EFFECT OF DENSITY CONTROL AND UNDERCUTTING ON ROOT MORPHOLOGY OF 1- 5-YEAR FIELD PERFORMANCE OF ROOT-GRADED STOCK IN THE CENTRAL USA(0 BAREROOT HARDWOOD SEEDLINGS )

The Hardwood Quality Nursery Cooperative (bareroot forest nurseries in 5 midwestern states) initiated a series of studies in 1987 to evaluat e red oak (Quercus rubra L.), and black walnut (Juglans nigra L.) seed ling performance as a function of cultural treatments and seedling roo t system morphology. Seedlings were grown at three densities (32, 64, and 128 stems m(-2) for red oak; 32, 64, and 96 stems m(-2) for black walnut), and half of the density plots were undercut. Seedlings receiv ed fertilizer, weeding, and irrigation treatments customary to their r espective nurseries. Seedlings were lifted, measured, and outplanted i n their respective states as completely random individual tree plots d uring spring 1988. Survival, height, and diameter were evaluated annua lly through 1992. Seedling height, diameter, and number of permanent f irst-order lateral roots (FOLR) decreased with increasing bed density. At a given density, undercutting produced smaller seedlings (for both height and diameter) that had greater numbers of FOLR. Numbers of FOL R influenced seedling performance after outplanting. Red oak seedlings with at least 5 FOLR and black walnut with at least 7 FOLR had better survival and growth than seedlings with fewer roots.