SHOOT AND FOLIAGE GROWTH PHENOLOGY OF LOBLOLLY-PINE TREES AS AFFECTEDBY NITROGEN-FERTILIZATION

Effects of N fertilization on shoot phenology and foliage production w ere determined in loblolly pine (Pinus taeda L.) trees growing in the Georgia Piedmont. Two rates of N fertilizer were applied in February 1 991. Shoot and foliage growth were determined at upper, middle, and lo wer crown positions at 1-month intervals throughout 1991. Shoot elonga tion of individual flushes overlapped, although there was about a I-mo nth delay between the initiation of each successive flush. Needle elon gation was closely associated with shoot elongation but lasted 2 month s longer. On average, the first flush contributed about 69% to total l eaf area. Shoot and foliage growth increased with crown height. Shoot elongation, needle length, number of fascicles per flush, and leaf are a per flush were 9.7, 1.4, 4.7, and 6.9 times higher, respectively, in the upper crown than in the lower crown. The effects of N fertilizati on on shoot and foliage growth were most pronounced in the middle crow n position. Leaf area production per shoot was increased by 12.4, 66.4 , and 41.1% by fertilization for shoots in the upper, middle, and lowe r crowns, respectively. N fertilization did not alter the seasonal pat terns of shoot and foliage development Both fertilized and control tre es began, peaked, and ended flush and fascicle elongation concurrently .