy.