Print PageThe process of ecological succession comprises an interconnected web of biotic and abiotic factors that both affect and respond to changes in the community, but historically the study of succession has focused on plants and left other essential organisms, such as ectomycorrhizal (EM) fungi, largely ignored. As the primary method used by most trees to acquire nutrients from the soil, the EM mutualism helps to shape the structure and composition of forest ecosystems. EM fungi are both phylogenetically and functionally diverse, and often show host preference for particular plant taxa, but the effects of host preference on interspecies competition between trees is not known. Fungal host preference may either facilitate or hinder the succession of dominant tree species. To address this question, a reciprocal transplant of white oak (Quercus alba) and loblolly pine (Pinus taeda) seedlings was conducted in paired plots of oak-dominated and pine-dominated forest in the Piedmont region of North Carolina. EM root tips were collected from seedlings and adults for molecular identification of fungal species based on sequence similarity of the internal transcribed spacer region of ribosomal DNA.
Results/Conclusions
Most individual seedlings hosted only 1-2 species of EM fungi, though the identities of these species varied widely among different seedlings within the same plot, indicating that seedling associations are primarily determined by the initial colonization of roots, rather than by any competitive advantage of seedling-adapted EM species. The fungal associations of adult trees determine which EM species are dominant in the soil and thus available for seedlings to associate with. Oak seedlings planted under pine proved significantly better able to form mycorrhizal associations with the available fungi than were pine seedlings planted under oak. The broad preference of oak seedlings may allow oaks to readily establish in mid-seral pine forests, facilitating succession.
