Mycorrhizae and Reforestation Success in the Oak-Hickory Region

Abstract

The potential for improving the growth of outplanted oak seedlings through the manipulation of mycorrhizal symbiosis is promising. However, only limited research has been conducted on the mycorrhizal relationships of commercially valuable oak species. This study was conducted to evaluate the role of mycorrhizal inoculation in an oak reforestation program.Black oak (Quercus velutina Lam.) seedlings inoculated with Pisolithus tinctorius (Pers.) Coker and Couch were grown for one season in Spencer-LeMaire containers in a glasshouse and in a nursery; noninoculated seedlings were also grown in containers and in the nursery for comparison. Examination of the inoculated stock before outplanting revealed that approximately 40 percent of the roots of the containerized and 1−0 bareroot seedlings were infected with P. tinctorius. Bare-root seedlings were significantly larger than container-grown seedlings. However, total root system length of the containerized seedlings was significantly greater.Two years after outplanting on two Missouri Ozark clearcut sites, shoot length, root collar diameter, and leaf area of the container-grown seedlings inoculated with P. tinctorius were greater than in the inoculated and noninoculated bare-root stock. The bareroot stock, regardless of inoculation treatment, suffered from repeated shoot dieback, and leaf area remained relatively small. Ectomycorrhizal infection of roots of the container-grown stock by P. tinctorius was 22 percent after one year in the field. During the same period of time ectomycorrhizal infection of the bareroot stock declined to 16 percent. Total root system length was significantly greater for P. tinctorius inoculated container-grown stock.Seasonal evaluation of seedling water relations indicated that containerized stock inoculated with P. tinctorius avoided water stress more effectively during a mild drought. Soil-plant liquid flow resistance was significantly lower in P. tinctorius inoculated seedlings than in noninoculated stock.