easily, and can also aid rooting by cutting through the tough sclerenchyma ring and/or lignified tissue which may be a physical barrier to adventitious root initiation (Hartmann et al., 1997).

A study of pecan stooling by Wood (1989) found that girdling was essential to rooting. Four-year-old pecan seedlings were severed 6 cm above the ground in February. In July, treatments were applied to shoots. The study was a 2 x 3 factorial, with girdled vs. non-girdled, and 0 IBA, 3000 ppm IBA, and 6000 ppm IBA being the treatment combinations. Shoots were girdled by cutting a 1 cm ring around the shoot with a knife. IBA was applied in a lanolin paste. Soil was mounded around the plants, and shoots were uncovered and evaluated in March. Girdled shoots with no IBA application reached 46% rooting, and 100% of girdled shoots treated with 3000 or 6000 ppm IBA in a lanolin paste produced roots. None of the ungirdled shoots rooted, regardless of IBA concentration. The author concluded that girdling triggered rooting in mound layered pecans, whereas IBA increased rooting percentages. Survival studies were also conducted, and it was found that ramets that had been girdled but had no IBA applied had the greatest survivability, at 83%, versus girdled shoots with 6000 ppm IBA at 45% survival and girdled shoots with 3000 ppm IBA at 33% survival after the first growing season.

A study by Dunn and Cole (1995) that examined mound layering of Pistachia chinensis Bunge. found that both wounding and auxin application were essential to rooting. Ten-month-old trees were cut back to 18 cm above the soil line in May. This study was a 2 x 2 factorial, with wounded or not wounded and 0 IBA or 17,500 ppm IBA being the two treatments. Wounding was performed by cutting into the shoot approximately 1mm deep. IBA was applied as a liquid solution rubbed into the wound. Sawdust was mounded around the shoots and they were uncovered in April. It was found that the treatment combination of wounding plus 17,500 ppm IBA was the most successful, while the other three treatment combinations were not significantly different from each other. In the two years the study was conducted, 77% and 75%, respectively, of wounded shoots treated with 17,500 ppm IBA produced roots. The authors concluded that wounding of shoots and auxin application were necessary for root production, but