Native mycorrhizal fungi replace introduced fungal species on Virginia pine and American chestnut planted on reclaimed mine sites of Ohio

Abstract

Plant-microbe community dynamics influence the natural succession of plant species where pioneer vegetation facilitates the establishment of a distantly related, later successional plant species. This has been observed in the case of restoration of the American chestnut (Castanea dentata) on abandoned mine land where Virginia pine (Pinus virginiana) facilitated the establishment of chestnut seedlings. This was apparently due to the natural mycorrhizal networks of pine, which aided the survival and growth of chestnut seedlings. In this study, we assessed the survival and propensity of introduced mycorrhizal fungi on Virginia pine to colonize pure American and backcrossed American chestnut. Seedlings were planted in Perry State Forest located in southeastern Ohio. This area was mined for coal in the 1950s and had very little reclamation done aside from experimental tree plantings. The selected site, with little topsoil or organic matter, was characterized by high concentrations of Al, high soil temperatures, and a pH of 3.6. Virginia pine seedlings were inoculated using ectomycorrhizal (ECM) cultures of Amanita rubescens, Laccaria laccata, and Pisolithus tinctorius via liquid media. After three months, roots were tested for the presence of mycorrhizae. They were then transplanted and grown for two years in the greenhouse. After verifying mycorrhizal colonization, 600 pines were out planted in May of 2005. Chestnut seedlings (100 one-year-old seedlings) inoculated with P. tinctorius by the Ohio state tree nursery had been planted by other researchers at the same time. After eight growing seasons, pines and chestnuts were measured and sampled for ECM colonization. Growth measurements showed that pines and hybrid chestnuts had significantly more aboveground biomass compared to pure American chestnut (P = 0.01). Eleven fungal species were detected using DNA sequencing. With the exception of Amanita, the inoculum that were out planted with both chestnut and Virginia pine were replaced after 8 field seasons by fungi native to the site. More fungal species were sampled from the Virginia pines than from chestnut roots, which contributed to the significant differences in ECM fungal community composition between the two species (P = 0.005).