Growth, Xylem Pressure Potential, and Nutrient Absorption of Loblolly Pine on a Reclaimed Surface Mine as Affected by an Induced Pisolithus tinctorius Infection

The effects of Pisolithus tinctorius ectomycorrhizae on survival, growth, xylem pressure potential, and nutrient uptake of loblolly pine on a southern Appalachian coal surface mine were examined. One-year-old bareroot seedlings artificially inoculated with P. tinctorius and control seedlings with Thelephora terrestris ectomycorrhizae were outplanted on a surface-mined site in Tennessee. The site had previously been contoured and hydroseeded with a mixture of herbaceous ground cover species. A soil fertility variable was imposed in the study by broadcast fertilization at outplanting of one-half of the plots of each mycorrhizal treatment at the rate of 336 kg/ha NPK. After 7 years, survival and growth of trees previously inoculated with P. tinctorius were significantly improved relative to control trees. Fertilization elicited a significant reduction in survival and a negligible growth response in trees of both mycorrhizal treatments due primarily to its stimulation of competing herbaceous species. During the third growing season, xylem pressure potential of seedlings with P. tinctorius ectomycorrhizae was significantly less negative than that of control seedlings during a prolonged period of moisture stress. Analyses of foliar samples collected during the third growing season revealed that seedlings infected by P. tinctorius had more NO3 and less Zn in their needles than control seedlings. The results of this study provide evidence that the benefits afforded loblolly pine on surface mines by P. tinctorius ectomycorrhizae include enhanced absorption of water as well as increased uptake of nutrients, and these benefits are not compromised by the presence of competing herbaceous species. For. Sci. 35(2):569-581.