Distribution of Area Increment Over the Bole of Fertilized Douglas-Fir

Abstract

Consideration is given to the distribution of growth increment at 6 points up the stem of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) 5 years after fertilization. The fully stocked stand, near Port Alberni, B.C., was 49 years old with heights and diameters reaching 100 ft and 20 in. respectively when fertilized with 220 and 440 lb/acre of urea. No change of consequence occurred in tree form in the codominant and intermediate crown classes as a result of the volume response which was still evident, although greatly diminished, after 5 years. In dominant trees, however, cross-sectional area growth in the central third of the stem was less than the controls even though other parts of the bole showed a positive response which lasted until the 4th year. The net volume response was negligible. The estimation of volume response to fertilization in dominant trees from breast-height measurements should possibly be approached with caution.