Relationship between the ectomycorrhizal fungus Pisolithus tinctorius associated with loblolly pine and acid-generating Thiobacillus spp. on an acidic strip mine site

Abstract

Loblolly pine seedlings were transplanted onto a pyritic coal mine site in a commercial reclamation effort. After 5 years, trees which became naturally infected with Pisolithus tinctorius, or other ectomycorrhizal fungi which produced sporocarps, were twice the height and stem diameter of trees not associated with sporocarps. The hypothesis that P. tinctorius promotes superior growth of its host by inhibiting the growth or activity of Thiobacillus ferrooxidans and T. thiooxidans, which catalyze production of sulfuric acid from pyrite, was examined. Soil pH was lower in the root zones of trees associated with P. tinctorius than with trees not associated with P. tinctorius, and sulfate was higher. Differences were not found in ferric or ferrous ions or in populations of the two bacterial species. Apparently P. tinctorius benefits its hosts by mechanisms other than inhibition of Thiobacillus spp.