Responses of understory tree seedlings to alteration of the soil fungal community in mid- and late-successional forests

Abstract

To determine if soil fungi and overstory community composition influence survival and growth of understory tree seedlings, we planted Pinus taeda L., Quercus alba L. and Cornus florida L. seedlings in the understory of upland oak and upland pine forests at Savannah River Site, South Carolina. Fungicide was applied to the soil around half of the seedlings to alter composition of the soil fungal community. Soil collected from fungicide plots had significantly fewer colony forming units on agar than did controls. However, we detected no significant effect of fungicide on percent of seedling roots colonized by mycorrhizal fungi. By the end of two growing seasons, the largest differences in seedling performance were between tree species; Q. alba and P. taeda had significantly greater survival than did C. florida. Total biomass growth was greatest in Q. alba, and least in C. florida. Fungicide led to a significant increase in biomass growth in Q. alba, a significant decrease in growth in C. florida and no change in biomass growth of P. taeda. Overstory composition had no significant effect on either survival or growth of seedlings. In general, these results suggest that: (1) the composition of the soil fungal community can influence growth of understory seedlings in some tree species; and (2) planting can be used to establish advance regeneration of desirable species in upland forests of the southeastern USA.